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Responses of native legume desert trees used for reforestation in the Sonoran Desert to plant growth-promoting microorganisms in screen house
Abstract
Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico
and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria
(Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite
amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10months of cultivation.
Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured
as transpiration and diffusive resistance, when these trees were cultivated without water restrictions.
... Restoration of arid lands that is not used for agriculture, using plant growth-promoting bacteria (PGPB) alone or combined with mycorrhizae fungi (AM-fungi) was done experimentally on a relatively small scale in studies conducted mainly in pots under controlled or semi-controlled conditions (de-Bashan et al. 2012;Medina and Azcón 2012). Studies were mainly concentrated in southern Spain (Requena et al. 1997(Requena et al. , 2001Valdenegro et al. 2001;Medina et al. 2004a;Marulanda et al. 2009;Benabdellah et al. 2011;Armada et al. 2014a;Mengual et al. 2014a;Ortiz et al. 2015), Mexico (Puente and Bashan 1993;Bashan et al. 1999Bashan et al. , 2009aBashan et al. , b, 2012Carrillo-Garcia et al. 2000a;Toledo et al. 2001;Carrillo et al. 2002;Puente et al. 2004Puente et al. , 2009Bacilio et al. 2006Bacilio et al. , 2011Leyva and Bashan 2008;Lopez et al. 2012), west Africa (Founoune et al. 2002;Duponnois and Plenchette 2003), USA (Grandlic et al. 2008;de-Bashan et al. 2010a, b), Argentina (Felker et al. 2005) and India (Ramachandran and Radhapriya 2016). Because evaluation of success of field studies is a long-term task, there are fewer studies (Requena et al. 2001;Gao et al. 2002;Vovides et al. 2011;Lopez-Lozano et al. 2016). ...
... The development of all plants was monitored every six months for 30 months. Inoculation with PGPB and compost amendment differentially supported growth of these plants but not all plant parameters are supported equally (Bashan et al. 2009a. Since 2009, the experimental field was unattended, except maintaining fencing against large grazers. ...
... Production of AM fungi and compost, plant propagation in nurseries, preparation of the field, and special protections against herbivores were described in previous publications (Bashan et al. 2009a, b;. ...
Background and aims
Restoration of degraded desert soil with three species of legume trees and the giant cardon cactus was evaluated 11 years after planting in the southern Sonora Desert.
Methods
The trees in six independent field experiments were grown individually or in combination of a legume tree and cardon cactus and were originally treated with plant growth-promoting bacteria, arbuscular mycorrhizal fungi, or small amounts of cattle compost or a combination of all treatments. Survival and height of trees and cacti and cactus biovolume were measured.
Results
When data were combined from all experiments and analyzed together, the best survivor was the cardon cacti and, to a lesser extent, the legume tree mesquite amargo. Over a decade later, a combination of a legume tree with cardon cactus, while detrimental to the legume, significantly increased the chances of the cactus to survive and grow in degraded soil. The biotic and compost treatments, while enhancing the initial establishment of the plants in 2004, had only marginal benefit on the growth of cactus 11 years later.
Conclusions
Long-term desert restoration with native trees is possible. Because this cactus is the native, long term soil stabilizer, a combination cactus-legume tree is recommended for long term desert restorations.
... It is very difficult to recover all these attributes after severe perturbation, in part because natural revegetation in highly disturbed areas is very slow, especially in arid lands. A shortcut strategy to long vegetative succession process and promote the potential return of most of the original attributes requires establishment of climax plants to accelerate revegetation (Moore and Russell 1990;Bashan et al. 2009a, b). ...
... To address the question of impact of restoration on potential nitrogen fixation in arid zone, we analyzed a specific case of field restoration with trees/shrubs and cacti which started 10 years ago (Bashan et al. 2009a, b;. We hypothesized that the N 2 -fixing community of rhizosphere soil samples from a long-term successfully restored area would resemble those of undisturbed soil regarding microbial abundance, diversity, and potential N 2 -fixing activity and be greater than those microbial communities in disturbed soils. ...
... The site was maintained until 2009 by eliminating invasive grasses, excluding cattle, and preventing soil erosion; it was abandoned since then. Soil characteristics and the seven restoration trials were described in detail by Bashan et al. (2009a, b;. Because the area is part of a protected natural reserve, there has been no impact by humans or free-ranging cattle for 10 years. ...
Background and aims
A major problem in all restoration and rehabilitation projects is to restore the function of the ecosystem. Nitrogen, next to water, is the most limiting factor for productivity of arid terrestrial ecosystems.
Methods
We used a successful restored area, completed 10 years earlier, in comparison with an undisturbed scrubland area and a remaining, disturbed area in the southern Sonoran Desert in Baja California, Mexico. We compared the abundance of the nifH gene, estimated by qPCR, potential N2 fixation activity by acetylene reduction assay, and diversity of diazotrophs by denaturing gradient gel electrophoresis in the rhizosphere of the most representative plant species, the cardon cactus and the mesquite used for restoration.
Results
The abundance of N2-fixing bacteria in the rhizosphere of cardon growing with mesquite had significantly higher abundance of nifH gene than the rhizosphere of cardon that grew separately. Across all samples, the potential N2 fixation was significantly higher in soil samples from the restored site than samples from the undisturbed and disturbed sites.
Conclusions
Successful long-term restoration improved the potential N2 fixation to a level similar to undisturbed lands. Beneficial interactions between cardon and mesquite are a promising venue for desert reforestation by their contribution to improve N2 fixing potential in degraded arid lands and increasing the population of diazotrophs.
... The management of selected and appropriate plant growth promoting microorganisms (PGPM) can help plants to grow and to promote the stabilization of a self-sustaining ecosystem under stress conditions. Arbuscular mycorrhizal (AM) fungi enable plants to cope with drought stress not only by alleviating nutrient deficiencies but also by improving drought tolerance overcoming the detrimental effect of water and nutrient limitations (Augé, 2000(Augé, , 2004Bashan et al., 2009;Medina et al., 2003). Plant nutrients and water deficit are common stresses affecting plant survival and development in arid and semiarid areas. ...
... Thus, the improvement of nutrients and water uptake is important for plants growing under stressed conditions. Detrimental environmental conditions also negatively affect the survival and activity of rhizosphere microorganisms but those autochthonous adapted to adverse conditions (such as water limitation and nutrient deficiencies) may be the best candidates to be used as inocula to compensate in inoculated plants such stress conditions (Bashan et al., 2009;Marulanda et al., 2007;Marulanda-Aguirre et al., 2008). ...
... From this previous study under sterile conditions Bacillus megaterium resulted the most efficient bacteria in alleviating plant drought symptoms when applied alone or associated with each one of the three different autochthonous AM fungi (Marulanda et al., 2009). Authors concluded that microbial activities of adapted bacterial and fungal strains may exert a beneficial interactive effect on plant growth under drought conditions as also reported Bashan et al. (2009). In fact autochthonous AM fungi and bacteria populations naturally growing in arid soils have developed the ability to survive in water limited soils and are adapted to drought conditions . ...
This study investigated the effectiveness of several microorganisms, such as a Bacillus megaterium strain and/or an autochthonous consortium of arbuscular mycorrhizal fungi (AMF) on plant growth and drought tolerance in a natural semiarid soil. The effect of treated Aspergillus niger residue from sugar beet was also evaluated in non-inoculated and inoculated plants. Results from three successive harvests allowed us to determine the persistence along the time of beneficial effects of these treatments under natural drought conditions. Biomass production and nutrition were more increased by the transformed residue than concomitantly decreased antioxidant enzymatic activities under drought. The microbial inoculants assayed contributed to plant drought tolerance through strategies such as increased nutrition (particularly K+), hydric content and by decreasing stomatal conductance and antioxidant enzymatic activities. Similar microbial-mediated effects were confirmed at each harvest. The effectiveness of bacterial inoculation under drought conditions in natural soil has been almost unexplored. Here, the interactive effect of these bacteria with an AMF consortium maximized plant growth, water content and C, K, Ca and Mg content A relevant result is the greater effectiveness of the bacteria when inoculated in residue amended soil that promoted plant growth and hydric content and decreased most antioxidant activities to a greater extent than AMF inoculation. B. megaterium (without compost) also affected root growth, physiological and biochemical plant values involved in the adaptative plant drought response. The ability of B. megaterium in axenic medium to maintain indole acetic acid (IAA) like molecules and to increase proline production under osmotic stress conditions indicated the drought tolerance of this strain. In this study the management of natural resources, such as selected and drought adapted soil microorganisms and A. niger treated agrowaste resulted determinant for enhancing plant performance in an arid degraded soil.
... When mature, its main role is as the dominant tree in resource island formation and, therefore, directly contributes to the natural vegetation of these deserts and well-being of the desert. Its role as a common source of charcoal makes it a candidate for desert restoration (Moreno et al., 2017), a trend that gained momentum during the last decade, using many species of desert plants (Armada et al., 2014;Bacilio et al., 2006;Bashan et al., , 2009aBashan et al., ,b, 2012de-Bashan et al., 2010;Felker et al., 2005;Founoune et al., 2002;Gao et al., 2002;Grandlic et al., 2008;Medina et al., 2004;Mengual et al., 2014a,b;Puente et al., 1999;Requena et al., 2001;Toledo et al., 1995;Valdenegro et al., 2001;Vovides et al., 2011). ...
... This includes cultivating mesquite in hydroponic growth solution (Leyva and Bashan, 2008), in small growth cell masses (Dominguez-Nuñez et al., 2012), or root cuttings dipped in bacteria culture (Spiekermannm et al., 1999). All these studies used inoculation without any formulation of the culture medium or formulated into macro-beads of alginate (2-3 mm in dia.) together with Bacillus pumilus, AM fungi, and compost in screen houses (Bashan et al., 2009a), or in the field (Bashan et al., 2012;Lopez-Lozano et al., 2016;Moreno et al., 2017). However, long-term greenhouse and field experiments (1-E12 years) did not measure the shorter net effect of formulated A. brasilense for mesquite seedling production for a duration of about six months, common for production of transplants in nurseries. ...
Massive clear-cutting of wild stands of mesquite trees in the Mexican part of the Sonoran Desert result from high demand for this wood by the charcoal industry. Consequently, there is a need to develop techniques for reforestation of this tree in the desert and maintain its natural diversity at the same time. An outdoor nursery procedure to produce mesquite transplants from diversely originated seeds for reforestation of arid zones was developed. This procedure involved: 1) inoculation of the seedlings in the nursery with the plant growth-promoting bacteria (PGPB) Azospirillum brasilense immobilized in dry microbeads of alginate, and 2) developing a reliable way to monitor plant development and aerial volume in the nursery for the entire growth period of seven months before transplantation. Dry microbeads containing the PGPB and maintained at room temperature were tested for survival of bacteria for up to seven months. These dry microbeads maintained sufficient population levels of A. brasilense to inoculate the plant for the entire period. Inoculation with the PGPB enhanced all growth parameters of the plants, including biomass, aerial volume, root system, and chlorophyll pigments, but not the auxiliary photosynthetic pigments. The PGPB was specifically identified colonizing the roots of the transplants by fluorescent in situ hybridization for the entire growth period. Measuring a few simple parameters allowed development of a workable model for plant growth. This model was confirmed by data obtained from sacrificed plants whose parameters were measured directly. This study shows that outdoor nursery cultivation of inoculated mesquite transplants is feasible.
... Other examples include India, where native trees inoculated with a consortium of PGPB performed well in degraded parkland soil ( Ramachandran & Radhapriya, 2016) and China, where rock-weathering bacteria supported plant growth ( Wu et al., 2017). In the southern Sonoran Desert of Mexico and in Argentina, inoculation with the agricultural PGPB species A. brasilense significantly promoted the growth, establishment, and survival of several legume trees and cacti ( Puente & Bashan, 1993;, Bashan et al., 2009a, Bashan et al., 2009bCarrillo-Garcia et al., 2000;Carrillo et al., 2002;Felker et al., 2005;Bacilio et al., 2006;Leyva & Bashan, 2008;Bashan et al., 2012). Other desert PGPB, both rhizospheric and endophytic, promoted the growth of cacti of varying sizes ( Puente et al., 2004, Puente et al., 2009Lopez et al., 2012). ...
... All rights reserved. Although this study was conducted under desert climatic conditions, by default, it was more protected than plants directly transplanted into desert soil having high herbivore pressure, local pests, and humane activity ( Bashan et al., 2009a;Bashan et al., 2012). Moreover, the size of the pots may be a limiting factor. ...
Soil degradation is an ecological disturbance, usually human-caused, that negatively affects the vegetation and climate of an ecosystem, particularly arid and semi-arid environments. These degraded soils can be restored by using native perennial plants inoculated with specific microorganisms. We studied the changes in root growth and the rhizosphere bacterial community of mesquite seedlings (Prosopis articulata) after inoculation with the endophytic bacteria Bacillus pumilus ES4, over three cycles of growth in the same soil under desert climatic conditions and found that inoculation significantly enhanced root biomass during the growth cycles, but not shoot biomass or root and shoot lengths. FISH analysis demonstrated that B. pumilus colonized the root cap, apical meristem, and elongation zone, forming small colonies, on roots from soil-grown mesquite. Inoculation also significantly changed the bacterial community structure of rhizophere and non-rhizosphere (without plants) soils based on DGGE profiles. The changes were highly stable and the bacterial community structure was maintained throughout the experimental period and not affected by plant replacement. 16S rRNA pyrosequencing confirmed the changes on structure of bacterial community and revealed an impact on the top taxonomic levels analyzed. The rhizospheres of inoculated plants showed a significant increase in the abundance of Proteobacteria and Acidobacteria coupled with a concomitant decrease in Actinobacteria, whereas an opposite response was observed in non-rhizospheric degraded soils. Overall, inoculation with B. pumilus reduced bacterial diversity, but increased the Rhizobium population in the soil. The class Bacilli, despite B. pumilis inoculum, showed minimal variation. (241 words)
... Application of microbead alginate formulations to inoculate plants in soils includes: (1) using several transplanted desert tree species and cacti in desert reforestation programs. These successful long-term shade house (8 months) and fi eld experiments (11 years, to 2015) used the PGPB/PGPR Azospirillum brasilense and phosphate-solubilizing B. pumilus entrapped in microbeads, where the inoculant was added to the planting holes beneath the root balls (Bashan et al. 2009a(Bashan et al. , b , 2012. ...
... A similar microbead formulation used for desert reforestation with leguminous trees was air-dried in fl at trays at 30 °C for 24 h without losing effi cacy. The resulting effect lasted for several years in the fi eld (Bashan et al. 2009a(Bashan et al. , b , 2012. The effi cacy of freeze-dried alginate beads was tested with an agricultural strain of Pantoea agglomerans . ...
Plants have been inoculated with plant growth-promoting microorganisms to enhance crop yield and performance over four decades. The two central aspects for success of inoculation are the effectiveness of the bacterial strain and the application technology. This chapter discusses characteristics of ideal carriers for bacterial inoculants [plant growth-promoting bacteria (PGPB) and plant growth-promoting rhizobacteria (PGPR)] and focuses on superior formulations for the future, mainly polymeric and encapsulated formulations and new emerging ideas in the field of inoculation. Future research avenues are highlighted.
... After cultivation for 10 months, survival of the latter two species was >80% and mesquite was almost 100%. Inoculation with growthpromoting microorganisms induce significant effects on the gas exchange of leaves of these trees, measured as transpiration and diffusion resistance, when these trees were cultivated without water restrictions (Bashan et al., 2009b). In the field, using the same combination of inoculants as in the greenhouse trials, seven field trials were undertaken with cardon cacti and three species of leguminous trees. ...
... Furthermore, over time, even plants without inoculation of AM fungi become mycorrhizal because there are sufficient indigenousBashan et al., 2000b). The additional treatments had a synergistic effect only in the case of mesquite, the most common nurse tree for cardon (Bashan et al., 2009b). In other field experiments, survival of the three leguminous trees (mesquite and two species of palo verde) was marginally affected by supplements after 30 months; survival was in the range of 60–90% of the trees, depending on the species, where all young trees survived >3 months under cultivation. ...
Plant growth-promoting bacteria (PGPB) of the genus Azospirillum are commonly used to improve agricultural plant yields. In addition to their usefulness as an agricultural inoculant, their potential benefits can be extended to environmental applications. For example, Azospirillum species can enhance the bioremediation of wastewater by microalgae by increasing algal proliferation and metabolism. Azospirillum species may improve the reforestation of marine mangrove trees, thereby enhancing fisheries along tropical coasts and may prevent desert soil erosion and promote abatement of dust pollution by assisting in the growth of cactus species. The following minireview discusses these applications, and shows future potential avenues for Azospirillum as an environmentally friendly microorganism.
... Although there are numerous studies on the effects of A. brasilense in improving the performance of agricultural crops (Okon and Lavandera-Gonzalez, 1994;Bashan et al. 2004), there is a lack of knowledge regarding its effect on forest plants Puente et al., 1999;Bacilio et al., 2006;Leyva and Bashan, 2008;Bashan et al., 2009) or its application in agroforestry systems. ...
... In the scientific literature, A. brasilense inoculation caused the highest plant yields under suboptimal environmental conditions for plant development, such as nutrient deficiencies or water stress, usually in arid or semiarid areas (Bashan and Holguin, 1997). Other studies have also shown that under water stress conditions, the activity of A. brasilense can improve growth and stabilise the maintenance of physiological conditions in the host plants (Alvarez et al. 1996;Bashan et al., 2009). However, this trial was conducted under non-restrictive water conditions suitable for plant growth in a forest nursery, under which the promotion of seedling growth, by different mechanisms, was observed. ...
Inoculation of mycorrhizal fungi and rhizobacteria in plants can improve their growth and physiological status, which could be particularly important for agricultural and forestry plants used for the revegetation of arid areas. Prosopis juliflora is a forest pioneer species that is drought resistant and has multiple uses (fodder, shade and shelter for livestock; timber and firewood, live fences and windbreaks in agroforestry systems). Azospirillum brasilense is a rhizobacterium that improves the growth of many agricultural crops. The hypothesis of this study was that P. juliflora seedlings produced in the nursery can respond positively to inoculation with A. brasilense CECT 590. Five months after inoculation, we examined the growth, water relations (osmotic potential at full turgor, osmotic potential at zero turgor, and the modulus of elasticity at full turgor), and concentration and content of macronutrients (N, P, K, Ca and Mg) in the seedlings. Subsequently, a trial was conducted to analyse root growth potential. A. brasilense CECT 590 inoculation caused an osmotic adjustment in P. juliflora seedlings but decreased the elasticity of the cell walls. Inoculation with A. brasilense CECT 590 significantly improved plant growth due in part to an increase of N concentration in the seedlings. A. brasilense CECT 590 inoculation also caused an increase in the root growth potential. The increased growth of P. juliflora seedlings inoculated with A. brasilense
was probably caused by more than one mechanism. Inoculation with A. brasilense at the nursery may be a suitable technique for producing improved seedling material for restoration purposes.
... However, inoculation with PGPR has the potential to reduce the negative effects of N restriction (Oliveira et al., 2003(Oliveira et al., , 2017Calzavara et al., 2018). Despite experiments with tree species in reforestation programs in desert areas (Bashan et al., 2009a(Bashan et al., ,b, 2012 and research on inoculation with bacteria in seedlings of trees of the Atlantic Biome (Tiepo et al., 2018), which demonstrate the efficiency of PGPR, there are no studies relating the effects of N restriction with inoculation with PGPR on the metabolism and growth of tree species of the Atlantic Forest. Such studies could provide vital information for forest restoration programs. ...
Nitrogen (N) deficiency generally affects plant physiology, influencing N metabolism and inhibiting photosynthesis and plant growth. The association with plant growth-promoting rhizobacteria (PGPR) can mitigate environmental stresses, such as N deficiency. No studies have examined whether inoculation with PGPR may counterbalance the effects of N restriction on the metabolism and growth of neotropical tree seedlings with different resource-use strategies. The current study aimed to determine the effects of inoculation with PGPR on the tolerance of seedlings of tree species submitted to N deficiency. Two species with acquisitive (Cecropia pachystachya and Heliocarpus popayanensis) and conservative (Cariniana estrellensis and Cabralea canjerana) resource-use strategies were chosen. The strains Ab-V5, of Azospirillum brasilense, and ZK, of Bacillus velezensis, were selected as PGPR for inoculation. Seedlings of the four plant species were grown in a mixture of soil and sand with (N+) or without (N-) N supplementation. The seedlings were also inoculated with Ab-V5 or ZK strains and, as a control, for each N treatment, some of the seedlings were not inoculated with PGPR (Nin). Thus, we assessed the effects of N deficiency, inoculation, and the interaction between these two factors on N metabolism, photosynthetic, and growth variables. Nitrogen deficiency limited photosynthesis in all plant species, in addition to decreasing the concentration of amino acids and proteins and the activity of enzymes of N metabolism. Only the growth of C. canjerana was not inhibited by N restriction. Inoculation with Ab-V5 led to increased growth of C. pachystachya seedlings, which was more pronounced under N supplementation (+70% of total dry mass). The association with PGPR decreased nitrate reductase activity (-52%) and increased glutamine synthetase activity (+370%) in the leaves, among other changes in N metabolism. The growth of H. popayanensis and C. estrellensis seedlings was not affected by inoculation, but metabolic variables in these species were influenced by inoculation with ZK. Photosynthesis increased with inoculation with ZK in H. popayanensis and with Ab-V5 in C. estrellensis. In C. canjerana, both PGPR promoted seedling growth (+11% of total dry mass). Nitrogen deficiency and inoculation with PGPR influence photosynthesis, growth, and N metabolism of seedlings of tree species that occur in the semideciduous seasonal forest. Moreover, the effects of inoculation are influenced by N supplementation during cultivation. The positive effects of PGPR on growth were higher in N-supplemented seedlings. Regardless of the functional group, inoculation with PGPR of seedlings of tree species of the Atlantic biome stimulates growth and development in optimal N conditions and increases tolerance to N restriction.
... Éstos valores indican que los efectos benéf icos de los microrganismos pueden tener un papel principal en las diferentes fases vegetativas, como es el proceso de la germinación (Kim y Weber, 1985). Resultados similares se han obtenido en otras investigaciones, aunque estas han sido en diferentes especies de plantas y otro tipo de bacterias benéf icas (Bashan et al., 2009;Villegas et al., 2010;Rueda et al., 2013), sumándose aquellos de Reyes-Pérez et al. (2018, al utilizar abonos orgánicos, rubros que demanda una agricultura sustentable a nivel mundial. Los resultados obtenidos en el trabajo, amplían los trabajos con cultivos agrícolas y sumándose a los de maíz (Peña-Datoli et al., 2016), el tabaco (González-Gómez et al., 2017) ...
Mexico currently ranks the fourth place in sorghum production worldwide. In Sonora State, this crop is one of the most productive. The Mayos, Amerindian people that live in the south of Sonora, Mexico have been promoting sustainable agricultural production systems. The application of bioderivatives of crustacean exoskeletons such as chitosan (QUI) as well as microorganisms that promote plant growth, and endomycorrhizal, symbiont, beneficial and antagonist microorganisms in some crops have shown to be an alternative in the process of germination and to improve crop yields. However, studies that assess the effect of bioderivative protocols such as QUI and microbial supplies are limited for the sorghum grain. Therefore, objective of our research was to evaluate sorghum grain, the effect of chitosan (100 and 50%), and a microbial complex (combined with QUI and individual forms) vs traditional fertilization in the Mayo indigenous region, Basconcobe, Etchojoa, Sonora, in the phenological induction, yield and protein quality of the grain. A randomized experimental block design was conducted with seven treatments and five repetitions. The following response variables were measured: germination rate, total chlorophyll, plant height during physiological maturity, panicle length, yield ha-1 and grain protein. The results indicated that in terms of yield and protein quality of sorghum grain, the most efficient treatment (with P < 0.05) consisted of 100% QUI + microbial consortium using 50% of regional fertilization. These results indicate that it is possible to employ chitosan as a biofertilizer of marine origin combined with a microbial fertilizer in a sorghum production system.
... His studies focused on the Sonoran Desert (Mexico), where agriculture is limited, but environmental problems such as desertification, loss of soil fertility, and lack of water are pervasive. Years of fundamental studies on the microbiology of the desert and the effect of PGPB and mycorrhizae on the establishment and growth of native plants, including the climax plant giant cardon cactus, resulted in long-term field experiments of restoration, and a set of manuscripts documenting the success (Bashan et al. 2009a(Bashan et al. , 2009bLopez-Lozano et al. 2016;Moreno et al. 2017). ...
... The combined application of AMF and fertilization improved plant behavior with PL inoculum, but not with CB inoculum or their mixture (Fig. 1). Growth stimulus by AMF was also observed by Bashan et al. (2009), who evaluated three legume species inoculated with AMF, and obtained positive responses for total height, number of branches, and stem thickness. Furthermore, Martin and Stutz (1994) found that inoculation of P. alba with Glomus intraradices under optimum production conditions (irrigation and fertilization) modified the root morphology (shorter, thicker and less branched roots) without affecting growth; the authors attributed these results to the role of AMF in substituting for fine feeder roots, which makes P. alba allocate more energy resources to increase aerial biomass. ...
Prosopis alba Griseb. (algarrobo blanco) is an important tree legume in semiarid regions of South America. Under field conditions, their seedlings are subjected to a wide range of environmental conditions that might produce stress, reducing their survival and/or growth. The aim of this work was to evaluate the combined effect of two native arbuscular mycorrhizal fungi (AMF) inocula and fertilization on growth variables of P. alba seedlings under nursery conditions and after drought stress. P. alba seedlings received different levels of basic fertilization (0%, 25% and 100%) and were inoculated with native AMF isolated from different rainfall regions of Parque Chaqueño Argentino: Colonia Benítez (CB, 1300 mm rainfall) and Padre Lozano (PL, 650 mm rainfall) or a mixture of both inocula (MIX), while the control group remained uninoculated. The combined application of native AMF and fertilization did not affect mycorrhizal colonization but allowed the formation of the different AMF structures. Moreover, when comparing the PL inoculum from a low rainfall region with other treatments, it significantly increased growth and development under nursery conditions and drought stress tolerance in the greenhouse. Therefore, AMF benefits for P. alba were related to inoculum source, being improved by the application of low fertilizer rates. This work supports the development of sustainable P. alba seedlings production and their field establishment under symbiotic conditions with native AMF.
... Notably, studies demonstrate that commercially available plant growth-promoting bacteria have limited capacity to rehabilitate degraded soil, in contrast to indigenous bacteria well adapted to the local environment (Bashan et al. 2009;García. 2004;Radhapriya et al. 2015). ...
The present study was aimed to isolate indigenous plant growth-promoting bacteria (PGPB) from Nanmangalam reserve forest, India and to analyze their positive impact on nursery plant species. In total, 160 isolates were obtained from different nitrogen-free Media (LGI, JMV, NFB). Amongst these, 12 isolates were shown positive for 5–8% of ammonia production nif H positive and then isolates were further tested for their plant growth-promoting (PGP) activity. Based on their PGP activity, nine isolates were selected, and applied in nurseries of twelve native plant species, along with organic manure and inorganic fertilizer. All the isolates were shown positive effects when compared to control. In that, five of these bacterial isolates, Paenibacillus sp. RRB2, Azospirillum brasilense RRAK5, Bacillus subtilis subsp. subtilis RRD8, Burholdria kururiensis RRAK1, and Pseudomonas stutzeri RRAN2, enhanced biomass production in several trees.
... Researches targeting the development of microbial consortia involving microbial members responsible for nitrogen fixation, phosphorus solubilization, siderophore production, phytohormone synthesis, biological crust formation that would finally support plant growth in symbiotic or non-symbiotic manner could help develop microbe-based strategies for carbon sequestration. Restoration of Sonoran Desert has been demonstrated by bioaugmentation of PGPB formulation consisting of Azospirillum brasilense and Bacillus pumilus, along with arbuscular mycorrhizal fungi and compost 66,67 . However, the plant growth response depends on the varying degrees of bio-formulation application. ...
Increasing levels of carbon dioxide (CO2) in the atmosphere are causing serious effect on climatic changes. Thereby the most concerned environmental issue is global warming these days. The same culprit carbon dioxide is also involved in the most important process called autotrophy, which supports life on earth. Autotrophy could be one of the probable answers for the management of atmospheric CO2 in an eco-friendly manner. Plants contribute a major part in CO2 fixation but often ignored microbes are also involved in CO2 fixation by different CO2 fixation pathways. Since desert represents sparse green cover, we cannot ignore the microbes present in such soil, which would be contributing for carbon fixation. Oligotrophic soil like desert harbours microbes that are capable of surviving in low-carbon conditions, thus opening an area of research for the study of CO2 fixation by oligotrophs. Since microbes require carbon for their growth, and hence under carbon starvation, they might have the mechanism for autotrophy. By exploring CO2 fixation through oligotrophs of desert, we could probably enrich the desert soil by carbon in near future. Such microbe-based CO2 fixation studies could help us to channelize CO2 for the synthesis of some important bioproducts.
... Our results show that inoculation can improve growth and quality of A. auriculiformis seedlings under experimental conditions. This supports the hypothesis that tree legumes are generally dependent on microsymbionts and other soil microorganisms to thrive in stressed soils (Bashan et al. 2009;Khan et al. 2014). Most previous studies investigating the interactive influence of AM fungi and PSB on plant growth involved herbaceous crop plants, and information for woody perennial species is very limited (Muthukumar and Udaiyan 2010). ...
We conducted a study to find out if arbuscular mycorrhizal (AM) fungi (Acaulospora scrobiculata, Scutellospora calospora) and phosphate solubilizing bacteria (PSB, Paenibacillus polymyxa) inoculation either individually or in combinations can improve Acacia auriculiformis seedling growth, uptake of nutrients and quality in a phosphorus deficient tropical Alfisol. The seedlings were assessed for various growth and nutrient uptake parameters after 60 days of treatment. Inoculation with P. polymyxa stimulated mycorrhizal formation. Seedling height, stem girth, taproot length, number of leaves and leaf area, plant dry matter production, nodulation, and nodular dry weight were significantly higher for seedlings that were either dual inoculated or triple inoculated compared to individual inoculation of AM fungi or PSB, and uninoculated seedlings. Dual and triple application of AM fungi and PSB also significantly improved the nutrient contents of shoots and roots and nutrient uptake efficiencies. The calculated seedling quality indexes of the AM fungi and PSB inoculated seedling were 25–208% higher than uninoculated seedlings. These findings show that A. auriculiformis seedlings when dual inoculated or triple inoculated performed better than seedlings inoculated with the microbes individually and compared with uninoculated control seedlings. We conclude that bioinoculation is important for the production of high-quality A. auriculiformis seedlings in tree nurseries for planting in nutrient deficient soils.
... De igual modo, los resultados obtenidos indican que los efectos benéficos de los microrganismos pueden tener un papel principal en las diferentes fases vegetativas, como es el proceso de la germinación (Kim y Weber 1985). Resultados similares se han obtenido en otras investigaciones aunque estas han sido en diferentes especies de plantas y otro tipo de bacterias benéficas (Bashan et al., 2009, Rueda et al., 2009, Villegas et al., 2010. ...
The growth-promoting bacteria in plants (BGPB) are a group of different species of bacteria can increase plant growth and productivity. Which can benefit plants through their own bacterial metabolism (phosphate solubilizing, producing hormones or fixing nitrogen). At present, desertification is a growing phenomenon worldwide, afforestation is one of the common solutions to combat this problem. Trees for reforestation are initially grown in greenhouses or nurseries. Among numerous reforestation practices, there is an alternative that inoculation with PGPB. Is a forest species that is endemic Olneya tesota Sonoran Desert, which is in danger of extinction. The objective was to evaluate the effect of bacteria growth promoter in plants with Rhodococcuis fascians and Azospirillum halopraeferens on germination and emergence of Ironwood under four salt concentrations (0, 0.25, 0.5 and 0.75 M NaCl) under greenhouse conditions. Were obtained ironwood seeds in the region of Santa Ana, Sonora. Under greenhouse conditions was evaluated emergence percentage, germination rate, height, plant root length, fresh and dry weight of plant, number of bacterial cells attached to the root system, fresh and dry weight of the root. The results indicate that the germination percentage and other variables evaluated decreased as salinity increases. However, these changed positively to inoculation with bacteria R. fascians and A. halopraeferens.
... PGPB could also widely use to biological control of plant disease and relieve environmental stresses and ensure increased crop yield in agriculture [3]. When associated with plant roots, PGPB actively support plants improvement, health, and resistance against drought and salinity stresses [4][5][6]. PGPB directly or indirectly influence plant growth by fixing N 2 ; solubilizing phosphate; producing siderophores; synthesizing enzymes and various phytohormones, such as indole acetic acid; and reducing ethylene concentration [7][8][9][10]. ...
This paper evaluated the external gelation technique for preparing microcapsules. The microcapsules were consisted of Pseudomonas putida Rs-198 (Rs-198) core and sodium alginate (NaAlg)-bentonite (Bent) shell. Different emulsification rotation speeds and core/shell ratios were used to prepare the microcapsules of each formulation. The near-spherical microcapsules were monodisperse with a mean diameter of 25 μm to 100 μm and wrinkled surfaces. Fourier transform infrared spectrophotometry (FTIR) and thermogravimetric analysis (TGA) revealed the physical mixture of the wall material and the superior thermal stability of the microcapsules. Percentage yield, water content, and encapsulation efficiency were evaluated and correlated with the changes in emulsification rotation speed and core/shell ratio. In vitro release experiments demonstrated that 60% of the bacteria were released from the NaAlg-Bent microcapsules within three days. Considerably better survival was observed for encapsulated cells compared to free cells, especially in pH 4.0 and 10.0. In summary, the desired properties of microcapsules can be obtained by external gelation technique and the microcapsules on the bacteria had a good protective effect.
... De igual modo, los resultados obtenidos indican que los efectos benéficos de los microrganismos pueden tener un papel principal en las diferentes fases vegetativas, como es el proceso de la germinación (Kim y Weber 1985). Resultados similares se han obtenido en otras investigaciones aunque estas han sido en diferentes especies de plantas y otro tipo de bacterias benéficas (Bashan et al., 2009, Rueda et al., 2009, Villegas et al., 2010. ...
The growth-promoting bacteria in plants (BGPB) are a group of different species of bacteria can increase plant growth and productivity. Which can benefit plants through their own bacterial metabolism (phosphate solubilizing, producing hormones or fixing nitrogen). At present, desertification is a growing phenomenon worldwide, afforestation is one of the common solutions to combat this problem. Trees for reforestation are initially grown in greenhouses or nurseries. Among numerous reforestation practices, there is an alternative that inoculation with PGPB. Is a forest species that is endemic Olneya tesota Sonoran Desert, which is in danger of extinction. The objective was to evaluate the effect of bacteria growth promoter in plants with Rhodococcuis fascians and Azospirillum halopraeferens on germination and emergence of Ironwood under four salt concentrations (0, 0.25, 0.5 and 0.75 M NaCl) under greenhouse conditions. Were obtained ironwood seeds in the region of Santa Ana, Sonora. Under greenhouse conditions was evaluated emergence percentage, germination rate, height, plant root length, fresh and dry weight of plant, number of bacterial cells attached to the root system, fresh and dry weight of the root. The results indicate that the germination percentage and other variables evaluated decreased as salinity increases. However, these changed positively to inoculation with bacteria R. fascians and A. halopraeferens.
... Extensive research has resulted in the development of different kinds of free microbial inoculants, but application of microbead alginate formulations to inoculate plants in the soil was done a few times (Bashan, Salazar, and Puente, 2009a;Bashan et al., 2009b;Bashan, Trejo, andde-Bashan, 2011, 2014). ...
The present investigation was carried out to determine the inter-relationship between some physiological attributes of cotton and encapsulated Rs-198 strain. The pot experiment had seven treatments (with or without encapsulated bacteria under different salt stress, 10 replicates) and carried out in the greenhouse during 2014, April to June. Pot results showed that the inoculated encapsulated Rs-198 significantly increased the plant biomass under 0.5% salt stress. Besides, an approximately 19.47% increased in the soluble protein content of cotton with encapsulated Rs-198 inoculated in salt condition and relatively higher chlorophylls a, b and carotenoid concentrations were maintained at 0.626, 0.304, and 0.564 mg/g. Moreover, 42.30% proline content and 24.98% peroxidase activity were reduce when inoculated Rs-198 under 0.5% salt stress. In conclusion, application of encapsulated Rs-198 strain was effective in relieving salt stress under saline conditions. The microcapsules bioinoculants are potential alternatives for sustainable agriculture due to their low cost of production.
... Despite the important economic and agricultural roles played by arboreal crops, little work has been done on the application of PGP bacteria in the field level. Only apple, desert legume and mango trees have been studied (Shishido 1996;Aslantas et al. 2007;Bashan et al. 2009;Bashan et al. 2012;Jaos Frederico et al. 2014). The effects of PGP bacteria on annual crops have also been the focus of research (Bashan et al. 2014 and references therein). ...
Background and AimsLaboratory and greenhouse experiments have shown that root-associated bacteria have beneficial effects on grapevine growth; however, these effects have not been tested in the field. Here, we aimed to demonstrate whether bacteria of different geographical origins derived from different crop plants can colonize grapevine to gain a beneficial outcome for the plant leading to promote growth at the field scale. Methods
To link the ecological functions of bacteria to the promotion of plant growth, we sorted fifteen bacterial strains from a larger isolate collection to study in vitro Plant Growth Promoting (PGP) traits. We analysed the ability of these strains to colonise the root tissues of grapevine and Arabidopsis using green-fluorescent-protein-labelled strain derivatives and a cultivation independent approach. We assessed the ability of two subsets randomly chosen from the 15 selected strains to promote grapevine growth in two field-scale experiments in north and central Italy over two years. Parameters of plant vigour were measured during the vegetative season in de novo grafted vine cuttings and adult productive plants inoculated with the bacterial strains. ResultsBeneficial bacteria rapidly and intimately colonized the rhizoplane and the root system of grapevine. In the field, plants inoculated with bacteria isolated from grapevine roots out-performed untreated plants. In both the tested vineyards, bacteria-promotion effects largely rely in the formation of an extended epigeal system endowed of longer shoots with larger diameters and more nodes than non-inoculated plants. ConclusionsPGP bacteria isolated in the laboratory can be successfully used to promote growth of grapevines in the field. The resulting larger canopy potentially increased the photosynthetic surface of the grapevine, promoting growth.
... Mesquite amargo and the yellow palo verde Parkinsonia microphylla showed positive responses to several of the treatments, while the blue palo verde P. florida did not respond. When these trees were cultivated without water restrictions, inoculation with several growth-promoting micro-organisms induced significant effects on the gas exchange in the leaves, measured as transpiration and diffusive resistance (Bashan et al. 2009a). So far, there have been few attempts to move beyond greenhouse studies and test PGPB in the field. ...
... In the present study, a PGP bacterium P. aeruginosa RRALC3 was isolated from the NRF. Indigenous PGPB are well adapted to native or local conditions though no commercial PGPB products are known to be effective on desert soils [51,52] and the addition of non-indigenous microbes to the soil has the potential to impact the indigenous rhizosphere population [53]. Due to their excellent growth promotion and biocontrol activities P. aeruginosa isolated from the rhizosphere of crop plants and environmental samples can be used as inoculant for promotion of plant growth [54][55][56]. ...
The study was aimed at assessing the effects of indigenous Plant Growth Promoting Bacterium (PGPB) on the legume Pongamia pinnata in the degraded soil of the Nanmangalam Reserve Forest (NRF) under nursery conditions. In total, 160 diazotrophs were isolated from three different nitrogen-free semi-solid media (LGI, Nfb, and JMV). Amongst these isolates, Pseudomonas aeruginosa RRALC3 exhibited the maximum ammonia production and hence was selected for further studies. RRALC3 was found to possess multiple plant growth promoting traits such as nitrogen accumulation (120.6ppm); it yielded a positive amplicon with nifH specific primers, tested positive for Indole Acetic Acid (IAA; 18.3μg/ml) and siderophore production, tested negative for HCN production and was observed to promote solubilization of phosphate, silicate and zinc in the plate assay. The 16S rDNA sequence of RRALC3 exhibited 99% sequence similarity to Pseudomonas aeruginosa JCM5962. Absence of virulence genes and non-hemolytic activity indicated that RRALC3 is unlikely to be a human pathogen. When the effects of RRALC3 on promotion of plant growth was tested in Pongamia pinnata, it was observed that in Pongamia seedlings treated with a combination of RRALC3 and chemical fertilizer, the dry matter increased by 30.75%. Nitrogen, phosphorus and potassium uptake increased by 34.1%, 27.08%, and 31.84%, respectively, when compared to control. Significant enhancement of total sugar, amino acids and organic acids content, by 23.4%, 29.39%, and 26.53% respectively, was seen in the root exudates of P. pinnata. The carbon content appreciated by 4-fold, when fertilized seedlings were treated with RRALC3. From the logistic equation, the rapid C accumulation time of Pongamia was computed as 43 days longer than the control when a combination of native PGPB and inorganic fertilizer was applied. The rapid accumulation time of N, P and K in Pongamia when treated with the same combination as above was 15, 40 and 33 days longer, respectively, as compared to the control.
... Por el contrario, en nuestros resultados la dosis más alta de fertilización (2,3 mM de P en la fertilización 100%) estimuló el crecimiento en altura en los plantines inoculados con PL, por lo que se puede inferir que a las dosis de nutrientes aplicadas los hongos de PL favorecen su asimilación. Bashan et al. (2009), evaluando tres especies de leguminosas, entre ellas Prosopis articulata, inoculadas con HMA, obtuvieron respuestas positivas para altura total, numero de ramas, grosor de tallo, entre otras variables. Estudios realizados por Callejas Ruíz et al. (2009) en Euphorbia pulcherrima, encontraron que la micorrización no mejoró significativamente las variables de crecimiento comparados con los tratamientos fertilizados, atribuyendo esta situación a que ciertos nutrientes limitantes para el crecimiento de las plantas no pudieron ser aportados por las micorrizas. ...
Con el objetivo de evaluar los efectos e interacciones de la aplicación de hongos micorrícicos arbusculares (HMA) y de la fertilización en la producción de plantines de algarrobo blanco, se estableció un ensayo bajo un diseño experimental de parcelas divididas en bloques completos al azar. Los plantines recibieron distintos niveles de fertilización (0%, 25% y 100%) y fueron inoculados con HMA nativos aislados de suelos de algarrobales pertenecientes a Colonia Benítez y Padre Lozano, mientras que el grupo control permaneció no micorrizado. El inóculo de Padre Lozano combinado con la fertilización al 100% produjo los plantines de mayor crecimiento en altura y número de hojas, mientras que el diámetro al cuello fue mayor con 100% de fertilización, tanto con este inóculo como sin inocular.
... Additionally, inoculants must overcome two major problems inherent to living microorganisms: (1) loss of viability during short storage in the grower's warehouse, and (2) long shelf life and stability of the product over a range of −5 to 30°C, within growers' storage conditions. Afzal et al. 2012;Alström 2001;Amein and Weber 2002;Anith et al. 2004;Bacilio et al. 2003Bacilio et al. , 2004Bashan et al. 2006;Boruah and Kumar 2002;Cakmakci et al. 2001Cakmakci et al. , 2006Carrillo-Garcia et al. 2000;Dominguez-Nuñez et al. 2012;Egamberdiyeva 2007;Esitken et al. 2003;Fürnkranz et al. 2012;Guetsky et al. 2002a, b;Guiñazú et al. 2010;Hossain and Mårtensson 2008;Jetiyanon et al. 2003;Khan et al. 2003;Kurek and Jaroszuk-Ściseł 2002;Landa et al. 2001;Lopez et al. 2013;Madhaiyan et al. 2010;Mehnaz et al. 2010;Odee et al. 2002;Ozturk et al. 2003;Puente et al. 2004aPuente et al. , b, 2009aRajapaksha et al. 2011;Singh et al. 2011;Sigler et al. 2001;Sudhakar et al. 2000;Yan et al. 2003;Yu et al. 2011;Zafar et al. 2012 Liquid ( Clayton et al. 2004a, b;Hamaoui et al. 2001;Hungria et al. 2010; Bashan et al. 2002a, b;de-Bashan et al. 2004;de-Bashan et al. 2005de-Bashan et al. , 2008a Regardless of the specific formulation, the nature of the final inoculant can be of four types: liquid, slurry, granular, or powder (Bashan 1998;Catroux et al. 2001). The raw material of the carrier and the type of formulation vary greatly. ...
Background Inoculation of plants to enhance yield of crops and performance of other plants is a century old, proven technology for rhizobia and a newer venue for plant growth-promoting bacteria and other plant symbi-onts. The two main aspects dominating the success of inoculation are the effectiveness of the bacterial isolate and the proper application technology. Scope An assessment of practical aspects of bacterial inoculants for contemporary agriculture and environmental restoration is critically evaluated from the point of view of their current technological status, current applications, and future use. This is done because there are windows of opportunity for new developments in applied research using renewable, non-contaminated natural resources and new venues for research. Special emphasis is given to formulations and polymeric carriers. This review concentrates on practical aspect of inoculation technology dating from 1998 to 2013. Earlier publications are mentioned only for clarification of a specific point. Conclusions This review discusses characteristics of a carrier for inoculants, formulations of inoculants including liquid, organic, inorganic, polymeric, and encapsulated formulations. Technical aspects include inoculation techniques (soil and seed application), mass culture production, bulk sterilization, seed coating, shelf-life, and effect of moisture. Future research venues needed are noted.
... Additionally, inoculants must overcome two major problems inherent to living microorganisms: (1) loss of viability during short storage in the grower's warehouse, and (2) long shelf life and stability of the product over a range of −5 to 30°C, within growers' storage conditions. Afzal et al. 2012;Alström 2001;Amein and Weber 2002;Anith et al. 2004;Bacilio et al. 2003Bacilio et al. , 2004Bashan et al. 2006;Boruah and Kumar 2002;Cakmakci et al. 2001Cakmakci et al. , 2006Carrillo-Garcia et al. 2000;Dominguez-Nuñez et al. 2012;Egamberdiyeva 2007;Esitken et al. 2003;Fürnkranz et al. 2012;Guetsky et al. 2002a, b;Guiñazú et al. 2010;Hossain and Mårtensson 2008;Jetiyanon et al. 2003;Khan et al. 2003;Kurek and Jaroszuk-Ściseł 2002;Landa et al. 2001;Lopez et al. 2013;Madhaiyan et al. 2010;Mehnaz et al. 2010;Odee et al. 2002;Ozturk et al. 2003;Puente et al. 2004aPuente et al. , b, 2009aRajapaksha et al. 2011;Singh et al. 2011;Sigler et al. 2001;Sudhakar et al. 2000;Yan et al. 2003;Yu et al. 2011;Zafar et al. 2012 Liquid ( Clayton et al. 2004a, b;Hamaoui et al. 2001;Hungria et al. 2010; Bashan et al. 2002a, b;de-Bashan et al. 2004;de-Bashan et al. 2005de-Bashan et al. , 2008a Regardless of the specific formulation, the nature of the final inoculant can be of four types: liquid, slurry, granular, or powder (Bashan 1998;Catroux et al. 2001). The raw material of the carrier and the type of formulation vary greatly. ...
Background
Inoculation of plants to enhance yield of crops and performance of other plants is a century old, proven technology for rhizobia and a newer venue for plant growth-promoting bacteria and other plant symbionts. The two main aspects dominating the success of inoculation are the effectiveness of the bacterial isolate and the proper application technology.
Scope
An assessment of practical aspects of bacterial inoculants for contemporary agriculture and environmental restoration is critically evaluated from the point of view of their current technological status, current applications, and future use. This is done because there are windows of opportunity for new developments in applied research using renewable, non-contaminated natural resources and new venues for research. Special emphasis is given to formulations and polymeric carriers. This review concentrates on practical aspect of inoculation technology dating from 1998 to 2013. Earlier publications are mentioned only for clarification of a specific point.
Conclusions
This review discusses characteristics of a carrier for inoculants, formulations of inoculants including liquid, organic, inorganic, polymeric, and encapsulated formulations. Technical aspects include inoculation techniques (soil and seed application), mass culture production, bulk sterilization, seed coating, shelf-life, and effect of moisture. Future research venues needed are noted.
... La sobrevivencia de las tres especies fue de más del 80%, con una sobrevivencia del mezquite de más del 100% después de 10 meses de cultivo. La inoculación con microorganismos promotores de crecimiento ocasionó efectos significativos en el intercambio gaseoso en las hojas de estas plantas, medido como la transpiración y la resistencia a la difusión, cuando estos árboles fueron cultivados sin restricciones de agua (Bashan et al. 2009). Con esta misma combinación de inoculación se realizaron siete ensayos en campo, utilizando adicionalmente cactus cardón. ...
... Researches targeting the development of microbial consortia involving microbial members responsible for nitrogen fixation, phosphorus solubilization, siderophore production, phytohormone synthesis, biological crust formation that would finally support plant growth in symbiotic or non-symbiotic manner could help develop microbe-based strategies for carbon sequestration. Restoration of Sonoran Desert has been demonstrated by bioaugmentation of PGPB formulation consisting of Azospirillum brasilense and Bacillus pumilus, along with arbuscular mycorrhizal fungi and compost 66,67 . However, the plant growth response depends on the varying degrees of bio-formulation application. ...
Desert, comprising one-third of the Earth's surface, was a synonym for 'no life' as it supports very less or no life due to nutritional stress and extreme weather. Microbial autotrophic biochemistry is the principal source of carbon in arid environment, but understanding of these processes in arid ecosystem is limited. Emerging molecular tools have identified associations of phototrophic and chemolithoautotrophic communities often termed as 'biological soil crust' or 'microbiotic crust'. They are the sole sources of carbon and nitrogen, collectively providing soil stability to support vegetation. Here the curiosity arises, whether this phenomenon could be exploited in deserts for carbon sink using microbial community intelligence. By following the precipitation event under regulated nutrient supply that promotes the soil microbial intelligence for autotrophy would enrich soil carbon and nitrogen which in turn support plant growth in desert. Additionally, bioaugmentation of rhizobacteria could enhance the process. This will enable us to refine and formulate our strategies to exploit CO2-fixing microorganisms in such niches vis-à-vis supporting the carbon sink using microbial community intelligence.
Alginate is a polysaccharide with the property of forming hydrogels, which is economic production, zero toxicity, and biocompatibility. In the agro-industry, alginate is used as a super absorbent polymer, coating seeds, fruits, and vegetables and as a carrier of bacteria and fungi as plant-growth promoters and biocontrol. The latter has a high impact on agriculture since the implementation of microorganisms in a polymer matrix improves soil quality; plant nutrition, and is functional as a preventive measure for the appearance of phytopathogenic. Additionally, it minimizes losses of foods due to wrong post-harvest handling. In this review, we provide an overview of physicochemical properties of alginate, some methods for preparation and modification of capsules and coatings, to finally describe its application in agro-industry as a matrix of plant-growth-promoting microorganisms, its effectiveness in cultivation and post-harvest, and its effect on the environment, as well as the prospects for future agro-industrial applications.
Immobilized microorganisms and their use in agriculture as biofertilizers or for biocontrol, is a developing topic; and the concentration of inoculum for bioencapsulation, without affecting the growth and production of metabolites by the microorganism, is an important aspect to consider. Fischerella sp. cells they were encapsulated with calcium alginate using different percentages of inoculum (1, 5, 10 and 20%), and dry weight, NH4 + and phycobiliproteins concentration in biomass were determined. Growth and metabolism of Fischerella sp. was higher in bioencapsulated vs free cells. Dry weight and NH4 + of Fischerella sp. was increased 2.8 times more in bioencapsulated vs free cells. Dry weight value was 0.032 µg mL-1 with the concentration of 20% inoculum, and statistically showed significant differences. Unlike free cells, bioencapsulation protects cells from biotic and abiotic stress, maintaining metabolic activity and viability for longer periods of time. Bioencapsulated from Fischerella sp. to produce NH4 + and its use as a biofertilizer in agriculture, is an alternative versus use of chemical fertilizers.
In present day scenario, the search for an alternative approach to the irrational use of chemical fertilizers has paved the path for the microbial bio-formulations. The employment of PGPR as bio-inoculants impart higher yield of agricultural crops sustaining sustainable ecosystem. Formulations containing bio-inoculants with living microbial cells applied as seed treatments enhance the nutrient mobilization as a cost effective strategy. The problems associated with the microbial inoculants such as economic competitiveness and product development with superior potential of rhizospheric colonization have further necessitated finding new strategies for improving the bio-formulations. In view of this, microbial formulations immobilized on a suitable carrier have gain momentum these days with its wide range of advantages compared to conventional bio-inoculants. The current chapter recapitulates the information pertaining to the various cell immobilized bio-inoculants along with their production and uses in varied fields of technology. The amendments of the immobilized inoculants with the additives functioning as bulking agents improve microbial survival in the matrix. Microbial exo-polysaccharides work as wonder molecules in the immobilization process playing stimulatory effects in the efficacy of a cell immobilized bio-inoculant. The prospective of such inoculant formulations is well elaborated in this chapter by diverse studies focusing on immobilization of PGPR as single inoculants or co-entrapped with other plant beneficial microorganisms. The potential to use innovative technologies to enhance the capacity of bio-inoculants still exists, but ideas must be integrated more effectively and used for sustainable agriculture.
Plant biostimulants are a diverse class of substances obtained from different organic and inorganic substances and from microorganisms. Drought stress has a significant effect on gaseous exchange of plants, which ultimately changes transpiration and photosynthetic and rates and is directly correlated with the yield of agricultural crops. Abiotic stresses responsible for the decrease in crop quality and yield include salt stress, water stress (drought and water logging), extremes of temperature, toxicity of metals, adequate nutrients. Some molecular processes can be modified by the action of biostimulants as it allows to facilitate the efficacy of nutrient and water uptake, stimulates development of plant; and abiotic stresses are tolerated by improving primary and secondary metabolism. Biostimulant applications are vastly utilized in agricultural crops. In agronomic crops, Moringa leaf extract (MLE) was an excellent biostimulator to improve the resistance of the soybean plant against drought stress. In agriculture sector, chitosan (CHT) is recommended as excellent plant growth promoters and green pesticides because of its biodegradation, nonpollution, and nontoxic characteristics. Moreover, a mixture of Pseudomonas species and Bacillus species inoculation in wheat genotypes improved the water deficient tolerance feature. Positive effect of seaweed extract (SWE) on soybean and yeast extract on wheat crop was confirmed by previous studies. In horticultural crops, MLE and CHT improve the physiological characters significantly. SWE product applied on water-deficient trees of citrus rootstocks had remarkably more total growth compared to control (without applied) drought-stressed citrus trees. Under water stress conditions, onion bulb yield was increased due to 9% marine algae extract application. It can be concluded that many biostimulants perform extensively to improve the drought resistance ability of agricultural crops by increasing the growth mechanism of plants.
10.1. Evaluación del potencial biofertilizante de bacterias fijadoras de nitrógeno sobre el cultivo bajo condiciones de invernadero.---
10.2. Caso de estudio de Agrosavia bajo condiciones de campo: inoculante microbiano para reducir la fertilización mineral nitrogenada en la producción de algodón.---
10.3. Caso de estudio de Agrosavia bajo condiciones de invernadero: evaluación del potencial biofertilizante de bacterias solubilizadoras de fosfato sobre el algodón Gossypium hirsutum.
13.1. Uso de rizobios nativos en leguminosas forrajeras como biofertilizantes en el mejoramiento de la producción de ganado de carne en el Valle del Cesar.---
13.2. Inoculación de Vigna unguiculata con cepas nativas de rizobios para evaluar la ganancia en peso de terneros de levante.
Agrosavia, en cumplimiento de su misión de entregar soluciones tecnológicas a los pequeños y medianos productores agropecuarios colombianos, ha desarrollado bioproductos con muy buenos atributos y con potencial para ser usados en el cultivo de tomate, de tal manera que se pueda reducir el impacto negativo causado por las prácticas convencionales y se incrementen tanto la calidad del producto como la competitividad del sector la fertilización edáfica nitrogenada de síntesis química
Los microorganismos del dominio Bacteria son seres vivos cosmopolitas y pueden vivir de manera libre o asociados a otros organismos. Debido a su importancia en los procesos biogeoquímicos, estos representan una pieza esencial de la vida en nuestro planeta.
Hace unas décadas, el uso de fertilizantes de síntesis química se vio como una gran solución para la intensificación de la producción agrícola, pero hoy, debido a sus efectos negativos sobre el medio ambiente y la salud humana, además de sus elevados costos de elaboración, es apremiante la necesidad de encontrar alternativas para la fertilización de los cultivos o, por lo menos, para reducir el uso de los fertilizantes químicos. Por esta razón, muchos investigadores empezaron a centrar sus estudios en una de esas alternativas: la biofertilización; lo han venido haciendo diversas instituciones en todo el mundo, y la Corporación Colombiana de Investigación Agropecuaria (agrosavia), a la cabeza de este proceso en Colombia, no ha sido la excepción.
Es por esto que los profesionales Ruth Rebeca Bonilla Buitrago (agrosavia, Colombia), Luz Estela González de Bashan (Centro de Investigaciones Biológicas del Noroeste, México) y Raúl Osvaldo Pedraza (Universidad Nacional de Tucumán, Argentina), han editado (y escrito) El papel de las bacterias promotoras del crecimiento vegetal en sistemas de agricultura sostenible. Su objetivo es mostrar, basados en su experiencia en diversas investigaciones dentro de la corporación, el papel que estas bacterias pueden desempeñar en la promoción del crecimiento de los cultivos de importancia económica para el país, y lo hacen por medio de quince capítulos.
Tomato (Solanum lycopersicum L.) is an important vegetable cultivated around the world. Under field conditions, tomato can be negatively affected by water scarcity in arid and semiarid regions. The application of native plant growth-promoting rhizobacteria (PGPR) isolated from arid environments has been proposed as an inoculant to mitigate abiotic stresses in plants. In this study, we evaluated rhizobacteria from Cistanthe longiscapa (syn Calandrinia litoralis and Calandrinia longiscapa), a representative native plant of flowering desert (FD) events (Atacama Desert, Chile), to determine their ability to reduce water scarcity stress on tomato seedlings. The isolated bacterial strains were characterized with respect to their PGPR traits, including P solubilization, 1-aminocyclopropane-1-carboxylate deaminase activity, and tryptophan-induced auxin and exopolysaccharide production. Three PGPR consortia were formulated with isolated Bacillus strains and then applied to tomato seeds, and then, the seedlings were exposed to different levels of water limitations. In general, tomato seeds and seedlings inoculated with the PGPR consortia presented significantly (P ≤ 0.05) greater plant growth (48 to 60 cm of height and 171 to 214 g of weight) and recovery rates (88 to 100%) compared with those without inoculation (37 to 51 cm of height; 146 to 197 g of fresh weight; 54 to 92% of recovery) after exposure to a lack of irrigation over different time intervals (24, 72 and 120 h) before transplantation. Our results revealed the effectiveness of the formulated PGPR consortia from FD to improve the performance of inoculated seeds and seedlings subjected to water scarcity; thus, the use of these consortia can represent an alternative approach for farmers facing drought events and water scarcity associated with climate change in semiarid and arid regions worldwide.
Indian livestock sector is one of the largest in the world and fodder is vital component of profitable animal production. Legumes are one of the predominant crops of mixed crop-livestock systems providing highly nutritious fodder as well as contributing soil fertility. Nevertheless, the fodder production and quality in the country is not adequate to meet out the prerequisite of growing livestock population. Optimum nutrition is thus required for getting the maximum forage yield and quality. Nutrient Management is propounded as a promising strategy for addressing such challenges. Microbial inoculants being an important component of integrated nutrient management are eco-friendly and economical sources of nutrient. The benefit of combining organic and inorganic sources of nutrients in integrated nutrient management has proved superior to the use of each component individually. Thus, the present review will feature the need of integrated nutrient management, plant growth promoting rhizobacteria as microbial inoculants, role of microbial inoculants in integrated nutrient management of various leguminous crops and emerging examples of integrated nutrient management in cowpea. The realization attained from literature assessed herein will further help to understand the role of microbial inoculants in integrated nutrient management.
Aims: Desertification is a major concern in arid and semi-arid regions globally. Understanding interactions between vulnerable plant species and associated microbial symbionts may have important applications for conservation and restoration strategies in affected areas. Methods: In this study, we evaluated the root-associated fungal endophyte community in Prosopis chilensis, a vulnerable and threatened arid-adapted tree of northern Chile. Host benefits in terms of physiological performance and plant growth were also assessed. Endophytic fungi were isolated from asymptomatic roots by the culture method for molecular identification of the 18S rRNA gene. The dominant fungal endophyte (Penicillium sp.) in the community was later used in inoculation experiments to assess its effect on maximum quantum efficiency of photosystem II (PSII), (Fv/Fm) actual PSII efficiency (Φ PSII ), and non-photochemical quenching (NPQ). Total sugars, starch content, malonaldehyde (MDA), nitrogen content (%) and growth traits were also measured. Important Findings: Whereas Φ PSII increased significantly in endophyte-inoculated plants, NPQ was found to decrease. No effect of endophyte inoculation on sugars and MDA was detected, but starch content, leaf nitrogen content, number of leaves and shoot biomass were found to increase. Results revealed that inoculation of endophytic Penicillium fungal isolate can provide significant physiological benefits to the host plant P. chilensis. Its presence resulted in greater PSII efficiency and higher leaf nitrogen and carbohydrate content, enhancing host plant growth. These findings highlight the importance of considering the fungal endophyte community of this vulnerable species as an important tool to the design of further revegetation and conservation programs.
INTRODUCCIÓN La ganadería y la agricultura ocupan un importante renglón en la economía del departamento del Cesar (Viloria, 2003); debido a esto es necesario producir forrajes de buena calidad que contribuyan a la alimentación y nutrición del ganado; sin embargo, el suelo de esta región presenta de forma natural la tendencia a la pérdida de la materia orgánica, déficit hídrico, bajos niveles de nitrógeno y sus propiedades físicas han sido alteradas por prácticas de manejo inadecuadas tanto agrícolas como ganaderas (Mosquera, 1984; Valero, et al., 2010). En ese sentido se hace necesario desarrollar alternativas ecológicas que posibiliten la recuperación y conservación de las condiciones del suelo, y que puedan aplicarse para mejorar la calidad de las plantas para la producción de forrajes. Bajo este contexto se ha propuesto que una medida pertinente es utilizar enmiendas que permitan mejorar el contenido de materia orgánica y los nutrientes del suelo (Bashan, 2005). En el suelo resulta muy importante la actividad de los microorganismos benéficos asociados a la rizósfera de las plantas; como es ampliamente conocido, las bacterias promotoras del crecimiento vegetal (BPCV) pueden actuar de forma benéfica sobre las plantas proporcionando a la planta factores de crecimiento de naturaleza hormonal y nutricional (fijación de nitrógeno atmosférico, solubilización de fosfatos) y protegiendo a las plantas de microorganismos fitopatogenos (Bashan y de-Bashan, 2005). Por ésta razón se ha estudiado extensamente la aplicación de inoculantes biológicos obtenidos a partir de bacterias promotoras de crecimiento vegetal en forma de fertilizantes biológicos para la agricultura, de tal forma que en el mercado se encuentra variedad de productos elaborados a base de diferentes hongos y bacterias altamente eficientes. Pero a pesar la cantidad de productos biofertilizantes que se comercializan las experiencias de su utilización a menudo presentan inconsistencias en los resultados en campo, al respecto se ha recomendado el uso de microorganismos nativos para la elaboración de bioinsumos para la aplicación local (Valero, 2007) Por otra parte, en la minería de carbón a cielo abierto se generan diferentes tipos de carbón, los carbones de mayor grado evolutivo (carbones de alto rango) como la antracita son los
Bacteria (Pseudomonas sp. and Bacillus sp.) and/or the arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices were able to improve growth, physiological and biochemical characteristics of four Sulla carnosa Desf. provenances (Sidi khlif, Thelja, Kalbia and Kerker) from Tunisia under both saline and non-saline conditions. S. carnosa is a salt-tolerant legume plant, native from North Africa. The intrinsic bacterial characteristics evidenced the fitness of these bacteria to support salt stress and to stimulate plant growth. Bacillus sp. produced more indol acetic acid (IAA) than Pseudomonas sp. and showed a great surviving capacity under salt conditions supporting its capacity to improve plant growth under stress conditions. The microorganisms applied also have a different potential to increase the nutritional and related plant growth parameters. It is noticeable that some provenances reached the highest level of growth when inoculated with Bacillus sp. in Sidi khlif or by Bacillus plus AMF in Kalbia, which increased shoot by 318% and root by 774%. In contrast, in Thelja and Kerker the impact of the test microorganisms was mainly evidenced at increasing nutritional and physiological functions. Salinity reduced some growth and physiological variables as stomatal conductance, photosynthetic pigments and photosynthetic efficiency and increased electrolyte leakage. However, the microbial inoculants compensated these detrimental effects in a degree depending on the S. carnosa provenance. These microorganisms also orchestrate antioxidant activities involved in adaptative responses in S. carnosa provenances. The intrinsic ability of inoculants allow us to select the provenance/microorganism combination which maximizes S. carnosa growth, nutrition and physiological/biochemical responses under salt and non-salt conditions. The results obtained support that the target microbial inocula are beneficial for the ecological stability if this Mediterranean legume.
The establishment of the arbuscular mycorrhizal (AM) fungus in the root cortex is known to change many key aspects of plant physiology and the mineral nutrient composition in plant tissues, the hormonal balance and the patterns of C allocation. Consequently, AM colonisation induced many plant changes which affect the microbial populations, both quantitatively and qualitatively, in either the rhizosphere or the rhizoplane. However, there are specific modifications in the environment surrounding of the AM extraradical mycelium itself. Thus, the mycorrhizosphere formed around AM plants has features that differ from the rhizosphere of a nonmycorrhizal plant. Bacteria living in the soil root surface or inside cortical cells can interact with AM fungi. The cooperative plant–microbial interactions have focused their attention on plant growth-promoting bacteria (PGPB) and AM fungi and processes involved in the establishment and functioning of the mycorrhizosphere. AM and PGRB inoculation improved plant performance at low levels of nutrients, water potential, at high amount of heavy metals and under diseases caused by pathogenic associations. All the detrimental effects in plants of these stresses can be compensated by specific microbial associations in the mycorrhizosphere based on a range of physiological and cellular mechanisms here reported.
Background
Azospirillum spp. are the most studied plant growth-promoting bacteria (PGPB). The genus represents a common model for plant-bacteria interactions. This genus was initially isolated and tested on cereals and was subsequently commercialized.
Aims
Despite claims of plant specificity, particularly towards cereals, data over the past 40 years does not appear to substantiate claims of such specificity/affinity of Azospirillum species. Consequently an evaluation of the specificity/affinity of the genus Azospirillum across all plants, in general, and cereals, in particular, was undertaken.
Results
Although the majority of studies focused on cereals, Azospirillum spp. increase growth of 113 plant species across 35 botanical families, including 14 species of cereals. Amongst Azospirillum spp., several well studied strains have been effective in several plant species, making these organisms potentially valuable for further study.
Conclusions
This review demonstrates that azospirilla are not cereal-specific at the genus and species levels. Azospirillum serves as a general PGPB to every plant species tested so far. Given the paucity of widespread screening, affinity of strains to a plant genotype, cultivar, or plant species cannot be overruled. Definitive conclusions concerning such specificity require molecular and cross-inoculation studies, using various strains of bacteria, and re-isolation after growth of the plants in different plant species. (203 words).
Kelp residue is the main waste of kelp processing. Kelp residue solid fermentation inoculated with one Bacillus subtilis strains JGA2 (-5) 27-2 was studied through this research. Inhibitory activity against Aspergillus parasiticus and the production of plant hormones 6-furfurylaminopurine under different fermentation conditions were measured. Single factor experiment and response surface methodology were done to optimize the fermentation conditions. Results showed that sucrose and nitrates were the optimal carbon source and the optimal nitrogen source, respectively. Optimal incubation sucrose concentration, potassium nitrate concentration, incubation time, moisture content, incubation temperature, inoculation amount, and pH were 2.091%, 0.507%, 8.24 days, 60%, 35℃ and 4%, and natural, respectively. K+ ion was introduced into microbial fertilizer in the form of KNO3 as plus nitrogen. The research not only shown that to produce microbial fertilizer by using kelp residue solid was also feasible, but also provided reference for kelp residue resource utilization in the field of agriculture.
Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that aggressively colonize plant roots and enhance plant growth by a wide variety of mechanisms such as phosphate solubilization, phytohormone production, antifungal activity, etc. In this study, effect of plant growth promoting rhizobacteria (PGPR) on Piper nigra was examined. Azotobacter species, Nitrobacter species, and Nitrosomonas species were isolated and identified using standard methods. In-vitro screening of these PGPR was carried out to test their ability to produce phytohormones (siderophore, phosphate solubilization and indole acetic acid). Seed germination and seedling growth test were also conducted to evaluate the effect of PGPR on the germination of Piper nigra seeds. The growth parameters (plant height, stem width root length and the internode of the plant) were monitored at 5 days after planting (DAP) interval from the day of sprouting. The findings of the study showed that the ability to solubilize phosphate was exhibited by Nitrobacter species and Nitrosomonas species while Azotobacter species produce indole acetic acid (IAA) and siderphore. It also showed that the combined use of the three isolates gave the best performance in terms of enhanced increases in growth parameters than the control (treatment A). Thus, the use of combined biofertilizers is advocated for excellent growth performance of plants.
Plants are limited to protect themselves against environmental stresses including drought. Thus, plants develop a wide range of strategies to cope with stress situations. Under conditions of water deficiency, drought escape and drought tolerance are two important strategies to ensure plant growth. There is limited reported information dealing with the role of microbes on the improvement of drought tolerance. Here, we provide an overview of current knowledge on the general features of the induction of drought tolerance mediated by inoculation of plants with fungi, bacteria, and viruses, and several bacterial determinants and plant signaling transduction pathways revealed by classic physiological or morphological observations and recent “Omics” technology. Overall, the application of microbes provides new insights into novel protocols to improve plant defense responses to drought, an important component of agricultural production systems affected by a changing climate.
Deforestation in the tropics often leads to unproductive agriculture and results in abandoned, degraded grasslands that tree species recolonize poorly. To evaluate why forests do not regenerate naturally and to identify potential species for use in reforestation of degraded areas, we planted 15 000 seeds of 20 native tree species, varying in seed size and shade tolerance, in abandoned Panamanian farmland dominated by the exotic grass, Saccharum spontaneum . To determine the effects of above- and belowground constraints on tree seedling germination, survival, and growth, we used four mowing and shading treatments of the Saccharum. Shading the Saccharum effectively eliminated it, whereas mowing led to increased light aboveground, but did not reduce Saccharum growth rate. Germination, survival, and growth of tree seedlings approximately doubled in shade treat- ments compared to the unshaded control, but were lowest when the Saccharum was mowed three times. Fire significantly decreased germination and survival. Some species did not follow these general trends, however; we identified four species groups that varied in their response to Saccharum competition. Very small-seeded, light- demanding species performed poorly, and we do not recommend their use in reforestation because they tolerate neither above- nor belowground constraints imposed by the Sac- charum. Light-demanding species with large seeds were limited by aboveground constraints, namely, shading. Small-seeded, shade-tolerant species were limited by belowground con- straints imposed by the Saccharum. Large-seeded, moderately to highly shade-tolerant species performed well in the Saccharum; we recommend a reforestation strategy that includes planting this last group.
Summary Sand culture pot experiments were carried out with Proposis seedlings in the greenhouse on a nitrogen free nutrient solution with increasing levels of sodium chloride. All species tolerated a 6,000 mg/l salinity with no reduction in growth.P. velutina was the only species that poorly tolerated the 12,000 mg/l salinity level.P. articulata, P. pallida, andP. tamarugo tolerated 18,000 mg/l NaCl with little reduction in growth and grew slightly in a salinity (36,000 mg/l NaCl) greater than seawater. This is the first legume known to grown in salinities equivalent to seawater.
Recovery from water stress was studied on similarly sized VA mycorrhizal and non-mycorrhizal rough lemon seedlings (Citrus jambhiri Lush). VA mycorrhiza affected stomatal conductance, photosynthesis and proline accumulation, but not leaf water potential, suggesting that most of the effect of the mycorrhizal association is on stomatal regulation rather than on root resistance.
We found that the most effective and economical method for establishing native shrubs on extensive areas of retired cropland in southern Arizona makes use of drip irrigation and 3.8-l (1-gal) transplants (outplants). In March 2001, we established a small (8 ha [20 ac]) field trial to test the effectiveness of different combinations of transplanting, seeding, drip irrigation, and furrow irrigation. Treatments utilizing transplants and drip irrigation had higher survival and lower densities of weed species than other treatments tested. Based on these results, we planted again in November 2001 using drip-irrigated transplants to examine the effectiveness of this method over a larger scale (85 ha [210 ac]). As a further refinement of this method, we tested various sizes of container stock and determined that transplants of 3.8-l (1-gal) size had superior growth and survival when compared to smaller-sized transplants. The total cost of this method is approximately US$ 4430/ha ($1790/ac), but it is more likely to succeed as compared with direct seedings, which is a commonly used approach to revegetation in southwestern ecosystems. Although a drastic effort, our technique holds promise for revegetating environments in the hottest and driest parts of the Sonoran Desert in southern Arizona.
Azospirillum cells were inoculated in pregerminating wheat during seed imbibition. Surface-sterilized seeds of Triticum aestivum cv. Buck Pucara were sequentially soaked for 3 h in water and 3 h in the inoculum of 3 x lo8 Azospirillum brasilense Sp 245 cells. rnL-I, to allow bacteria to enter during imbibition. Germination and seedling growth were accomplished in sterile distilled water at 20°C, in the dark. To compare with more traditional methods based on plant- Azospirillum colonization after germination, seedlings from noninoculated seeds were inoculated in parallel by immersing roots in the same inoculum, for the same period of time. Autoclaved inocula were used as controls in all cases. We observed about 5 x lo8 Azospirillum cells. g-I fresh weight in 11-day-old wheat seedlings inoculated before or after seed germination. However, roots from seed-inoculated seedlings had higher both bacterial concentration and length. On the other hand, seeds inoculated during imbibition and dried to 14% water content retained 3.7 x lo6 viable cells. g-l dry weight up to 27 days. Moreover, seeds stored for 30 days were not only able to germinate but also to harbor over lo6 cells. g-I fresh weight in roots after 7 days growth. Here we present the possibility of obtaining in a simple and inexpensive way, seeds containing high numbers of viable Azospirillum cells, which could avoid the use of external carriers or adhesives.
A local species of oak (Quercus ilex ssp. ballota) was inoculated or co-inoculated with the ectomycorrhizal fungus Pisolithus tinctorius and two plant growth promoting rhizobacteria (PGPR) of the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105). Effects of inoculation on growth, on N acquisition by the plant roots, changes in rhizosphere microbial communities and the degree of mycorrhization were evaluated. Only B. licheniformis promoted the growth of Q. ilex seedlings while co-inoculation of either bacterial strain with P. tinctorius had a negative effect on plant growth. Furthermore, B. licheniformis inhibited fungal growth as revealed by ergosterol/chitin analysis. As shown by phospholipid fatty acid profiles, the inoculation caused a slight alteration in the microbial community structure of the rhizosphere, both in the total community and the culturable populations.
Although not a panacea, management of mycorrhizae and associated organisms is an important reforestation aid. Its three major components are protection of the indigenous soil community and evaluation of inoculation needs, integration of inoculation programs into existing reforestation technology, and research. Clear-cutting frequently results in reduced mycorrhizae formation, particularly when reforestation is delayed and no other host plants are present to maintain fungal populations. Implications of such reductions for reforestation vary with environmental factors and tree species. Adequate mycorrhiza formation is especially critical for ectomycorrhizal trees growing on poor soils or in environments where seedlings must establish quickly to survive. It may also be important where early successional, noncrop plants do not support the same mycobiont as the crop. In such circumstances, a self-reinforcing trend may develop, with poor mycorrhiza formation reducing seedling survival and poor tree stocking leading to further loss of mycorrhizal inocula. Inoculating nursery seedlings with mycobionts holds promise for improving outplanting performance only if site-adapted fungi are used. A practical alternative is to improve nursery practices to enhance natural populations of mycorrhizal fungi. Seedlings leaving the nursery with diverse mycorrhizae may perform better than those leaving with only one or a few nursery-adapted types. Research is needed in three broad areas: on adaptations of mycorrhizal fungi to particular environmental factors; on interactions between tree seedlings and processes occurring within the sphere of influence of roots (the rhizosphere) or of mycorrhizal roots (the mycorrhizosphere); and on the role of mycorrhizae and associated organisms in ecosystem structure and processes, particularly nutrient cycling, plant-plant interaction, and soil structure.
Leguminous trees were examined for use on hot/arid lands in field trials in the California Imperial Valley where July daily maximum temperatures are 42°C (108°F). Two field trials were carried out to rank 55 accessions in biomass per tree and to evaluate biomass production per unit area with four of the more productive accessions identified in earlier trials. The trial with 55 accessions compared Prosopis (mesquite) to widely recommended species for arid lands such as Leucaena leucocephala (K-8), Parkinsonia aculeata, and Prosopis tamarugo and to other drought adapted tree legume species of California/Arizona deserts such as Cercidium floridium and Olneya tesota. Prosopis selections were identified that had greater productivity than either Leucaena leucocephala (K-8) or Parkinsonia aculeata. The mean ovendry biomass per accession ranged from 0.2 kg/tree for Prosopis tamarugo to 29 kg/tree for P. alba (0166) when measured 2 years from germination in the greenhouse. Clones were obtained from trees in this trial which had 45-56 kg/tree (ovendry) in two seasons. The plots designed to measure biomass production per unit area were on a 1.5 m spacing and had productivities of 7, 11.2, 14.3, and 14.5 ovendry T ha-1 yr-1 for P. glandulosa var torreyana (0001), P. alba (0163), P. chilensis (0009), and P. alba (0039), respectively, when measured 2 years from germination in the greenhouse. Forest Sci. 29:592-606.
BOWERS, J. E. AND R. M. TURNER. (U. S. Geological Survey, Tucson, AZ 85745). Dieback and episodic mortality of Cercidium microphyllum (foothill paloverde), a dominant Sonoran Desert tree. J. Torrey Bet, Sec. 128:000-000. 2001. - Past and current dieback of Cercidium microphyllum a dominant, drought-deciduous tree in the Sonoran Desert, was investigated at Tumamoc Hill. Tucson, Arizona, USA. Logistic regression predicted that the odds of a Ceracidium plant being alive should decrease with increasing circumference, association with the columnar cactus Carnegiea gigantea, and occurrence on steep slopes. Slope azimuth. parasitization by Phoradendron californicum, and distance to nearest Ceracidium within 5 m did not significantly affect the odds of survival. Ceracidium was a source of background mortality rather than a primary cause of dieback. Of the >1,000 living and dead plants sampled, 7.7% had died within the past 5 to 7 years. An additional 12.8% died in the more distant past. Diebacks tended to occur during severe deficits in annual, especially summer, min. More than half of the dead plants in the sample were greater than or equal to 50 cm in girth. In current and past diebacks on Tumamoc Hill, it seems likely that severe drought interacted with natural senescence of an aging population. weakening large, old trees and hastening their deaths.
Ecological devastation is becoming a serious problem locally to globally, inproportion as people seek affluent living circumstances. Environmental devastation originated mainly from nature exploitation and construction of cities and industrial institutions with non-biological materials. Humans have ignored the rules of nature, biodiversity and coexistence.One of the best measures we can take anywhere, in order to restore ecosystems indigenous to each region and to maintain global environments, including disaster prevention and CO2 absorption, is to restore native, multi-stratal forests following an ecological method.I would like to refer to the experimental reforestation projects based on ecological studies and their results at about 550 locations throughout Japan and in Southeast Asia, South America, and China. We have proved that it is possible to restore quasi-natural multi-stratal forest ecosystems in 20 to 30 years if we take the ecological method.
(1) Leaf diffusive resistance was determined for young potted Sitka spruce seedlings grow under controlled conditions in a wind tunnel. (2) Changes in windspeed (0.1 m s-1-4 m s-1) had no effect on transpiration rate, since changes in the boundary layer resistance were balanced by changes in diffusive resistance, apparently brought about by partial stomatal closure. (3) Changes in leaf diffusive resistance in response to vapour pressure deficit (2-11 mb) implied progressive stomatal closure. Stomata were normally open in the dark at low v.p.d. (4) Increases in v.p.d. resulted in reduced height growth which was shown to be equivalent to the calculated reduction in diffusivity of CO2. (5) The implications for performance in the field are briefly discussed.
A local species of oak (Quercus ilex ssp. ballota) was inoculated or co-inoculated with the ectomycorrhizal fungus Pisolithus tinctorius and two plant growth promoting rhizobacteria (PGPR) of the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105). Effects of inoculation on growth, on N acquisition by the plant roots, changes in rhizosphere microbial communities and the degree of mycorrhization were evaluated. Only B. licheniformis promoted the growth of Q. ilex seedlings while co-inoculation of either bacterial strain with P. tinctorius had a negative effect on plant growth. Furthermore, B. licheniformis inhibited fungal growth as revealed by ergosterol/chitin analysis. As shown by phospholipid fatty acid profiles, the inoculation caused a slight alteration in the microbial community structure of the rhizosphere, both in the total community and the culturable populations.
Biomass components of mesquite (Prosopis juliflora(Swartz)DC) and palo verde (Cercidium floridum (Benth)) soil-plant systems were collected during spring, winter, and fall for 3 years to study the temporal distribution of the mass of understory vegetation and litter and the dynamics of nitrogen and carbon in all biomass components. Mass of palo verde litter changed seasonally while that of mesquite did not change. With exception of mesquite litter, mass of understory vegetation and litter did not change annually for either shrub. Seasonal and annual changes were observed in both N and C of selected shrub, understory, and litter components, but these changes were more prevalent in mesquite than palo verde. Seasonal changes appeared primarily related to N and C demand in regions of rapid growth. Annual changes appear related to weather phenomena which regulate decomposition, uptake, and growth.
Resource-island soils formed by some plants in arid lands are capable of supporting certain plants that do not normally establish in surrounding areas free of vegetation. We determined growth responses of Pachycereus pringlei (cardon), the giant columnar cactus, whose widespread, finely branched, subsurface root systems stabilize desert soils, to four soils collected from within or outside of resource islands. Traits of cardon grown in soils from mature (MM) or young (YM) Prosopis articulata (mesquite), mature Olnea testosa (ironwood, MI), or bare areas (BA) were compared, to determine differences between the effects of soils due to the identity or the stage of development of nurse plants. The levels of soil N, P, and C contents were in the order MM> > YM > MI BA. The BA soil had the coarsest and MM soil the finest texture. Cardon was also grown in pot cultures inoculated with the plant-growth-promoting bacterium Azospirillum brasilense, or in association with a competing grass, Sorghum bicolor (sorghum). Competition did not affect survival rates of cardon in any of the soils after six months of growth, but decreased biomass accumulation by up to 90% in the best (MM) soil. Inoculation of cardon seeds with A. brasilense did not affect survival but resulted in significantly better root and shoot growth, and this effect increased linearly as soil nutrients declined. In the best soil (MM), A. brasilense had no effect on cardon growth, but in the poorest soil (BA) shoot dry mass was almost 60% and root length over 100% greater as a result of inoculation, with responses in the other two soils intermediate. This effect did not appear to be owing to N2 fixation, as nitrogenase activity (acetylene reduction) was not detected in any of the treatments. Soil formation by selected nurse trees in arid areas is an important factor in plant establishment and growth, and the present results indicate that these processes can be impeded or facilitated by the introduction of competing or beneficial organisms. The use of beneficial microorganisms associated with roots may accelerate the restoration of disturbed areas.
Key words: Azospirillum, desert soils, nitrogen fixation, nurse plant, Pachycereus pringlei, plant survival, resource-island.
Four bacterial strains showing in vitro metabolic capacities related to their plant growth-promoting action (plant growth-promoting rhizobacteria (PGPRs)) were studied in the growth of holm-oak (Quercus ilex ssp. Ballota) and pine (Pinus pinea) plants at a forest nursery before outplanting. All strains significantly increased some of the parameters studied (stem length, neck diameter and shoot dry weight), although, neck root diameter showed the smallest increase in general. An interaction plant/bacterial strain was observed. Some strains specifically increased aerial parameters in both plant species, whereas other strains did so mainly in one plant species. Analyses of PLFAs and incorporation of thymidine and leucine suggest differences in the perturbation of microbial communities previously established and in the capacity of adaptation to the rhizosphere environment among the different strains.
Wild Cardon cactus seeds were inoculated with Azospirillum brasilense strains Cd and Sp-245 to improve seed germination and seedling growth parame- ters. Differential germination responses were related to the bacterial strain. A. brasilense Cd (the type strain for the species A. brasilense) significantly decreased seed germination. A. brasilense Sp245 (a known beneficial bacteria for cereal plants) significantly increased the germination of the seedlings at the same inoculum concentration. Both bacterial strains improved several plant growth parameters related to seedling survivability (height, diameter, volume and the volume/surface ratio) and decreased the aging process of the seedling spines. Both strains of A. brasilense survived in the cactus rhizosphere for about 300 days after seed inoculation. This study adds further evidence that A. brasilense should be considered as a non-specific beneficial bacteria and we propose the inoculation of Cardon cactus seeds as a possible means of enhancing seedling growth in nurseries.
Augé, R. M. 2004. Arbuscular mycorrhizae and soil/plant water relations. Can. J. Soil Sci. 84: 373-381. The water relations of arbuscular mycorrhizal (AM) plants have been compared often. However, virtually nothing is known about the comparative water relations of AM and nonAM soils or about the relative influence of AM colonization of soil vs. AM colonization of plants on host water balance. In this review, I summarize findings that support the assertion that colonization of soil may play as impor- tant a role as colonization of roots regarding how AM symbiosis affects the water relations of host plants. We observed a slight but significant AM effect on the soil moisture characteristic curve of a Sequatchie fine sandy loam following 7 mo of mycor- rhization by Glomus intraradices/Vigna unguiculata. In a separate study, few AM effects on either the wet or dry hysteretic curves were discernible after 12 mo of mycorrhization by G. intraradices or Gigaspora margarita on roots of Phaseolus vulgaris. Using myc- bean mutants, we determined that about half of the considerable promotion of stomatal conductance by G. intraradices and Gi. margarita was attributable to soil colonization and about half to plant colonization. A path analysis modeling approach revealed that soil hyphal colonization had larger direct and total effects on dehydration tolerance of bean than did root hyphal col- onization or several other soil or plant variables.
Perennial plants of 19 families were surveyed for colonization by vesicular-arbuscular mycorrhizal (VAM) fungi in the Anza-Borrego Desert State Park, an area characterized as arid to extremely arid. Soils at all sites were very low in P and N and had a coarse sandy texture. All plants (38 species) were colonized by VAM fungi (6 species). Site preference by VAM-fungal species was ascribed to an interaction of factors pertaining to the host plants and to edaphic and climatic conditions. -from Authors
Immobilization of Bacillus pumilus ES4 from arid land soils, a plant growth-promoting bacterium and the freshwater, green microalga Chlorella vulgaris enhanced microalgal growth only in the absence of combined nitrogen in synthetic growth medium (SGM), but not in medium with combined nitrogen. B. pumilus was able to fix nitrogen in N-free SGM and its growth yielded an accumulation of ammonium in the medium. On its own, B. pumilus is a poor agent for removing nitrogen and phosphorus from wastewater, while C. vulgaris is a capable microorganism. By jointly immobilizing the two microorganisms, the capacity to remove nitrogen and phosphorus from the medium by the microalgae culture was not enhanced, but, at the cell level, removal of these nutrients was significantly enhanced. It appears that growth promotion induced by B. pumilus on C. vulgaris is related to nitrogen fixation.
Survival and development of cactus transplants in urban, disturbed areas of the desert near La Paz, Baja California Sur, Mexico, was monitored. Young plants of three species of pachycereid cacti (Pachycereus pringlei, Stenocereus thurberi, and Lophocereus schottii) inoculated with the plant growth promoting bacterium Azospirillum brasilense in an eroded area (a dirt road) had a high survival rate and developed more rapidly compared with uninoculated control plants during a 3.5-year period after transplantation. Soil erosion in the inoculated experimental area diminished. Small, but significant soil accumulated in association with the growth of cactus roots into the wind-deposited dust. One demonstrated mechanism for stabilizing dust was by the upward growth of small roots during the rainy season into the deposited dust. Azospirillum brasilense survived well in the rhizospheres of these cacti for 2 years, but not in root-free soil. This study demonstrated the feasibility of using bacterial inoculation of cacti to enhance their establishment in disturbed areas, with the potential to stabilize soil.
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Seedling root systems are colonized heavily by asymbiotic soil bacteria, many of which have the potential to influence plant growth significantly. A heterogeneous group of these microorganisms is well known for their ability to colonize roots and stimulate growth of agricultural plant species, sometimes doubling seedling biomass accumulation only a few weeks after inoculation, but more usually resulting in less spectacular biomass gains (e.g., 15%-30% greater than uninoculated controls within a growing season). Plant growth promoting soil bacteria may exert such effects through a variety of mechanisms, and include microorganisms that stimulate seedling emergence or infection by symbiotic fungi and bacteria. Other plant beneficial soil bacteria possess biological control activity or are capable of transforming plants genetically. Inoculation of tree seedlings with such bacteria before outplanting would be an inexpensive, environmentally benign, and easily applied nursery treatment, but comparatively little work has been performed with these microorganisms in forestry. Recent results with various tree species, however, indicate that seedling performance can be significantly enhanced through bacterial inoculation of root systems: pine and spruce biomass increased 32%-49% 1 yr after inoculation and outplanting at a reforestation site. In addition, infection by desired species of ectomycorrhizal fungi can also be enhanced by inoculation with certain strains of root colonizing bacteria. Results from studies performed with beneficial asymbiotic tree root associated bacteria are reviewed in this article in relation to the possible uses of such microorganisms for artificial forest regeneration. For. Sci 43(1):99-112.
Loblolly (Pinus taeda L.), slash (Pinus elliottii Engelm.), and longleaf pine (Pinus palustris Mill.) seeds were inoculated in the greenhouse with rhizobacteria recovered from 4-month-old bareroot loblolly pine seedlings. Emergence and seedling densities were determined at 3- and 8-week intervals after sowing, respectively, with root and shoot biomass measured at 12 weeks. All bacterial strains significantly increased the speed of seedling emergence relative to untreated loblolly and slash pine seeds, while five strains significantly slowed longleaf germination. For loblolly and slash pine, there were no differences in percentage germination when comparing treated and untreated seed. However, all bacterial strains significantly reduced longleaf germination over nontreated seed. Treatment with rhizobacteria had significant positive and negative effects on seedling growth and biomass, depending on the tree species and bacteria isolate used. Five of the eight bacterial isolates tested increased shoot length of loblolly pine seedlings, whereas one strain increased above- and belowground biomass. Slash pine seedlings experienced growth increases with three bacterial strains. However, two bacterial strains, ALA-41G and ALA-54G, resulted in shorter slash pine shoots. Only strain ALA-3G increased shoot biomass of longleaf pine over nontreated longleaf seed. Increased seedling emergence and growth promotion by rhizobacteria collected from Pinus sp. is a potential useful tool for management of these forest species. The effect may be species-specific and the use of bacteria in forest nurseries for growth promotion will need to take this into account. FOR. SCI. 51(6):541–545.
Root growth was monitored in hydroponic systems under greenhouse conditions. Inoculation with Azospirillum brasilense increased the total number and length of adventitious roots of Sorghum bicolor by 33–40% over non‐inoculated controls. This resulted from a higher rate of growth, earlier root appearance and a greater elongation rate of individual sorghum roots. Inoculation also led to a 25–40% increase in hydraulic conductivity of the inoculated root system as compared to controls. In plants subjected to an osmotic stress by the addition of polyethylene glycol (PEG 6000) to the growth medium to produce an osmotic potential of ‐2.0 bar, inoculation significantly diminished most of the drastic adverse effects on root growth. It was concluded that beneficial effects of Azospirillum on the growth and yield of sorghum can be attributed largely to improved growth and function of the root system.
To date, the principal constraint upon the implementation of a dust monitoring programme for desertification control in West Africa, is our limited knowledge of the dust processes to be monitored. A review of the state of dust research in Africa and over the Atlantic reveals a strong imbalance in favour of the latter, and resolves some misconceptions concerning dust source-areas and the relative importance of winter and summer dust. The results of Atlantic Ocean dust research are here brought together with the recent results of Harmattan dust research in Nigeria to demonstrate, at least tentatively, that the Harmattan and winter dust comprise a contiguous aeolian process system referred to as the Harmattan aeolian system.
The Harmattan aeolian system is used here as a conceptual framework for the dust monitoring programme. Three dust process-zones are identified, within which three basic aeolian processes operate: dust entrainment (primary and secondary), dust transport, and dust deposition (primary and secondary). Within each dust process-zone, standardized dust collection, measurement, and analysis techniques, are proposed for a network of monitoring sites. Entrainment and transport can be measured — directly using aerosol pump-samplers and indirectly by relating dust-aerosol concentration to solar radiation and visibility. The indirect approach has the advantage that it opens up a large body of historical data on dust and, therefore, desertification. Deposition can be measured using dust-traps. The importance of such aspects as site characteristics, measurement period, and laboratory methods, are also discussed. Finally, a minimal administrative structure is suggested, allowing for the possibility of UNEP or other major support.
The effects of inoculation with the plant growth-promoting rhizobacterium Azospirillum brasilense Cd on germination and growth of oak (Quercus ithaburensis Decaisne) seedlings were investigated in the nursery.An inoculum concentration of 107 colony forming units per plant of A. brasilense caused significant increases in seedling root surface area, root dry weight, foliage and shoot dry weight 30 days after inoculation.Inoculation of oak seedlings with A. brasilense is therefore suggested for improving the establishment, growth and development of oak seedlings under nursery conditions.