Juan Carlos Raya-Pérez’s research while affiliated with Instituto Tecnológico de Roque and other places

Actinobacteria belong to a group of abundant microorganisms in natural ecosystems. Out of these microorganisms, particularly from the species of the genus Streptomyces, most of the antibiotics that are used for human health have been characterized and identified. However, they are seldom used as antagonists in agricultural systems; despite it is plausible that species of Streptomyces can control important root pathogens. The objective of this study was to obtain the molecular identification and characterization of three Streptomyces strains by confronting them against phytopathogenic fungi and oomycetes, in order to determine the in vitro antagonistic potential and the effect of volatile compounds produced. The strains of Streptomyces were molecularly identified through the sequence of 16S of the RNAr such as: Streptomyces mauvecolor (B21), Streptomyces lasiicapitis (B22) and Streptomyces olivochromogenes (B37) which showed antagonistic potential in vitro against Rhizoctonia solani, Fusarium oxysporum and Phytophthora capsici. S. mauvecolor showed an average percentage of radial growth inhibition (PICR) for the three pathogens of 62.88 %, S. lasiicapitis of 98.72 % and S. olivochromogenes of 83.58 %. Similarly, out of the three pathogens, R. solani was inhibited in greater proportion by the three strains (93.85 %). A relevant fungistatic action was observed over P. capsici, an economically important oomycete, with 100 % inhibition at 24, 48 and 72 h of exposure with S. lasiicapitis, first reported as antagonist of root pathogens. The use of these species of Streptomyces with high levels of antagonism against pathogens of economically important crops, represents an alternative of low environmental impact.

La producción de trigo en México enfrenta una escasez de agua para riego, por lo que es necesaria la generación de germoplasma con menor necesidad hídrica, y evaluar nuevo germoplasma de trigo con mayor tolerancia a déficit hídrico. El objetivo de esta investigación fue evaluar la productividad de seis genotipos de trigo bajo dos calendarios de riego, durante tres ciclos de otoño-invierno (2013 a 2016). Se observó que los ciclos de evaluación tuvieron mayor impacto sobre la expresión de los días a madurez, número de espigas m-2, peso de mil granos, días a floración, granos m-2, número de granos por espiga y rendimiento unitario de grano. Del total de la variabilidad generada por los factores de estudio y sus interacciones, la del rendimiento fue explicada principalmente por los ciclos de evaluación, riegos, genotipos, así como por las interacciones ciclos × riegos, genotipos × ciclos y genotipos × riegos. Con cuatro riegos, los genotipos presentaron mayor número de días a madurez, así como una mayor cantidad de biomasa, mayor número de granos por espiga, mayor cantidad de espigas m-2 y mayor número de granos m-2; ésto permitió obtener 840 kg ha-1 más de grano con respecto a tres riegos. La variedad Bárcenas S2002 sobresalió en riego restringido al presentar menor número de días a floración y madurez del grano, y obtuvo el mayor rendimiento, mayor producción de biomasa, número de espigas por m2 , número de granos por m2 y peso de mil granos.

In recent years, benefits of silicon in plants grown under stress conditions have been reported. The objective of the research was to evaluate the response at a physiological and biochemical level of millet (Panicum miliaceum L.) to fertilization with Si under controlled stress conditions during vegetative stage, drought, salinity and the control (without stress). After stress, shoot and root length, DM content, peroxidase (POD) and catalase (CAT) activity, proline, H2O2 and Si content, seed yield and germination percentage were measured. Drought and salinity significantly decreased shoot (24%, 21%) and root (30% in drought) development, weight (36%, 29%) and seed number (30%, 21%) per plant. Application of Si significantly increased seed number (289) and seed weight (1.20 g) in the control plants, increased seed weight (0.83 g) in plants under drought and germination percentage (99%) in plants under salinity. Silicon increased 2.1 times POD activity in drought, 1.4 times in salinity and control plants; CAT activity increased 10.6 times in salinity and 1.7 times in control plants. Silicon decreased 10 times proline levels in plants under drought; in salinity and control, proline content increased 1.3 times with Si and H2O2 levels decreased in these treatments. The Si content in plants fertilized with Si under drought, salinity and control was 6%, 3.54% and 5.45% respectively. In conclusion, Si can improve plant stress tolerance by stimulating POD and CAT activity, and regulating proline levels, allowing it to improve the production and physiological seed.

The Trichoderma harzianum fungus is one of the most widely used biological control agents in agriculture. A new T. harzianum THITR01 strain was isolated and their spores were mutagenized with ethyl methane sulfonate obtaining 174 mutants. M7, M14, M21 and M24 are mutant strains that showed 97.4%-100% antagonist effect against Sclerotium rolfsii, Rhizoctonia solani and Sclerotinia sclerotiorum compared to the wild strain. Under potato dextrose agar (PDA) medium with either NaCl, sorbitol or NaHCO3 there were nonsignificant growth rate differences between the mutants and the wild strain. M14 and M21 mutant strains were inoculated on ‘Jalapeño’ pepper plants (Capsicum annuum L. var. annuum) with unavailable P promoted a significant increase in root fresh weight (54% and 40%, respectively) and dry weight (28% in both strains), compared to plant inoculation with the wild strain. The M14 strain presented the highest P solubilization ability (13.4 μg g-1) in the substrate and promoted a change on root architecture. There was a higher relative water content (82.9%) in drought stressed plants inoculated with the M24 mutant than in plants that were inoculated with the wild type strain (76.3%), and also higher levels of proline in chili pepper plants inoculated with the M24 mutant (939.5 μg g-1 dry weight) than in plants inoculated with the wild type strain (419.8 μg g-1 dry weight). Therefore, M14, M21 and M24 mutant strains could potentially be used as biocontrol agents and plant protector from abiotic stress.

Tomatoes are an important dietary source of lycopene, a natural antioxidant compound that contributes to reducing reactive oxygen species (ROS); however, the lack of a food matrix can result in their rapid degradation during storage. Therefore, the aim of this work was to evaluate the physicochemical, antioxidant, and stability properties of lycopene and β-carotene in encapsulated tomato juice (TJ) obtained by freeze-drying. Maltodextrin (MD) and gum arabic (GA) were used as wall materials. Two formulations were obtained: MD:GA:TJ (3:1:14) and MD:- GA:TJ (1:3:14), and were both compared with three controls: MD:GA (3:1), MD:GA (1:3), and freeze-dried TJ without wall materials. The physicochemical properties, lycopene, and β-carotene content were evaluated; also, antioxidant activity was measured by DPPH and ABTS assays. Carotenoid stability during storage was also evaluated. The encapsulates presented maximum concentrations of lycopene and β-carotene of 17.86 and 1.90 mg/100 g, respectively, and an antioxidant activity that varied from 5.14 to 20.98 µM Trolox/g. Good hydration, water solubilization, and color properties were observed in the encapsulates. The MD:GA:TJ (3:1:14) treatment presented the best antioxidant and stability characteristics during storage.

Artículo de revisión RESUMEN Entre los insectos existe una gran variedad de especies y muchas de ellas tienen la capacidad de interaccionar con el mundo vegetal. Este tipo de interacciones van desde aquellas de carácter mutualista hasta las antagónicas. El tipo de interacciones planta-insecto puede deberse en gran medida a la adaptación que tenga el insecto hacia los metabolitos de la planta, especialmente (parte de los "mecanismos de defensa") aquellos que le son potencialmente dañinos. Los insectos que son capaces de sobrepasar estas barreras poseen, a su vez, poseen "mecanismos de contra defensa" que les permiten tal adaptación. Los insectos para sobrevivir han desarrollado una serie de mecanismos de defensa que les permite un desarrollo adecuado u óptimo en los diferentes ambientes. Uno de los mecanismos que más ha llamado la atención por su aplicación potencial es la presencia de genes que codifican para proteínas con actividad proteolítica, las cuales son clave para digerir los alimentos que consumen los insectos. En esta revisión se aborda la interacción de los insectos con las plantas, su adaptación, el rol de las proteasas y los métodos que actualmente se utilizan para combatir a los insectos plaga causantes de grandes pérdidas en los cultivos de interés agrícola. Palabras clave: proteasas, manejo integrado de plagas, agricultura sostenible ABSTRACT Insects present a great variety of species and many of them have the ability to interact with the plant world. These interactions range from those of a mutualistic nature to antagonistic ones. The type of plant-insect interactions, may be largely due to the adaptation that the insect has to the metabolites of the plant (part of the "defense mechanisms") that are potentially harmful. Therefore, the insects that are capable of overcoming that barrier in turn, have "counter defense mechanisms" that allow such adaptation. Insects to survive have developed a series of defense mechanisms that allow them to develop adequately or optimally in different environments. One of the mechanisms that has most attracted attention is the presence of genes that code for proteins with proteolytic activity, which are key to digest the food that insects consume. This review addresses the interaction of insects with plants, their adaptation, the role of proteases and the methods currently used to combat insect pests that cause large losses in crops of agricultural interest.

Globally, drought is the main factor that reduces common bean yield. For this reason, breeding alternatives, such as molecular marker-assisted selection, that focus on various functional genes directly involved in the response to water stress, such as those encoding late embryogenesis abundant (LEA), early response to dehydration (ERD), and dehydrin proteins, have been implemented. The aim of this study was to identify differentially expressed genes of Phaseolus vulgaris in drought-tolerant cultivars Pinto Saltillo (PS) and Pinto Villa (PV), and drought-susceptible cultivars Bayo Madero (BM) and Canario 60 (C60) in vegetative and reproductive stages. Relative water content (RWC) in leaf tissue was measured. Twenty-eight P. vulgaris genes obtained from GenBank and from a subtractive suppressive library from the PS cultivar were analysed, and their expression profiles were examined by reverse transcription polymerase chain reaction (RT-PCR). Then, cDNA arrays were developed and hybridised to confirm expression which was finally validated by quantitative PCR (qPCR). The usefulness of the identified genes as selection criteria for the tolerance of different genotypes to drought was examined using cDNA arrays. Expression of 21 genes was induced by drought. The cDNA arrays confirmed that expression of 19 of these genes increased in the vegetative stage upon exposure to the drought, and a higher expression was observed in the reproductive stage compared with vegetative stage V4. Only five genes induced by the drought were found to have a lower expression in the susceptible cultivars compared with the tolerant ones. During recovery after the drought in the reproductive stage, 13 of the 21 induced genes remained transcriptionally active including LEA3 and dehydrin. The RWC during the drought in vegetative stage V4 decreased by about 55 % in all cultivars, but at the onset of flowering, it increased to 80 % in PV and PS. In contrast, in the susceptible cultivars, it remained at 55 %. Using qPCR validation, expression induction was confirmed in the drought-tolerant cultivars. Polyubiquitin2, LEA3, LEA4, and dehydrin were useful genes for selecting drought-tolerant genotypes under field conditions. Additional key words: dehydrin, expression patterns, LEA, qPCR, relative water content.