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Diseases of Celosia
Abstract
Celosia (Celosia L.), generally known as cockscomb or woolflower, is a genus of ornamental and edible tender annuals in the Amaranthaceae. Ornamental cultivars are subject to few diseases, although fungal and bacterial leaf spots, Botrytis blight, Rhizoctonia root and stem rot, damping-off, and root-knot nematode may occur where humidity is high or where good growing practices, sanitation, and other cultural disease management practices that reduce inoculum and spread of propagules are not followed.
... Another damage caused due to the constant presence of invasive plants in the areas of agricultural crops includes the increase in production management costs, from the preparation of the soil for planting as well as during the harvest, which requires an operational change for its elimination (Pitelli, 2015). In addition, the presence of these plants contributes to the hostility of plant pathogens, including nematodes, since several invasive species are hosts of these organisms, serving as a source of inoculum, helping in the dissemination and survival (Carvalho, 2013;Gould, 2017). ...
Celosia argentea is a plant well adapted to the conditions of tropical and subtropical climates, being widely used for medicinal purposes and having high economic value for some regions. Infections caused by Meloidogyne spp. stand out as one of the main phytosanitary problems of C. argentea, with this, the work aimed to identify Meloidogyne species associated with Celosia argentea in areas in the municipality of Guaramiranga, CE, Brazil. The collections were made from roots with galls. Subsequently, the species were characterized through the morphology, esterase phenotypes and molecular analysis of the ITS and 28S rDNA regions. Plants of C. argentea were kept under greenhouse conditions, inoculated with the population of M. javanica (Ms01). The control treatment was not inoculated. The inoculated plants showed root gall symptoms, while the non-inoculated plants showed no symptoms. The species M. javanica was identified. This is the first detection of Meloidogyne javanica in Celosia argentea in Northeast Brazil.
▶ The book presents in details the most advanced and recent information on Botrytis – plant interactions ▶ Botrytis is a very well-studied pathogen using state of the art techniques ▶ The book contains chapters written by leading scientists from various scientific disciplines studying Botrytis as a fungus and as a pathogen Botrytis, a genus of fungal plant pathogens, is the focus of intensive scientific research worldwide. The complex interactions between these pathogens and the plants they infect (referred to collectively as the pathosystem) and the economic importance of the diseases caused by Botrytis on more than 1400 species of cultivated plants, many of which are important agricultural crops, render this pathogen of particular interest to farmers, agriculture experts, advisers, extension staff, students and researchers worldwide. This book is the product of intensive work by 41 authors, all of whom are leading scientists from various scientific disciplines studying Botrytis as a fungus and as a pathogen. The authors of this book have amassed state-of-the art knowledge on diverse topics, including Botrytis epidemiology, disease management, biological and chemical control and aspects of the plant-pathogen interactome, including virulence factors and defense processes, signaling cascades, the oxidative burst and general biological aspects, such as vegetative incompatibility, mycoviruses, and the revised Botrytis species concept. This book also provides reviews of the genetic and post-genomic analyses, such as transcriptomics and proteomics, used to study Botrytis biology and pathogenicity. This 20-chapter book is a comprehensive treatise covering the rapidly developing science of Botrytis and reflecting the major developments in studies of this fungus. It will serve as a source of general information for specialists in agriculture and horticulture, but also for students and scientists interested in the biology of this fascinating, multifaceted phytopathogenic fungal species.
Phytoplasmas are microorganisms associated with severe plant diseases affecting diverse agrarian activites worldwide. Since their discovery, conclusive proof of their pathogenicity is lacking due to failure to culture these organisms. This has also hindered studies on their biology, biochemistry and physiology, although significant taxonomic progress has been achieved from study of the 16S ribosomal gene and full genomic sequencing of four phytoplasma strains. The inability to fulfil Koch's postulates severely restricts the understanding of the roles of these organisms in plant diseases and in plant/insect/phytoplasma interactions. Here we show that specific commercial media support axenic growth of phytoplasmas under defined conditions; the identity of the organisms was confirmed by PCR/RFLP analyses and sequencing of phytoplasma-specific genes. We have demonstrated for the first time that phytoplasmas, similarly to mycoplasmas, can grow independently from their host(s). This should assist reduction of the socio-economic impact of phytoplasma diseases worldwide through improved pathogen detection and consequently better management of the diseases they cause. Knowledge of mechanisms underlying the autonomous life of phytoplasmas, that are among the smallest living organisms, should also provide important information about basic mechanisms of life.
The genus Cercospora represents a group of important plant pathogenic fungi with a wide geographic distribution, being commonly associated with leaf spots on a broad range of plant hosts. The goal of the present study was to conduct a morphological and molecular phylogenetic analysis of the Cercospora spp. occurring on various plants growing in Northern Thailand, an area with a tropical savannah climate, and a rich diversity of vascular plants. Sixty Cercospora isolates were collected from 29 host species (representing 16 plant families). Partial nucleotide sequence data for two gene loci (ITS and cmdA), were generated for all isolates. Results from this study indicate that members of the genus Cercospora vary regarding host specificity, with some taxa having wide host ranges, and others being host-specific. Based on cultural, morphological and phylogenetic data, four new species of Cercospora could be identified: C. glycinicola (from Glycine max), C. cyperacearum and C. cyperina (from Cyperus alternifolius), and C. musigena (from Musa sp.). The most common Cercospora sp. found in Northern Thailand was C. cf. malloti, which occurred on a wide host range. Several collections could not be resolved to species level due to the lack of reference cultures and DNA data for morphologically similar species. Further collections from other countries are needed to help resolve the taxonomy of some species complexes occurring on various plant hosts in Thailand.
Because of the importance of ornamental plants culture in north of Iran, and the outbreak of suspicious symptoms of phytoplasma diseases on these plants, a study was carried out in order to detect and identify phytoplasmas associated with them. The presence of phytoplasma in samples of cockscomb, tagetes and rose plants was shown by direct and nested-PCR assays using the phytoplasma-specific primers, P1/P7 and R16F2n/R2. Sequences of cockscomb, Indian marigold and rose phytoplasmas have high homology with the members of aster yellows phytoplasma group (16SrI). Phylogenetic analysis showed that cockscomb, tagetes and rose phytoplasmas are closely related to 16SrI-M the first one and 16SrI-B the latter two, respectively. To our knowledge, this is the first report of a member of 16SrI group phytoplasma infection in cockscomb in Iran. Moreover, the present study is the first report of phytoplasma disease outbreak on rose in north of Iran by subgroup classification of the associated phytoplasma.
Recently, yellows diseases have become more common in Israel, and phytoplasmas have been detected in some of these diseased crops. Commercial fields of two celosia species (Celosia plumosa L. and C. cristata L.) also have exhibited yellows symptoms and total crop failure. Typical mycoplasma-llke bodies were observed in infected but not in healthy plants. The same plants were analyzed for the presence of phytoplasma by polymerase chain reaction (PCR), using the universal oligonucleotide pair r16SF2/r16SR2, followed by nested PCR using group-specific primers. Restriction analyses performed with these products indicated that two different types of phytoplasmas are infecting celosia. PCR-RFLP analysis of one type revealed a restriction pattern typical of aster yellows. Similar analysis of the second type indicated possible relatedness, though not identity, to the pattern of phytoplasmas of the Western-X group. This is, to our knowledge, the first report of phytoplasma infection in celosia.
Distribution and host range data of Cercospora-like hyphomycetes from Brunei Darussalam are summarized in the present paper. Pseudocercospora bruneiensis sp. nov. on Aglaonema sp., P. jasminicola var. effusa var. nov. on Jasminum sambac, P. pangiicola sp. nov. on Pangium edule, and Stenella orchidacearum sp. nov. on Vanda sp. are described, and the new combinations Passalora caladii, Pseudocercospora caseariae, and P. thunbergiae are introduced. Cercoseptoria caseariae is reduced to synonymy with Pseudocercospora samydacearum.
Collar rot induced by Macrophomina phaseolina, recently appeared as one of the most significant constraints to the production
of Cockscomb (Celosia argentea L.), an ornamental plant. Symptoms include, wilting of the plant, chlorosis of lower leaves,
shrinking of stem at collar region, which becomes black at later stage and affected plant become shredded, consequently a
clear mycelial growth of the fungus can be seen if the stem of the affected plant is split open. In this study, the causal fungus
was isolated from the diseased tissues (collar and stem regions, externally and internally). Then the pathogenicity test of
isolated pathogens was confirmed through Koch’s postulates. Considering the management trials, five fungicides
(Carbendazim, Thiophenate-M, Ridomil Gold, Antracol and Score) and five different plant extracts (Azadirachta indicia L.,
Melia azedarach L., Eucalyptus cameldulensis L., Syzygium cumini L. and Moringa oleifera L.) were evaluated against the
collar rot disease pathogen (Macrophomina phaseolina) by poison food technique at different concentrations viz., 100, 150,
200 and 250 μg/mL for fungicides and 10, 15 and 20% for plant extracts. Out of five fungicides used, Topsin M and Antracol
were found to be most effective in reducing the mycelial growth of M. phaseolina by (83%) and (76%) followed by Ridomil
Gold, Score and Carbendazim (46, 39 and 29% reduction). In case of plant extracts, A. indicia and E. cameldulensis extracts
were more effective by reducing the mycelial growth of M. phaseolina by 77 and 74%, respectively, followed by M. oleifera,
M. azedarach, and S. cumini (61, 45 and 18% reduction). © 2015 Friends Science Publishers
The ability of disease-suppressive rotation crops to reduce potato disease
problems and increase crop productivity in a field with prior severe
Verticillium wilt, as well as the potential influence of previous
cropping history on disease suppression, was evaluated over three field
seasons in Maine. Disease-suppressive rotations consisted of: (i) a
high-glucosinolate mustard blend (‘Caliente 119’) as a mixture of
white mustard (Sinapis alba) and oriental mustard (Brassica juncea)
with known biofumigation potential and (ii) a sorghum-sudangrass
hybrid. Each were grown as single-season green manures followed by
a subsequent potato crop. These rotations were compared with a standard
barley rotation and a barley rotation followed by chemical fumigation
with metam sodium as controls. Both green manure rotations
significantly reduced (average reductions of 25 and 18%, respectively)
Verticillium wilt in the subsequent potato crop compared with the standard
barley control but were not as effective as chemical fumigation
(35% reduction). The mustard blend also reduced other soilborne diseases
(black scurf and common scab) better than all other rotations.
Mustard blend and chemical fumigation treatments increased tuber
yield relative to the barley control by 12 and 18%, respectively. However,
by the second rotation cycle, disease levels were high in all rotations,
and only chemical fumigation resulted in substantial disease
reduction (35%). Rotations also had significant effects on soil microbiology,
including soil bacterial and fungal populations and microbial
community characteristics based on fatty acid profiles. However, only
chemical fumigation significantly reduced soil populations of Verticillium
spp. and increased general soil microbial activity. Previous cropping
history did not significantly affect disease reduction, tuber yield,
or soil microbial communities. This research indicates the potential for
using disease-suppressive rotations for managing Verticillium wilt and
other soilborne diseases but also indicates that multiple years of disease-
suppressive crops may be needed to substantially reduce disease
in heavily infested fields.
A greenhouse study was conducted to determine the pathogenic effect of Cucumber mosaic virus (CMV) and Putative Bitterleaf mosaic virus (BLMV) on a local variety of Celosia argentea. The viral inoculi were extracted by homogenization from infected leaves of cowpea and bitterleaf that were obtained from the International Institute of Tropical Agriculture (IITA) Ibadan. Seeds of Celosia argentea were sown in plastic pots that were filled with sandy loam soil, previously steam sterilized at 1200C for 2hours. The plants were mechanical inoculated 3weeks after planting with either CMV, BLMV or Buffer (control). Each treatment was replicated 4 times in a Completely Randomized Design (CRD) manner. The results of the experiment revealed that the C. argentea was susceptible to infection with CMV and BLMV. Percentage severity of the viral infections were significantly different (p=0.05) compared with the control. The results indicated that CMV had the significantly highest effect on percentage disease severity (53.1%), followed by BLMV (16.5%)and control plants had no infection. Subsequent growth and yield attributes in the virus inoculated plants were also generally lower than those recorded for the control. The significantly lowest stem girths were recorded in plants inoculated with CMV (1.6cm), followed by BLMV (2.8cm), while the significantly highest stem girths were obtained in the control plants (4.2cm). The study found C. argentea to be susceptible to infection by CMV and BLMV and thus advocates the need for effective control measures for high productivity of the vegetable.
The effects of neem compost on root knot nematode, Meloidogyne incognita, pest of Lagos spinach, Celosia argentea, cv. TLV 8, was studied during 2010 and 2011 planting seasons on the field. The trial was conducted at the Teaching and Research Farm of Ladoke Akintola University of Technology, Ogbomoso, Nigeria. There were four treatments, replicated five times fitted into randomised complete block design. Neem compost was applied at 1.0, 1.5 and 2.0 tonnes/ha. Experimental plots, where no compost was applied served as the control. The result obtained shows that Lagos spinach treated with neem compost significantly (p < 0.05) reduced the final soil nematode population and root infections (damage), with resultant improvement on crop growth and yield. The result of the chemical analysis of the neem compost revealed the presence of flavonoids, sterols, glycosides, alkaloids and saponins.
Seedlings of several annual and perennial bedding plant species were inoculated with an isolate of Phytophthora nicotianae (synonym = P. parasitica) and planted into field beds in a simulated landscape situation. Throughout the growing season, growth measurements and disease ratings of the inoculated plants were compared with those of non-inoculated control plants of the same species in identical beds. Phytophthora-inoculated plants that continued to thrive through most of the growing season included Ageratum houstonianum, Celosia ‘Apricot Brandy’, and ‘New Look’; Dahlia ‘Harlequin’; Eustoma grandiflorum (prairie gentian); Lobularia ‘Carpet of Snow’; Nicotiana ‘Alta Dwarf White’, ‘Domino Salmon’, and ‘Nicki Red’; Pelargonium (geranium) ‘Multibloom Scarlet Eye’; Petunia ‘Polo Salmon’, and ‘Sugar Daddy’; Portulaca ‘Sundial Peppermint’; Rudbeckia ‘Rustic Dwarf’; Salvia ‘Lady in Red’, and ‘Victoria Blue’; Tagetes (marigold) ‘Disco Mix’, ‘Inca Orange’, ‘Inca Yellow’, ‘Janie Harmony Improved’, and ‘Gold Fireworks’; and Zinnia angustifolia. Plants that performed poorly following inoculation with Phytophthora include Antirrhinum (snapdragon) ‘Liberty White’, and ‘Liberty Mix’; Catharanthus (vinca) ‘Little Bright Eye’, and ‘Tropicana Rose’; Hibiscus ‘Disco Belle Mix’; Impatiens ‘Accent Bright Eye’; Leucanthemum x ‘Alaska’; Melampodium ‘Medallion’; Salvia ‘Turkestanica’; Torenia ‘Clown Mix’; Verbena ‘Imagination’; and Viola (pansy) ‘Fama See Me’. This study identifies bedding plant taxa which will provide an acceptable display in landscape beds infested with Phytopthora nicotianae (synonym = P. parasitica).
The current and pending restriction on the use of soil fumigants and other nematicides effective in controlling nematodes in field grown floriculture crops has increased the importance of determining the relative susceptibility of these crops to important species of root-knot nematodes. Greenhouse experiments were performed to assess the susceptibility of several floriculture crops grown in Florida to the three most common species of root-knot nematode, Meloidogyne arenaria, M. incognita, and M. javanica. Root growth and health, as well as nematode galling and egg production were evaluated for Celosia argentea (cockscomb), Delphinium elatum (larkspur), Antirrhinum latifolium (snapdragon), and Helianthus annuus (sunflower). A susceptible host, Solanum lycopersicum ('Rutgers', tomato), was included in all trials for comparison. Most of the floral crops tested were highly susceptible to all three species of rootknot nematodes. Delphinium was not tested for susceptibility to M. arenaria but was consistently less susceptible to M. incognita and M. javanica than the other floral crops tested with those nematode species. Results of these greenhouse trials are consistent with observations from field trials on alternative fumigants conducted in Florida in which low levels of galling by root-knot nematodes were consistently observed on Delphinium.
Four commercial leafy vegetable farms in Lagos State were surveyed from October 1989 to September 1990 for the occurrence and prevalence of leafy vegetable viruses. Mechanically transmissible viruses were isolated from Amaranthus hybridus, Celosia argentea, Cucurbita moschata, Telfairia occidentalis and Brassica oleracea, while virus-like symptoms (causal agents not sap-transmissible), were observed on Solanum macrocarpon. Two previously uncharacterized viruses, one each from C. argentea and C. moschata were isolated. The identification of viruses such as telfairia mosaic virus (TeMV) and amaranthus mosaic virus (AMV), that had been reported in the literature, were confirmed on the basis of host range, symptomatology, insect transmission and particle morphology. Virus-like symptoms were not observed on Corchorus olitorus and five other exotic vegetables. Amaranthus mosaic virus and celosia mosaic virus (ClMV), the latter isolated for the first time in Nigeria in the course of this study, were recorded from all the farms and were therefore the most prevalent. The incidence of AMV was 19.7% at Amuwo Odofin while it was 0.7% and 0.6% at Tejuoso and Abule Ado farms respectively. For ClMV, an incidence of 27.5% was recorded at Amuwo Odofin while Tejuoso and Abule Ado had 0.6% and 1.4% respectively. Telfairia mosaic virus and viruses on C. moschata and B. oleracea were limited to the Tejuoso farm. Generally, virus incidence was higher during the wet season for most of the viruses. Elimination of plant remains and volunteer crops may be exploited in the control of the viruses.
KEY WORDS: Survey, Leafy vegetables, viruses.
Global Jnl Pure & Applied Sciences Vol.10(1) 2004: 61-67
The fungal genus Botrytis is the focus of intensive scientific research worldwide. The complex interactions between this pathogen and the plants it infects and the economic importance of the diseases caused by Botrytis (principally grey mould) on more than 1400 species of cultivated plants pre- and post-harvest, render this pathogen of particular interest to farmers, advisers, students and researchers in many fields worldwide. This 20-chapter book is a comprehensive treatise covering the rapidly developing science of Botrytis and reflecting the major developments in studies of this fungus. It will serve as a source of general information for specialists in agriculture and horticulture, and also for students and scientists interested in the biology of this fascinating, multifaceted phytopathogenic fungal species.
Under warm and dry growing conditions of the Indian arid region, Macrophomina phaseolina (Tassi) Goid., a soil borne plant pathogen, causes charcoal rot in legumes and oil seeds limiting profitable production. Due to lack of resistant cultivars, cultural and biological methods of management are the only option left with the growers of the region. Amending soil with certain weed residues or compost prepared from residues of mesquite (Prosopis juliflora (Swartz) DC) has been advocated for managing Macrophomina in arid regions. In sequel, an effort was made in the present study to integrate native bio-agents in compost in order to improve pathogen control and to induce soil suppressiveness. Four composts were prepared from residues of P. juliflora, neem, Indian mustard and weeds (Euphorbia hirta, Aerva persicae and Celosia argentia). Population of antagonistic actinomycetes to M. phaseolina was maximum (37% increase) in mustard + weed residue compost. In other composts also, there was enhancement in the population of antagonistic actinomycetes compared to non-amended control. Maximum reduction (86.3%) in population of M. phaseolina was estimated in mustard + weed compost amended soil followed by mustard compost (78.4%). Combining weed compost with any compost has improved reduction in M. phaseolina population compared to compost alone. In a two-year field study on cluster bean, incorporation of composts alone or in combination with weed compost were found significantly effective in reducing charcoal rot incidence compared to control. On the basis of two years pooled average, least disease incidence (4.9%) was recorded in P. juliflora + weed compost (3.5+0.5 t ha-1) followed by mustard + weed compost (5.2%) compared to control (10.1%). Significant reduction was estimated in soil amended with mustard + weed compost (70 cfu g-1 soil) followed by P. juliflora and P. juliflora + weed compost at 0-15 cm soil depth after two years of continuous compost incorporation. This study demonstrates that bio-control agent enriched composts improve pathogen and disease control. This can be considered as a low input soil disinfestation alternative for rain fed agriculture.
Michigan ranks third in the United States for the wholesale value of floriculture products, with an estimated value of $375.7 million. Seedling damping-off and root and crown rot are commonly caused by Pythium spp. and are important problems for greenhouse growers. Pythium spp. associated with Michigan's floriculture crops were characterized as a means to improve current management strategies. During 2011 and 2012, potted poinsettias with root rot symptoms were sampled from nine greenhouses located in Kent, Kalamazoo, and Wayne counties. In 2013, from the same three counties, symptomatic geranium and snapdragon bedding plants were sampled from 12 greenhouses. Additionally, symptomatic hibiscus and lantana plants were sampled at one greenhouse facility. Isolates were confirmed to be Pythium spp. via morphology and sequencing of the ITS region. A total of 287 Pythium spp. isolates were obtained from poinsettias and 726 isolates from geranium, snapdragon, hibiscus, and lantana. Seven Pythium spp., and a group of isolates determined as Pythium sp. 1 were identified. The most prevalent species were P. irregulare, P. ultimum, and P. aphanidermatum. A subset of isolates was chosen for pathogenicity and mefenoxam sensitivity testing. Six of the species were virulent to germinating geranium seeds. Most P. ultimum and P. cylindrosporum isolates tested were intermediate to highly resistant to mefenoxam, whereas most P. aphanidermatum isolates were sensitive. This study suggests that Pythium spp. recovered from Michigan greenhouses may vary depending on the host, and that mefenoxam may not be effective to control P. ultimum or P. cylindrosporum.
Cotton, being a long duration, widely spaced and relatively slow growing crop during early growth stages, is subjected to severe weed menace. Weed infestation in cotton has been reported to offer severe competition and causing yield reduction to an extent of 40 to 85 per cent. Weeds which emerge with cotton plants offer a severe competition and bring about considerable reduction in seed cotton yield. Reduction in seed cotton yield under irrigated conditions is primarily due to nutrient depletion caused by weeds and may vary over from 10–90 per cent Weed infestation in cotton has been reported to offer severe competition and causing yield reduction to the extent of 74 per cent. Weeds are considered as a major biotic constraint for high production. The weeds which germinate before or simultaneously with the crop are frequently capable of forming a leaf canopy over cotton. Late emerging weeds may interfere with cotton defoliation and harvest and may lower lint grade due to lint staining and to excessive foreign material. A brief review of literature on weed flora, the effect of weed management practices on growth, yield and quality characters of cotton are presented here under.
A tobamovirus, Ribgrass mosaic virus (RMV), was identified newly from chinese cabbage (Brassica campestris L. pekinensis) in Korea. Virus disease incidence of RMV on chinese cabbage was 37.9% in alpine area on August in 1993. RMV induced the symptoms of necrotic ring spots, necrotic streak on midrib and malformation. RMV, Ca1 and Ca3 isolate, could infect 35 species out of 45 plants including Chenopodium amaranticolor. Physical properties of RMV Ca1 isolate were very stable as 10(-8) over for dilution end point, 95 C for temperature inactivation point and 18 weeks for longevity in vitro. RMV had the soil transmission rate of 75.0% for the chinese cabbages, 'Chunhawang' and 'Seoul' cultivars. The purified virions of RMV had the typical ultraviolet absorption spectrum of maximum at 260 nm and minimum at 247 nm. RMV of Ca1 isolate was related serologically with antisera of Tobacco mosaic virus (TMV)-Cym, TMV-O and Pepper mottle virus, but not related with antiserum of Odontoglossum ring spot virus. coat protein gene of RMV-Ca1, sized 473 nucleotides, encoded 158 amino acid residues. Nucleotide identity of RMV-Ca1 CP gene was 96.4% with RMV-Shanghai (GenBank accession No. of AF185272) from China and 96.0% with RMV-Impatiens (GenBank accession No. of AM040974) from Germany. Identity of amino acids between RMV-Ca1 and the two RMV isolates was 96.8%. Specific three primers were selected for rapid and easy genetic detection of RMV using Virion Captured (VC)/RT-PCR method.
Control of Tospoviruses remains problematic. Cultural practices and varietal selection have proven effective in minimizing losses due to TSWV in some field crops. A series of risk factors including prior history, planting date, cultivar selection and plant and row spacing have been identified as critical factors in peanuts. In other high-risk areas, such as Hawaii, highly susceptible crops cannot be grown profitably. In greenhouse grown crops, such as floral crops, extreme measures including screening of production areas with fine-meshed cloth, preventative thrips management strategies and use of propagation material shown to be free of TSWV and INSV are necessary for control of these viruses. While forms of resistance have been introduced into various crops, they have nearly always been overcome by the rapid occurrence of resistance-breaking strains of the virus. TSWV is thought to exist in nature as a complex heterogeneous mixture of distinct isolates that can exchange genetic information through reassortment of genome segments. This provides a readily available reservoir of genetic information to facilitate adaptation.
Symptoms associated with infection by the tomato spotted wilt virus (TSWV) were documented among bedding, potted, perennial, and foliage plants growing in commercial greenhouses in Pennsylvania. Previously unreported hosts were identified, including four bedding, seven potted, 16 perennial, and seven foliage plants. Of 316 bedding plants infected, 95% were infected with the impatiens strain of TSWV (TSWV-I), and impatiens (Impatiens wallerana) and begonias (Begonia spp.) were most frequently infected (.)
Root-knot nematodes were first reported in 1855 by Berkeley, who observed them causing damage on cucumbers. Until Chitwood's work in 1949, which defined 4 species and one subspecies (M. incognita acrita) within the genus Meloidogyne, the root-knot nematodes were all considered the same species, Heterodera radicola. In an 1887 paper (reprinted in 1892) Goeldi described Meloidogyne exigua, the type species of the genus. From this description, Chitwood obtained the name we currently use for the root-knot nematodes. The name Meloidogyne is of Greek origin, meaning "apple-shaped female." Approximately 100 species of Meloidogyne have been described. The most widespread and economically important species are M. incognita, M. javanica, M. arenaria, M. hapla, M. chitwoodi and M. graminicola. Root-knot nematodes are primarily tropical to sub-tropical organisms, however M. hapla and M. chitwoodi are well adapted to temperate climates.
Jepson, S.B. 1987. Identification of Root-Knot Nematodes (Meloidogyne Species). CAB International, Wallingford, UK.
Viaene, N.M. 1998. Management of Meloidogyne hapla on lettuce in organic soil with sudangrass as a cover crop. Plant Disease 82:945-952.
Despite the continued interest of mycologists and plant pathologists, the taxonomic position of the economically important, plant pathogenic species of Sclerotinia has remained unresolved. Over 250 species of diverse relationships, both pathogenic and non-pathogenic, have been assigned to the genus Sclerotinia with consequent controversy and confusion over generic limits (Kohn, 1979a). Attempts to delimit the pathogenic species assigned to the genus using a few traditional characters have resulted in recognition of too many or too few species in relation to what is now known about the biology and micro-anatomy of this group to satisfy the practical need of the plant pathologist to name the pathogen in hand. Examination of type specimens of preserved material as well as observation of living isolates in the light of micro-anatomical and cultural characters employed by contemporary discomycotina taxonomists has resulted in the delimitation of plant pathogenic species of Sclerotinia in the revised and more limited circumscription of the genus presented.
Arabis mosaic virus (ArMV) is pathogenic to a wide variety of plant species including ornamen-tals. Using the methods of test-plants, electron microscopy, and DAS-ELISA, ArMV was identi-fied in ornamental plant species of the genera Arum L.. In naturally infected host plants, the virus was found in mixed infections with other viruses. Virus idenstity in five ornamental species was confirmed by RT-PCR.
The aim of this study was to evaluate the occurrence of peony ring spot disease in the collections of foreign and Lithuanian origin peony cultivars and hybrids and to identify a causal agent of this viral disease. During surveys of ornamental plant collections grown in Lithuania, solitary instances of affected by peony ring spot disease plants have been detected in all collections surveyed. Diseased plants occurred in the similar frequency in cultivars of foreign and Lithuanian origin from species Paeonia lactiflora, P. lutea, P. officinalis, P. suf-fruticosa. Samples of diseased plants were collected for investigation of disease causal agent. Virus was isolated and identified using classical virological (test-plants, electron microscopy) and modern molecular biology (DAS-ELISA, RT-PCR) methods. Inoculated test-plants ex-pressed reaction characteristic to Tobacco rattle virus (TRV); electron microscopy investiga-tion revealed characteristic to this virus rod-shaped particles of two modal lengths. Data of DAS-ELISA and RT-PCR confirmed TRV infection in naturally infected peony plants and in inoculated test-plants. Introduction. Genus Paeonia L. has been attributed to Paeoniaceae family. There are 40 species in this genus of beautiful perennials and shrubs. The genus name goes back to classical Greek and arose from the mythological God Peon – the protector of human health and doctors. Peonies are all deciduous and have long-lived, rather woody rootstocks with swollen roots, and large compound leaves with leaflets usually toothed or lobed. Each stem in spring terminates in one to several large, rose-like flowers. Their centers are the mass of short stamens that almost conceal the 2 to 5 large ovaries, which develop into short pods containing large seeds. The flowers are mostly in shades of pink or red, but there are also white and yellow-flowered species. The great majority of peonies are herbaceous, dying back to the ground in autumn, but there is a small group of Chinese species, known as the tree peonies – shrubs (Cheifetz et al., 2004).
The fungus Macrophomina phaseolina is a causative agent of diseases in more than 500 plant species. The fungus is primarily soil‐inhabiting but is also seed‐borne in many crops including soybean. It survives in the soil mainly as microsclerotia that germinate repeatedly during the crop‐growing season. Low C : N ratio in the soil and high bulk density as well as high soil moisture content adversely affect the survival of sclerotia. The disease can be managed to some extent by cultural practices, organic amendments, seed treatment and genetic host resistance. The scattered literature on these aspects is reviewed in this paper.
Ornamental plants of Celosia argentea L. and Celosia spicata L. displaying typical phytoplasma‐induced symptoms were observed in Piracicaba, State of São Paulo, south‐eastern Brazil. Our aim was to identify the possible phytoplasma involved. PCR revealed the association of phytoplasma with diseased plants of both species. Based on actual and virtual RFLP analysis and phylogenetic analysis, the phytoplasma was characterized as a member of the 16SrIII‐J subgroup. Transmission of the pathogen by dodder supported the evidence that the symptoms observed in naturally diseased plants were induced by a phytoplasma. Our results show that C. spicata is a new host for phytoplasma and that this is the first report of a 16SrXIII‐J phytoplasma infecting plants of C. argentea and C. spicata in Brazil.