ABSTRACT
The fungus Corynespora cassiicola, the causal agent of the target spot in soybeans, has been considered, from the seed pathology point of view, a seed-borne pathogen of limited importance. Therefore, little importance has been given to the role of the seeds in the transmission of this pathogen. The objectives of this study were to determine the incidence of C. cassiicola in soybean seeds and evaluate the effects of this seed-borne pathogen, inoculated in the seeds, concerning to physiological and epidemiological parameters. The experiments were carried out at TAGRO and Embrapa Western Agriculture under lab (blotter test and seed germination test) and greenhouse conditions (growing on test). The fungus C. cassiicola was detected in 11.3% of the 639 seed samples analyzed, with an average incidence of 0.91% and a maximum of 8.5%. The transmission of C. cassiicola from the seeds to above-ground parts of soybean seedlings was demonstrated, by pathogen establishment on the cotyledon, showing circular lesions with concentric rings, reddish-brown in the center and surrounded by a yellowish-green halo, as a typical symptom of target spot. Reddish-brown lesions on the roots and stem of the seedlings were also observed. Considering a sample seed with 66.0% of C. cassiicola incidence, the symptomatic transmission based on cotyledon symptoms was 42.2%, corresponding to a transmission rate of 2.4:1. This is the first report, in a quantified way, about the transmission of C. cassiicola from the seeds to above-ground parts of soybean seedlings. When compared to non-inoculated seeds, seed germination, seedling emergence, and seedling initial development were influenced by the presence of the pathogen in the seeds, with the lowest values being observed when the seeds were inoculated.
O fungo Corynespora cassiicola, agente causal da mancha alvo da soja, tem sido considerado, do ponto de vista da patologia de sementes, um patógeno de importância limitada. Por esse motivo, pouca importância foi dada em relação ao papel das sementes na transmissão desse patógeno. Os objetivos desse trabalho foram determinar a incidência de C. cassiicola em sementes de soja bem como avaliar os efeitos da presença desse patógeno, inoculado nas sementes, com parâmetros fisiológicos e epidemiológicos. Os experimentos foram conduzidas na TAGRO e na Embrapa Agropecuária Oeste e constaram de testes de laboratório (blotter test e teste padrão de germinação) e de casa de vegetação (growing on test). O fungo C. cassiicola foi detectado em 11,3% das 639 amostras de sementes analisadas, com incidência média de 0,91% e a máxima de 8,5%. A transmissão de C. cassiicola, da semente para a parte aérea das plântulas de soja foi demonstrada, pelo estabelecimento do patógeno nos cotilédones, apresentando lesões circulares com anéis concêntricos, marrom-avermelhada no centro e com presença de halos amarelados, característicos da mancha alvo. Lesões radiculares e no colo das plântulas, de coloração marrom avermelhada, também foram observadas. Considerando a incidência de C. cassiicola na semente de 66,0%, a transmissão sintomática do fungo baseada em sintomas no cotilédone, foi de 42,2%, o que representou uma taxa de transmissão de 2,4:1. Esse é o primeiro relato, de forma quantificada, da transmissão de C. cassiicola das sementes para a parte aérea das plântulas de soja. Em comparação às sementes não inoculadas, a germinação das sementes, emergência e o desenvolvimento inicial das plântulas foram influenciados pela presença do patógeno nas sementes, com os menores valores sendo observados quando as sementes foram inoculadas.
Subject(s)
Seeds/microbiology , Glycine max , Fungi/pathogenicityABSTRACT
Corynespora cassiicola is a cosmopolitan ascomycete widely known as phytopathogen in several crops, and more recently as an emerging pathogen in humans. In this study the genetic variability of 60 isolates of Corynespora cassiicola from different hosts and cities of Amazonas was evaluated, using AFLP molecular markers. Seven genetic groups were identified according to a dendrogram obtained by the Unweighted Pair Group Method using Arithmetical Averages, indicating significant variability among the isolates. Three isolates of different hosts (28, obtained from papaya; 55, obtained from cucumber; and 58, from tomato) remained as single individuals in distinct groups, suggesting marked genetic variation in comparison to the other isolates and possible specificity by the host.(AU)
Corynespora cassiicola é um ascomiceto cosmopolita amplamente conhecido como fitopatógeno em diversas culturas e, mais recentemente, como patógeno emergente em humanos. Na região Norte do Brasil é responsável por perdas significativas em cultivos tanto em casa de vegetação como em campo aberto. Neste estudo foi avaliada a variabilidade genética de 60 isolados de Corynespora cassiicola procedentes de diferentes hospedeiras e municípios do Amazonas, usando marcadores moleculares AFLP. Foram identificados sete grupos genéticos de acordo com dendrograma obtido pelo método de agrupamento UPGMA, indicando significativa variabilidade entre os isolados. Três isolados de diferentes hospedeiras (isolado 28, obtido de mamoeiro; isolado 55, obtido de pepineiro; e isolado 58, proveniente de tomateiro) permaneceram como indivíduos únicos em grupos distintos, sugerindo variação genética marcante em comparação com os demais e possível especificidade pela hospedeira de origem.(AU)
Subject(s)
Fungi/pathogenicity , Noxae , Plant Diseases , Biological Variation, PopulationABSTRACT
As a local parasitic disease in Qinghai,Tibet,Xinjiang and other places,cerebral hydatid disease has high morbidity and mortality.At present,the main drug for Echinococcosis is benzimidazole.However,due to the lack of efficacy and side effects of these drugs,we urgently need to develop new drugs.In this paper,we gives a brief introduction of the application of genomics,stem cells and signaling pathway knowledge in developing new drugs of hydatid,which aims to understand the limitations of current hydatid medication,summarize the research progress of new drugs,put forward the potential research direction,prompting the development of new drug research.
ABSTRACT
Objective: To identify the pathogen of Menispermum dauricum target spot (a new plant disease in China) and study its biological characteristics and susceptibility to fungicides. Methods: Tissue isolation method was used to obtain the isolates from diseased-leaf. The pathoginicity of the isolates was fulfilled according to Koch's postulate. The identification of the pathogen was carried out according to the morphological and cultural characteristics and rDNA-ITS sequence analysis. The effects of culture medium, temperature, pH value, carbon and nitrogen sources, and light on mycelium growth and sclerotia production of the pathogen were studied. The mycelium growth rate was used to test the susceptibility of pathogen for 14 fungicides. Results: The M. dauricum target spot was caused by Streptobotrys caulophylli. The optimal medium for mycelium growth was PDA; PDA and PSA media were suitable for the sclerotium production. The optimal temperature ranges for mycelium growth and spore production were 20-28℃ and 10-30℃ and were suitable for sclerotium production. The suitable pH values for mycelium growth and sclerotium production were 4-9 and 5-11, respectively. Sucrose and L-glutamine were the optimal carbon and nitrogen sources for mycelium growth. Synanthrin and sucrose were the optimal carbon source and sodium nitrate was nitrogen source for sclerotium production. The total light could promote mycelium growth, while the darkness could promote sclerotium production. The pathogen was sensitive to procymidone, cyprodinil, iprodione, fludioxonil, metalaxyl•mancozeb, and pyraclostrobin•metiram with EC50 < 1.0 mg/L and EC90 < 5.0 mg/L. Conclusion: It is the first report on M. dauricum target spot caused by S. caulophylli in China. The suitable conditions (culture medium, temperature, pH value, carbon and nitrogen sources, and light) for mycilium growth and sclerotium production are determined. The above six fungicides are screened as further field trial agents for disease control.