Caracterização fisiológica de isolados de Corynespora cassiicola

Abstract

RESUMOCorynespora cassiicola, agente causal da mancha alvo, causa prejuízos econômicos em diversas culturas. Como a disponibilidade de protocolos padronizados para a produção de inóculo facilitam a condução de testes de patogenicidade, os objetivos deste trabalho foram analisar o crescimento micelial em diferentes temperaturas; avaliar o crescimento micelial e a esporulação de isolados obtidos de diferentes hospedeiros em diferentes regimes de luz; avaliar o efeito da duração de umidade contínua para a máxima germinação dos esporos in vitro e a patogenicidade de sete isolados de C. cassiicola em diversos hospedeiros. As temperaturas para o maior crescimento micelial variaram de 23,3 a 29,5ºC; o crescimento de oito isolados foi indiferente aos regimes de luz, enquanto os outros seis foram mais influenciados pelo escuro contínuo; a maioria dos isolados esporulou mais sob luz contínua; cinco a vinte horas de umidade contínua foi a variação de tempo para que 85% dos esporos germinassem; quanto à patogenicidade, foi observado que o algodoeiro, o meloeiro e o pepineiro foram os hospedeiros mais suscetíveis, e menos suscetíveis, o tomateiro, aceroleira e o cafeeiro. Para produção massal de inóculo de C. cassiicola recomenda-se utilizar a temperatura de 25ºC sob luz contínua. Palavras-chave: esporulação, fotoperíodo, germinação de esporos, inoculação cruzada, patogenicidade. ABSTRACT Physiological characterization of Corynespora cassiicola isolatesCorynespora cassiicola is the causal agent of target spot on several crops of economic importance. Since the availability of standardized protocols for inoculum production makes the conduction of patogenicity tests easier, the objectives of this work were to evaluate the mycelial growth under different temperatures, to evaluate the mycelial growth and spore production under different photoperiods for isolates obtained from different hosts, to evaluate the effect of continuous humidity on spore germination, and the pathogenicity of seven isolates of C. cassiicola on several hosts. Temperatures between 23,3 and 29,5ºC allowed the best growth of the isolates. The growth of eight isolates did not respond to the photoperiods used whereas six isolates were sensitive to the dark. The best sporulation for the majority of isolates was under continuous light. Five to twenty hours of continuous humidity were enough for 85% of the spores to germinate. As for pathogenicity, cotton, melon and cucumber were the most susceptible hosts, while tomato, coffee and Antilles cherry were the least susceptible. For massal production of C. cassiicola inoculum, a temperature of 25ºC under continual light is recommended.

Yield losses of soybean due to target spot (<i>Corynespora cassiicola</i>), its genetic and chemical management

“…Our results did not agree with the observed by Teramoto et al, (2013a) that reported significant interaction for six Brazilian C. cassiicola isolates and twelve soybean cultivars in a single assessment of disease severity. The high variability reported for the fungus aggressiveness Teramoto et al, 2013b) and in the host resistance did not implied an interaction effect for the present experimental conditions.…”

In vitro susceptibility of Corynespora cassiicola isolate from Brazil fields to fungicide

“…It is known that the abuse of systemic molecules to control pathogens causes reduction in the sensitivity to products (Reis et al, 2010). In some studies, the fungicide carbendazim had low efficiency in controlling the target spot, which could have been as a result of the resistance to this chemical group on the pathogen (Teramoto et al, 2013;Avozani et al, 2014). However, in this work, carbendazim fungicide did not appear to be inefficient in its toxicity.…”

Control químico del manchado de hojas y cálices de jamaica en Guerrero, México

“…En los ciclos productivos de 2014 y 2015 para Ayutla y Tecoanapa, las temperaturas promedio oscilaron entre 25.01 °C y 28.24 °C con humedades relativas entre 71.46% y 95.67% (Tabla 3). En base a lo reportado por Teramoto et al (17), mencionan que las temperaturas entre 23.3 °C a 29.5 °C y alta humedad relativa (100%) (2) son favorables para C. cassiicola, condiciones similares fueron registradas en el presente estudio (Tabla 3).…”