INFLUENCE OF RELATIVE-HUMIDITY AND TEMPERATURE ON DEVELOPMENT OF DIDYMELLA-RABIEI ON CHICKPEA DEBRIS

Didymella rabiei grew saprophytically on pieces of artificially and na turally infected chickpea stem debris under artificial incubation cond itions, and formed pseudothecia and pycnidia. The extent of growth was not significantly affected by temperature of incubation within the ra nge 5-25 degrees C, but was significantly reduced as relative humidity (RH) decreased from 100% to 86%, when no growth occurred. Pseudotheci a matured at 10 degrees C and constant 100% RH, or at 5 and 10 degrees C and alternating 100%/34% RH. Under these conditions, pseudothecial maturation, assessed by a pseudothecia maturity index, increased over time according to the logistic model. For temperatures higher than 10 degrees C or RH lower than 100%, pseudothecia either did not form asco spores, or ascopores did not mature and their content degenerated. Whe n pseudothecia that initially developed to a given developmental stage were further incubated at a constant 100% RH, temperature became less limiting for complete pseudothecial development as the developmental stage was more advanced. Pycnidia of the fungus developed and formed v iable conidia in all environmental conditions studied, except at 86% R H. However, the density of pycnidia formed and the number of viable co nidia per pycnidium were significantly influenced by temperature, RH a nd the type of debris (artificially or naturally infected) used.