Cultural, Morphological Characterization and Aggressiveness of Alternaria alternata Causing Leaf Spot of Soybean

Abstract

Background: Alternaria leaf spot caused by Alternaria alternata is one of the most important and destructive disease of soybean causing severe yield loss in all soybean growing areas of southern and eastern part of Rajasthan. Successful management of Alternaria leaf spot is mainly dependent on accurate and efficient detection of pathogen, amount of genetic and pathogenic variability present in pathogen population. The main reason for frequent “breakdown” of effective resistance is the variability that exists in the pathogen population, which necessitates a continual replacement of cultivars due to disease susceptibility. Methods: The twelve fungal isolates randomly were collected from six districts of major soybean growing part of Rajasthan i.e., Udaipur, Chittorgarh, Pratapgarh, Kota, Baran and Jhalawar. The culture was purified single spore techniques. These were then further compared among each other for any variations in cultural characters, colour of colonies, Growth rate, conidial morphology and pathogenic variability. Result: Twelve different isolates of A. alternata were obtained in pure culture and characterized for cultural, morphological variation and aggressiveness of this fungus varied in their cultural characters, colour of colonies, growth rate of isolates, conidial morphology and isolates also exhibited variations in incubation period, latent period, number and size of lesions were produced.