Analyses of genetic and pathogenic variability among Botrytis cinerea isolates

Seventy nine isolates of Botrytis cinerea were collected from different host plants and different locations of India and Nepal. All the isolates were identified as B. cinerea based on morphological features and were confirmed using B. cinerea specific primers. Differentiation among the isolates was assessed using morphological, genetic and biochemical approaches. To analyze morphological variability, differences in conidial size, presence or absence of sclerotia and their arrangement were observed. Genetic variability was characterized using RAPD analysis, presence or absence of transposons and mating type genes. Cluster analysis based on RAPD markers was used for defining groups on the basis of geographical region and host. The biochemical approach included determining differences in concentration of oxalic acid and activity of lytic enzymes. All the isolates were categorized into different pathogenic groups on the basis their variable reaction towards chickpea plants. Isolates with higher concentration of oxalic acid and greater activity of lytic enzymes were generally more pathogenic. Pathogenicity was also correlated to transposons. Isolates containing transposa group showed some degree of correlation with pathogenic behavior. However, isolates could not be grouped on the basis of a single approach which provides evidence of their wide diversity and high evolution potential. Sensitivity of sampled isolates was also tested against five botryticides. Most of the isolates from same region were inhibited by a particular fungicide. This feature provided interesting cues and would assist in devising novel and more effective measures for managing the disease.