Vol. 11, Issue 12 (2022)

Pathogenicity of A. alternata 15 isolates was attempted, using Alternaria blight susceptible groundnut Local cultivar and spray inoculating the mycelium-cum –spore suspension separately of the test isolates, in screen house clearly indicated that all the 15 isolates of A. alternata exhibited a wide range of pathogenic variability. However, the aggressive isolates viz., AaDp, AaSg and AaKd were found to be highly virulent, with least incubation period (7 to 8 day), highest lesion frequency (17.00 to 19.00/plant), large sized leaf spots (11.33 to 12.83 mm²), highest per cent disease incidence (42.33 to 53.29%) and severity (40.42 to 45.17%). Whereas, moderately virulent/aggressive isolates exhibited moderate incubation period (10 to 11 days), moderate lesion frequency (10.00 to 12.89/plant), medium sized spots (4.38 to 9.92 mm²), moderate disease incidence (16.88 to 34.51%) and disease severity (13.56 to 31.27%); and the least virulent/aggressive isolates exhibited maximum incubation period (13 to 14 days), least lesion frequency (8.50 to 10.66/plant), small sized spots (3.66 to 5.63 mm²), least disease incidence (12.77 to 18.49%) and disease severity (13.45 to 15.33%).