Survey, cultural and morphological studies of Alternaria leaf spot of cotton incited by Alternaria alternata

Abstract

Cotton is one of the most important commercial crops in India and world. Cotton constitutes approximately 59% of the Indian textile industry's raw material consumption basket. Annual cotton consumption exceeds 300 million bales (170 kg each). The roving survey was conducted in 9 blocks of Khargone district of madhyapradesh (India) in Kharif season (2022-23), Collected data of percent disease incidence (PDI) of Alternaria leaf spot on cotton. Observation was recorded from different villages under natural field conditions. The average Percent disease incidence of Khargone district was 24.65% and it ranged from 17.6 to 32.9%. The mean maximum disease incidence was recorded in Bhikangaon (32.9%) followed by Kasrawad (29.10%), Jhirniya (27.96%), Maheshwar (25.60%) and Segaon (25.18%), While lowest average disease incidence was noticed in Gogawan (17.62%). Alternaria alternate is responsible pathogen for Alternaria leaf spot of cotton and which is highly variable pathogen. Cultural characters of pathogen (Alternaria alternata) were studied on the PDA media.Isolate CAM-3 and CAM-6 belongs to Category-I, which has Greyish White colour of colony while CAM-1, CAM-2, CAM-5 and CAM-7 belongs to category-II, which has White colour of colony and CAM-4, CAM-8 and CAM-9 belongs to category-II, which has Greyish Black colour of colony. Overall length of conidia ranged between 33-65 μm, while width at broadest part of conidia ranged between 5-12 μm and beak of 4-10 μm., the highest observed in CAM-9 (65 x 12 μm), followed by CAM-8 (63 × 10 μm), while minimum size of conidia was CAM-7 (33 × 5 μm).