Diversity analysis of Pseudocercospora griseola populations causing angular leaf spot of common bean and identification of resistant sources

Abstract

The present investigation entitled Diversity analysis of Pseudocercospora griseola populations causing angular leaf newlinespot of common bean and identification of resistant sources was undertaken during 2019-2023 to identify pathogen, newlinestandardization of culture technique, variability in P. griseola and evaluation of common bean germplasm for newlineresistance sources. Angular leaf spot of common bean caused by Pseudocercospora griseola emerged as most newlinedestructive disease in Himachal Pradesh as 21.3 to 76.2 per cent disease severity was observed. Fifty isolates of P. newlinegriseola were collected from different locations of six districts (Chamba, Kangra, Kullu, Kinnaur, Mandi and Shimla) newlinerepresenting three agro-climatic zones of Himachal Pradesh. Isolations were done by using four different methods newlineviz., by infected leaf bits, sterilized toothpick, moist chamber method and by picking up synnemata from diseased newlineleaves. Out of these methods, picking up synnemata from infected leaves was found most efficient with 58.0 per cent newlinerecovery efficiency. Total 40 isolates were recovered by using different isolation methods. These isolates were newlineidentified as Pseudocercospora griseola based on morpho-cultural characters and were confirmed further with newlinemolecular techniques. Among culture techniques, V8 juice agar medium at 24oC temperature with pH level 6 and newlinerelative humidity levels of 85 to 90 per cent supported the maximum mycelial growth and sporulation. The pathogen newlinewas found variable on the basis of morpho-cultural characteristics and isolates were categorized into 8 groups i.e. newlinePG-MV1-PG-MV8. The virulence structure and pattern of 40 isolates was studied on 9 differential lines and on basis newlineof pathotype designation, P. griseola isolates were grouped into 5 pathotypes i.e. PPG1-PPG5. Among 5 pathotypes newlinePPG1 was found highly virulent which gave susceptible reaction on 8 out of 9 differential lines used whereas PPG5 newlinewas least virulent which gave susceptible reaction against only 3 differential lines. PPG4 pathotype was fo