Morpho-molecular characterisation of angular leaf spot pathogen and identification of new sources of resistance in North-western Himalayan common beans

Angular leaf spot (ALS) is one of the most catastrophic diseases limiting the production of common bean ( Phaseolus vulgaris L.). This study was conducted to characterize common bean angular leaf spot pathogen based on morphology and internal transcribed spacer (ITS) region, and to identify the sources of resistance. Two isolates Pg01 and Pg02 were identified as Pseudocercospora griseola based on morphological characteristics . In order to decipher the formae to which these isolates belong, internal transcribed spacer (ITS) regions of rDNA of two isolates were sequenced and the sequences with accession numbers MZ452242 and MZ413342 showed maximum similarity with the Andean types i.e. Pseudocercospora griseola f.sp. griseola sequences available at NCBI. In phylogenetic analysis, isolates Pg01 and Pg02 were clustered with P. griseola f.sp. griseola (Andean types) sequences retrieved from GenBank, whereas the sequences of P. griseola f.sp. mesoamericana were clustered separately. For germplasm evaluation under field conditions in the year 2020, out of 85 different genotypes 21 genotypes were resistant, 49 genotypes showed intermediate reaction and 15 genotypes were susceptible and in 2021, 25 genotypes showed resistant reaction, 47 genotypes were found intermediate, and 13 genotypes were found susceptible. Among 54 genotypes screened in greenhouse under artificial inoculation with Andean race Pg02 in 2020, 11 genotypes were resistant, 13 genotypes showed intermediate reaction while as rest of the genotypes were susceptible.