Variability and Integrated Management of Stem and Root Rot of Cowpea Caused by Macrophomina phaseolina Tassi Goid

Abstract

Cowpea is short duration multipurpose pulse crop grown extensively in tropical newlineand subtropical countries. Stem and root rot incited by M. phaseolina is an emerging newlineand most devastating disease, which causes significant yield loss in major cowpea newlinegrowing areas of Karnataka. Among the surveyed districts from rabi-summer 2021-22 newlineand 2022-23, Koppal recorded maximum disease incidence of 32.76 per cent followed newlineby Gadag district (31.20 %) whereas, Belagavi district recorded least disease incidence newlineof 22.47 per cent. In taluk wise analysis, irrespective of both the years, Kushtagi taluk newlineof Koppal district recorded maximum disease incidence of 39.58 per cent followed by newlineLakshmeshwar taluk of Gadag district (34.03 %). The disease caused an estimated grain newlineyield loss of 19.64 - 43.74 per cent in 10 genotypes. The moderately resistant genotype newlineKBC 9 had the lowest grain yield loss (19.64 %), while the susceptible genotype C 152 newlinehad high yield loss of up to 43.74 per cent. newlineTwenty-three isolates of M. phaseolina collected during survey were studied for newlinemorphological and molecular diversity. All the isolates differed morphologically with newlinerespect to mycelial growth (slow, medium, fast), mycelial colour (white, whitish grey, newlineblackish grey, black), growth pattern (fluffy, profusely fluffy, flat), dry mycelial weight newline(low, medium, high), sclerotial size (small, medium, high), sclerotial shape (Globose, newlineoblong, irregular) and pycnidia formation. Twenty isolates were analyzed for molecular newlinevariability through species specific calmodulin (CAL) and translation elongation factor newline1-alpha (TEF1-and#945;) primers. All the isolates showed amplicon at 403 bp and 217 bp for newlineCAL and TEF1-and#945; primers, respectively. The phylogenetic tree constructed using newlinecombined CAL and TEF1-and#945; gene sequences revealed the three major clusters, with 12 newlineisolates in cluster I, four isolates in cluster II and four isolates in cluster III. Further newlinegenetic diversity analysis using inter-simple sequence repeat (ISSR) markers, showed newlinepolymorphic and distinguishable banding pa