Morphological and molecular characterization of Macrophomina phaseolina isolated from three legume crops and evaluation of mungbean genotypes for resistance to dry root rot

Abstract

Dry root rot (DRR) is an important emerging disease of mungbean caused by fungus Macrophomina phaseolina. The disease is seed and soil-borne and hence management is difficult. Exploitation of host resistance could be a good option to manage the disease. The objectives of this study were to characterize the isolates of M. phaseolina from three legume crops and to identify resistant sources against DRR of mungbean. Isolates of M. phaseolina from mungbean, urdbean, and vegetable soybean were identified using morphological characteristics and sequencing internal transcribed sequence (ITS) region of 18S rRNA. Isolates of M. phaseolina from urdbean and vegetable soybean were inoculated on susceptible check genotype of mungbean to assess their pathogenicity. Forty three mungbean genotypes were screened against M. phaseolina isolate of mungbean using the paper towel method to identify sources of resistance. Among these genotypes, 9 were resistant in repeated experiment, with disease score ranging from 1.9 to 3.0. Resistant genotypes showing lower disease score, namely IPM99-125, EC693368, and EC693369, were further screened using the sick pot method to confirm their resistance. Among these three genotypes, IPM99-125 showed consistently higher plant survival rate followed by EC693368 and EC693369 as compared to susceptible checks (VC3960-88, KPS1). In addition, these three genotypes were resistant when screened with two strains of M. phaseolina isolated from urdbean and vegetable soybean, with IPM99-125 having lower disease score. The mungbean genotype IPM99-125 could be useful in mungbean breeding programs to develop root rot-resistant varieties.