Identification of new sources of resistance to dry root rot caused by Macrophomina phaseolina isolates from India and Myanmar in a mungbean mini-core collection

Abstract

Dry root rot (DRR), caused by Macrophomina phaseolina, is a prevalent disease of mungbean in Myanmar, and an emerging problem in South Asia. The pathogen is a polyphagous necrotroph, survives in the soil for many years that results disease mitigation difficult. Managing DRR in mungbean through an integrated approach has been suggested, and the use of resistant varieties is one of the economical methods. The present study aimed to identify sources of resistance against DRR from a mungbean mini-core collection and to characterize the associated M. phaseolina isolates from India and Myanmar. Evaluation of the 296 mungbean mini-core accessions against the isolate MP1 by paper towel method identified 29 accessions with DRR resistance (disease scores: ≤ 3), and 18 of them with the consistent resistance in the repeated experiment. During the screening of 18 resistant accessions in the glasshouse, nine accessions were found DRR resistance in repeated sick pot experiments with ≤10% disease incidence. A subset of 30 accessions was selected from the mini-core collection based on their in vitro DRR reactions. These accessions were evaluated for DRR resistance in the field in Yezin, Myanmar in 2018 and 2019. Out of the 30 accessions, ten accessions were found DRR resistance with ≤10% disease incidence in both years of evaluations. Pooled analysis of percent disease incidence data of 15 accessions common in both glasshouse and field revealed the stability of accessions VI001509AG, VI001244AG, and VI001400AG for DRR resistance across years and locations. The three resistant accessions along with a susceptible check VC693088 were re-evaluated by paper towel method against nine additional M. phaseolina isolates from India (MP3-MP11). The accessions VI001509AG and VI001400AG were resistant to all nine isolates, while accession VI001244AG was resistant to MP5, MP6, and MP7 isolates. These accessions could be used in mungbean DRR resistance breeding programs.