Screening and Identification of Blackgram Genotypes Resistant to Mungbean Yellow Mosaic Virus Disease

Mungbean yellow mosaic virus (MYMV), transmitted by the whitefly (Bemisia tabaci), is a major biotic constraint limiting yield and seed quality of blackgram (Vigna mungo). To identify field-resistant donor sources, a screening study was conducted under natural epidemic conditions at the Regional Agricultural Research Station, Lam, Guntur, Andhra Pradesh, India, during summer 2018 and kharif 2019. Fifty-nine blackgram genotypes along with four checks were evaluated using an Augmented Completely Randomized Block Design (ACRBD)-II and an infector-row technique, with no insecticide application to allow natural vector build-up and disease spread. Standard agronomic practices were followed to ensure uniform crop growth. Disease incidence and symptom severity were recorded on five randomly selected plants per entry at the stage when widespread symptoms were evident in the susceptible check, and each entry was rated using a 1–9 disease scoring scale. Based on mean score, genotypes were grouped into reaction classes as resistant (1.0–2.0), moderately resistant (2.1–4.0), moderately susceptible (4.1–5.0), susceptible (5.1–7.0), and highly susceptible (7.1–9.0). Across the two seasons, 51 genotypes were classified as resistant, 4 as moderately resistant, 1 as moderately susceptible, 2 as susceptible, and 1 as highly susceptible. The most promising resistant lines included IPU 17-02, LBG 904, Uttara, TU 94-2, OBG 101, OBG 102, LBG 918, KUG 818, TBG 129, and LBG 972, which consistently expressed minimal symptoms and low infection levels. These genotypes can serve as potential donor parents for resistance breeding and as candidates for further multi-location validation to develop stable MYMV-resistant blackgram cultivars.