ABSTRACT

A fixed plot survey conducted during summer 2023-24 at different locations of Northern Karnataka, revealed that, maximum disease incidence of horsegram YMD was recorded in ARS, Bailhongal (48.72 %), followed by RARS, Vijayapura (40.18 %), MARS, Dharwad (35.98 %) and ARS, Bagalkot (20.47 %). Population dynamics conducted at MARS, revealed that, mean whitefly population peaked during 10th and 11th SMWs. Population buildup showed significant positive correlation with maximum and minimum temperature and sunshine duration and significant negative correlation with maximum and minimum RH and rainfall. Loss assessment revealed that, among all genotypes PHG-9 showed least yield loss (17.35 %) with less incidence (21.62 %) and VHG-44 showed highest yield loss (31.10 %) with high incidence (58.67 %). DNA fragments of ~896 bp (PQ230896.1) and ~876 bp (PQ179272.1) were obtained from infected horsegram leaf sample by using HgYMV specific CP gene primers. Sequence analysis revealed that the CP gene of HgYMV isolate 1 (PQ230896.1) and 2 (PQ179272.1) shared highest (96.79 % and 98.74 %, respectively) similarity with HgYMV Dharwad isolate (MN602423.1) at nucleotide level. Similarity analysis indicated that isolate causing YMD in horsegram at Dharwad was HgYMV.
Management of YMD revealed that, seed treatment with imidacloprid 600 FS at 5ml/kg of seeds and spray with pyriproxyfen 5%+diafenthiuron 25% (30% SE) at 2 ml/1 at 30, 45 and 60 DAS resulted in the lowest incidence and highest reduction of whitefly population with seed yield of 6.91 q/ha and B:C ratio of 1.69. Among 148 genotypes screened against YMD, twelve lines were moderately resistant (14-61-41, CRHG-9, GPM-15, GPM-17, VLG-8, GPM-36a, PHG-2a, PHG-9, TCR-1517b, TCR-1734b, TRR-1799 and TCR-1816), forty-seven lines were moderately susceptible, forty-six lines were susceptible and forty-three lines were highly susceptible. Identified moderately resistant genotypes can be utilized in YMD resistance breeding programme to develop YMD resistant varieties.