Study of Morpho-physiological and Biochemical Traits for Resistance to Yellow Mosaic Virus (YMV) in Blackgram [Vigna mungo (L.) Hepper] Varieties

Background: Blackgram is one of the most important pulse crop in India and it is being affected by a number of insect pests from seedling stage to maturity. Among them whitefly is an important insect pest that transmit the viral disease, yellow mosaic virus (YMV), which is a major disease resulting in severe yield losses accounting for about 70% and infection at early stages may result in complete failure of the crop causing huge loss to the farmers economically. To overcome the losses due to this important disease in blackgram, study of host plant resistance to whiteflies, thereby minimizing the losses due to YMV disease is of great importance. The trichome density plays an important role as a morphological anti-feedant which reduces the pest attack and subsequently lowers the disease incidence and the plants with high trichome density showed less YMV symptom. The morpho-physiological and biochemical traits play an important role in host plant resistance against YMV disease through insect vector resistance and hence, the study was undertaken. Mathods: A field experiment was conducted during rabi 2017-18 and 2018-19 at RARS, Lam, Guntur in a randomized block design with eight blackgram varieties and replicated thrice under receding soil moisture condition. The experiment was conducted using eight blackgram varieties (LBG 787, GBG 1, TBG 104, LBG 884, LBG 806, LBG 808, LBG 623 and LBG 752) obtained from RARS Lam, Guntur and the variety LBG 623 was considered as a susceptible check. The estimation of sugars, phenols, tannins, trichome density and SCMR was done at vegetative and reproductive stages of crop growth. Result: A significant variation was observed among the varieties for all the traits observed at vegetative and reproductive growth stages during both rabi 2017-18 and 2018-19. The total sugar content of the blackgram varieties varied from 25.16 to 49.82 mgg-1 FW; the leaf phenolic content values ranged from 10.26 to 23.55 mg g-1 FW and the tannins content of the dried leaf samples ranged from 0.014 to 0.052 mgg-1 DW. The trichome density of the blackgram varieties varied from 12.91 to 74.59/cm2 of leaf area and the SCMR values ranged from 24.21 to 55.17. Higher seed yield was recorded in the variety LBG 884 followed by GBG1 and the lower seed yield was recorded in the variety LBG 623 during rabi 2017-18 and 2018-19. The YMV resistant varieties showed relatively higher phenolic, tannins content and trichome density and lower total sugar content in the leaf. The total sugar content showed a significant negative correlation with the seed yield. The SCMR value was significantly lower in the susceptible varieties of blackgram with higher disease scores.