STUDIES ON VIRAL DISEASES OF URDBEAN [Vigna mungo (L.) HEPPER]
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The investigation on the “Studies on viral diseases of urdbean [Vigna mungo (L.) Hepper] was carried out at Agricultural College, Bapatla, Guntur district, Andhra Pradesh during 2013-14.
Survey conducted in Guntur district of Andhra Pradesh during rabi 2013-14 revealed the incidence and severity of mungbean yellow mosaic disease caused by MYMV in the range of 4-36% and 1.78-38.22%, respectively. Per cent incidence of leaf curl disease caused by GBNV and leaf crinkle disease caused by urdbean leaf crinkle virus were in the range of 6-18% and 11-25%, respectively. DAC-ELISA tests of leaf curl infected samples confirmed the prevalence of GBNV.
Mungbean yellow mosaic disease symptoms appeared as yellow diffused spots scattered on leaf lamina and rapidly expanded. Very soon, each leaf showed yellow patches alternating with green colour. The affected leaves were reduced in size and later turned completely yellow. Leaves with severe symptoms turned necrotic.
Leaf curl disease showed veinal discoloration. These veins later became necrotic resulting in downward curling of leaves. On the surface of the infected leaves, chlorotic lesions turning necrotic were observed. Leaf necrosis lead to the death of growing bud. Early infection caused the death of the plant.
Urdbean leaf crinkle virus caused systemic infection in blackgram. The characteristic symptoms associated with the disease were puckering, crinkling and curling of leaves, reduction in petiole length, malformation of flowers and stunted growth.
Mechanical sap inoculation of cowpea cv. C-152 with GBNV infected leaf sample produced chlorotic lesions five to seven days after inoculation which later turned necrotic. ULCV sap inoculation on blackgram (LBG 623) produced disease symptoms eight to ten days after inoculation, inoculated leaves showed upward curling, foamy texture, pale green, severe crinkling and were reduced in size compared to normal leaves.
During kharif 2013, MYMV incidence revealed a significant positive correlation with relative humidity (8:30 AM) and evening relative humidity (5:30 PM) whereas during rabi 2013-14, whitefly population per trifoliate leaf, maximum temperature and minimum temperature showed positive significant correlation, relative humidity at 8:30 AM showed significant negative correlation. Leaf curl incidence showed positive significant correlation with relative humidity at 8:30 AM and relative humidity at 5:30 PM during kharif 2013 whereas maximum temperature and minimum temperature showed significant positive correlation, relative humidity at 8:30 AM showed significant negative correlation during rabi 2013-14. Leaf crinkle incidence showed positive significant correlation with relative humidity at 5:30 PM during kharif 2013 whereas during rabi leaf crinkle incidence had significant positive correlation with maximum and minimum temp and significant negative correlation with relative humidity at 8:30 AM.
Eighty-five genotypes of urdbean screened against virus diseases under field conditions with LBG 623 as susceptible check showed varied per cent incidence. Seventy-three genotypes showed resistant reaction whereas eight genotypes were moderately resistant to MYMV, three genotypes were immune and 18 genotypes were highly resistant to leaf curl disease. Thirty-seven genotypes were immune and 28 were highly resistant to ULCV while all other genotypes showed moderately resistant to immune reaction. 91.7% of MYMV resistant, 70.58% of leaf curl resistant and 94.5 %, of leaf crinkle immune genotypes exhibited dense pubescence. MYMV resistant genotypes, leaf curl resistant genotypes and leaf crinkle immune genotypes showed highest wax content in the range of 0.417 to 0.653 mg dm-2.
Seed treatment with imidacloprid @ 5g/kg seed and insecticidal spray with thiamethoxam @ 0.2 g / l at 30 DAS resulted in significant control of virus diseases through vector control. It also improved shoot length, number of primary branches per plant, number of pods per plant, 100 seed weight, seed yield and it was found economical.
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D5195
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