STUDIES ON YELLOW MOSAIC DISEASE OF MAJOR GOURDS
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Date
2021-12-18
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Keladi Shivappa Nayaka University of Agricultural & Horticultural Sciences, Shivamogga
Abstract
Yellow mosaic disease (YMD) in ridge gourd, bitter gourd, ivy gourd and bottle gourd caused by tomato leaf curl New Delhi virus (ToLCNDV) was an economically important disease which hampered the crop growth and yield. ToLCNDV is a begomovirus that was persistently transmitted by whitefly (Bemisia tabaci). Among major diseases occurring on gourds, YMD was one of the most prevalent and serious problem in Karnataka. Roving survey was conducted during summer 2020-21 to assess the incidence of YMD in Chikmagalur, Davangere and Shivamogga districts. Survey results revealed that the highest disease incidence of 58.18 per cent in ridge gourd, 59.21 per cent in bitter gourd, 32.50 per cent in ivy gourd and 42.50 per cent in bottle gourd were documented. Among the district surveyed, Davanagere district has recorded the highest mean disease incidence of YMD in all the gourds. Suspected YMD infected samples collected during surveyed areas were tested by PCR using begomovirus specific primers for conserved region, Rep associated protein and coat protein gene. The PCR product of 560bp and 1200bp was obtained, respectively. The nucleotide sequences of replication associated protein and coat protein gene of YMD infected ridge gourd, bitter gourd, ivy gourd and bottle gourd showed 99.72, 98.94, 99.00 and 100 per cent identity with ToLCNDV, respectively. Phylogenetic analysis of Rep associated protein and coat protein gene sequences of ToLCNDV isolates of ridge gourd, bitter gourd and ivy gourd formed a single cluster, while bottle gourd formed a separate cluster. Ridge gourd yellow mosaic virus (strain of ToLCNDV) has been successfully transmitted by whiteflies (Bemisia tabaci). Inoculating 10 adult whiteflies per plant with 12h of acquisition access period (AAP) and inoculation access period (IAP) resulted in 100 per cent virus transmission. The virus transmitted in persistant manner and retained in whiteflies for 5-8 days.