Title : Characterization of begomovirus associated with yellow mosaic disease of ridge gourd Luffa acutangula (L) Roxb
Abstract:
Ridge Gourd [Luffa acutangula (L.) Roxb.] It is commercial crop in the south and east India and commonly grown all over India particularly in states like Andhra Pradesh, Tamil Nadu, Gujarat, Konkan region of Maharashtra, Assam, West Bengal and Karnataka. It gives good yields up to 100-200 quintal per hectare and fetching good returns. This crop is known to get affected by many diseases. But in recently yellow mosaic disease on ridge gourd reported in southern states of India. It seems to be a newly emerged disease particularly in hot season. Roving survey in southern states of major ridge gourd growing areas during March to April 2015 revealed that disease incidence ranged from 30-100 per cent. A total of 63 samples out of 66 samples collected during surveys were found detected for both DNA-A and DNA-B components of begomovirus indicating that all detected samples were associated with bipartite begomovirus. PCR analysis of surveyed samples with beta and alpha-DNA satellites specific primers revealed that absence of both satellite DNAs in all the samples. Representative surveyed sample was subjected to molecular characterization by sequencing the complete genome of the virus. The isolate has both DNA-A and DNA-B components. The DNA-A component consisted of 2,739 nt and DNA-B of 2,693 nt, which was approximately similar to other begomoviruses (ToLCNDV). Phylogenetic analysis of complete nucleotide sequence of both DNA-A and DNA-B of ToLCNDV-[IN:Kar:Bgk:Rid:15] with other selected begomoviruses showed the clustering of virus with ToLCNDV isolates and formed separate branch with ToLCNDV-[IN:Kar:Bel:Rid:14] a Belagavi isolate. The heat map indicated that the virus isolated from the ridge gourd had highest sequence similarity with the ToLCNDV species and Belagavi isolate with respect to both DNA-A and DNA-B components and which proved that the virus is a new strain of ToLCNDV species and variant of Belagavi isolate. The recombination analysis through Splits-Tree version 4 and RDP software indicated that the virus isolated from ridge gourd has derived through genetic exchanges from ToLCNDV-[TH:Mus:07] and ToLCNDV- [IN:Bah:Chi:07]. Results indicated that the virus has evolved as intraspecific recombinant begomovirus. LAMP assay was established for the detection of begomovirus associated with yellow mosaic disease in ridge gourd and has higher sensitivity compared with conventional PCR. Host rang study revealed that, of the 26 plant species tested, none have showed symptoms. While 21 varieties and seven hybrids of ridge gourd tested against disease, showed highly susceptible reaction.
