Distribution of Mosaic Disease in Ridge Gourd (Luffa acutangula (L.) Roxb.), Characterization of Associated Virus and Screening for Virus Resistance

Abstract

Aims: A survey was conducted in the ridge gourd growing areas of Kasaragod, Kannur and Kozhikkode district, India, to assess the prevalence of virus diseases. Molecular detection and characterization indicated the presence of mixed infection of Tomato leaf curl New Delhi virus (ToLCNDV) and Cucumber mosaic virus (CMV) in infected samples of ridge gourd collected from surveyed locations. Additionally, a screening of popular varieties/hybrids was undertaken to identify resistance sources against the Begomovirus in Ridge gourd.
 Study Design: CRD design for screening for resistance genotype.
 Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Padannakkad. November 2022 - 2023.
 Methodology: Twenty-five ridge gourd plants were selected from a field and scored during survey. Major weeds and insects in and around the location were collected and identified. Screening for resistance was carried out in vitro by grafting infected scion on to healthy ridge gourd plants. Begomovirus infections were confirmed by polymerase chain reaction (PCR) using specific coat protein primers. Presence of CMV was detected using specific primers.
 Results: Disease incidence (DI) of surveyed locations ranged from 5.3-100 per cent and vulnerability index (VI) from 26.57-84.08. Kunjathur, Thalangady, and Hosabettu areas of Kasaragod district recorded the highest incidence (100%). The highest VI (84.08) was recorded in Thalangady (Kasaragod). Bemisia tabaci and Aphis gossypii were the associated insects and Synedrella sp., Ageratum conizoides and Alternanthera sp. were the associated weeds.
 Screening of varieties indicated moderately susceptible reactions of RG7 and RG10 after 60 days of grafting. PCR based molecular detection of ToLCNDV using coat protein specific primers yielded amplicons of approximately 575 bp. All the isolated sequences were found to be related to ToLCNDV on sequencing and blast analysis. Phylogenetic studies revealed that isolates from Thrikaripur, Mavichery, and Poolacode were closely related to each other. Cucumber mosaic virus, a RNA virus was also detected from isolated samples using specific primers of CMV with an amplicon size of 400 bp.
 Conclusion: The study revealed that the ridge gourd cultivated in areas of Kasaragod, Kannur and Kozhikode were infected with ToLCNDV and CMV; RG7 and RG10 were moderately susceptible among the varieties and hybrids screened. The presence of the begomovirus was detected in weeds indicating its role in perpetuation and spread of the virus disease in the field.