Association of a betasatellite molecule with sesame curly top virus in severe infection of watermelon

Associated betasatellites with begomoviruses and mastreviruses are small single stranded circular DNA molecules ~1.4 kb in size which have been detected in various infected plants and cause enhanced accumulation of helper viruses as well as induction of severe symptoms (Navas-Castillo & Fiallo-Olivé 2021). In previous study, Sesame curly top virus (SeCTV) (genus Turncurtovirus, family Geminiviridae) was detected in infected watermelon plants showing severe leaf curling in Rudbar-e-Jonub farms (Kerman province, southeastern Iran) (Fig. 1a). Whereas, agroinoculation of watermelon plants with constructed infectious clone of SeCTV resulted in somewhat mild symptoms showing dwarfing and mild yellowing of plants (Fig. 1b) in compared with the natural SeCTV infection of watermelon plants (Hasanvand et al. 2021). In order to investigate the causal agent of severe symptoms in watermelon plant, total DNA were extracted from SeCTV infected sample (isolate 1W) followed by enrichment of circular DNA molecules using (RCA). Initially, possible co-infection of sample with other common geminiviruses in the region including beet curly top Iran virus (BCTIV), chickpea chlorotic dwarf virus (CpCDV) and begomoviruses was tested using PCR assay, specific or degenerate (in case of begomoviruses) primer pairs and RCA product as template.