Emerging squash leaf curl Philippines virus on pumpkin in India: their lineage and recombination

A roving field survey conducted during the year 2023, assessed the viral disease incidence of about 97% on pumpkin in a farmer holding at Coimbatore (Tamil Nadu, India). The diseased plants expressed symptoms such as severe mosaic, leaf malformation, upward cupping of terminal leaf, yellowing, and stunting. The disease was successfully transmitted by the whiteflies (Bemisia tabaci) to healthy pumpkin, with 24 h of acquisition access period and 12 h of inoculation access period. The samples were found to be associated with bipartite begomoviral DNA-A component of squash leaf curl Philippines virus (SLCPHV) along with DNA-B component of squash leaf curl China virus (SLCCNV) based on rolling circle amplification and DNA sequencing. The nucleotide sequence of DNA-A of SLCPHV (OR860425) shared the highest nucleotide identity of 94.5% with the previously reported SLCPHV isolate of Philippines. The DNA-B component of SLCCNV (OR860426) showed 94.9% identity with the Indian pumpkin isolate. The phylogenetic analysis explicated that the SLCPHV and SLCCNV isolates from pumpkin had common ancestry with SLCPHV and SLCCNV isolates from Philippines and India, respectively. Further analysis predicted intraspecies recombination events on their genome. This study confirms the association of non-cognate SLCPHV (DNA-A) with SLCCNV (DNA-B) causing mosaic disease on pumpkin and to the best of our knowledge it constitutes the first report of SLCPHV occurrence in India.