Occurrence of papaya ringspot virus (PRSV) infection in India

Papaya ringspot virus isolates infect papaya as well as cucurbit hosts, and occur as two pathotypes, P & W. The cucurbit hosts are known to be infected by both the pathotypes P & W. Field surveys were conducted to document the relative incidence of the PRSV pathotypes (P and W) infecting cucurbit crops in the 6 states of India. A total of 80 cucurbit samples representing Ash gourd, bottle gourd, bitter gourd, cucumber, musk melon, pumpkin, ridge gourd, squash, sponge gourd and water melon hosts were collected and tested by DAC-ELISA based serological assay, which indicated the association of PRSV with 51 samples. The ELISA positive cucurbit samples were subjected to bioassay to ascertain the pathotypes of PRSV, followed by RT-PCR confirmation for the PRSV association. Among all the symptomatic cucurbits samples collected and tested in this study, a higher incidence (100%) of PRSV was recorded on the bottle gourd samples, whereas no or 0% incidence was recorded on ridge gourd samples. Of 51 ELISA positive samples, upon pathotyping on differential host, a relatively higher incidence of pathotype -P (upto 68.63%) was recorded as compare to that of PRSV W, i.e. 31.37% only. Further, the PRSV-P and -W pathotypes also showed a differential relative incidence on different cucurbit hosts, wherein, PRSV-P was found more predominantly (upto 100%) on three cucurbit hosts namely bitter gourd, cucumber and squash, whereas a least incidence (of 30%)was recorded on muskmelon and pumpkin hosts.