Papaya ringspot disease caused by papaya ringspot virus P (PRSV-P), is restricting the commercial cultivation of papaya worldwide. Several measures have been taken to control the disease, including the application of aphicides, identifying host plant resistance, and transgenics. However, only genetically engineered papayas carrying the viral coat protein have been found to effectively control the disease. Transgenic papayas are not cultivated worldwide due to ethical regulations. Assessing the diverse papaya germplasm for resistance to PRSV could be a suitable alternative. Therefore, the present study was undertaken to assess PRSV resistance in 96 accessions, including 36 commercial accessions and 57 wild accessions. To identify novel resistant sources, the accessions were mechanically inoculated with PRSV under controlled conditions. The inoculated plants were continuously monitored for the appearance of PRSV-like symptoms and scored for disease severity, ranging from 0-5. Among all the accessions tested, only two accessions, HCAR 46 (Vasconcellea pubescens) and HCAR 177 (V. stipulate), did not show any symptoms. To further assure that no virus is present in these plants, an RT-qPCR was performed with PRSV coat protein-specific primers. The accession HCAR 46 showed the presence of a faint amplicon of 950 bp. However, no PSRV-specific amplicon was observed in HCAR 177. To further confirm the presence of PRSV, the amplified products were sequenced and showed over 95% sequence similarity with PRSV. The PRSV-resistant genotype identified in the present study could be used to breed PRSV-resistant cultivars.
