MOLECULAR EVALUATION OF POTENTIAL RESISTANCE TO PAPAYA RING SPOT VIRUS IN MOUNTAIN PAPAYA (VASCONCELLEA CUNDINAMARCENSIS)

Abstract

Papaya Ring Spot virus (PRSV) is a devastating viral disease in papaya cultivation in Sri Lanka. It was reported that mountain papaya (Vasconcellea cundinamarcensis) exhibits resistance to PRSV. Therefore, this study was conducted to evaluate the potential resistance to PRSV in mountain papaya to be used in papaya improvement breeding programs. Carica papaya and V. Cundinamarcensis were inoculated with PRSV by mechanical inoculation technique and symptoms were evaluated visually. In order to detect the latent infection, a molecular method was developed. PRSV RNA genome segments were amplified using three sets of primers by RTPCR and an amplicon was sequenced to confirm the identity of PRSV. Functional ability of the cDNA was examined using SAND family protein gene (sand) as the reference gene. According to the results, visual symptoms were not observed in mountain papaya while standard visual symptoms appeared in Carica papaya. Three sets of primers were able to amplify the corresponding amplicons in inoculated Carica papaya and sequencing data confirmed that the amplicon was from PRSV. Negative amplification was observed in mountain papaya from the three sets of primers although sand gene amplification was observed, proving the correct functionality of cDNA. Therefore, it can be concluded that mountain papaya is likely to be resistant to PRSV.