Evaluation of Papaya Plants Tolerant to PRSV Obtained Through Conventional Genetic Improvement

Papaya cultivation is severely affected by the papaya ring spot virus (PRSV), for which one of the alternatives to counteract its damage is to use genetic sources of species and/or varieties tolerant or resistant to the virus. This study aimed to determine the tolerance or resistance of different papaya plant lines obtained through crosses and backcrosses between the Maradol variety and a wild species of Vasconcellea tolerant to PRSV. In this work, an evaluation was conducted on plant lines from a cross between a PRSV-tolerant species (Vasconcellea cauliflora) and the Maradol variety (Carica papaya), both belonging to the Caricaceae family. The study used RT-qPCR to measure the viral load and analyzed disease symptoms at two points (97 and 532 days after planting). Initially, it was observed that all the resulting papaya plants developed symptoms of PSRV; however, as time passed, the results showed that lines resulting from the Criolla, M4, and 54 crosses exhibited moderate tolerance, while papaya lines 89 and 90 proved to have high tolerance. Additionally, it was observed that the M4, 89, and 90 papaya lines exhibited disease recovery, as reflected in a decrease in viral loads and the characteristic symptomatology of the virus. Restoration from a viral infection can be associated with the activation of the plant’s RNA silencing mechanism, which can degrade or prevent the translation of viral RNA in plant cells, thus favoring recovery from the disease. Plants evaluated due to their tolerance and resistance levels could use the mechanisms mentioned above to recover from the damage caused by the PRSV.