Differential expression of genes involved in the response of Carica papaya to Papaya meleira virus Mexican variant
Papaya sticky disease, also known as meleira, causes considerable yield losses in papaya orchards and makes the infected fruits unacceptable for consumption. In Brazil, this disease is caused by two viruses with double-stranded and single-stranded RNA genomes, respectively named Papaya meleira virus (PMeV) and Papaya meleira virus 2 (PMeV2). A virus similar to PMeV-2 named Papaya meleira virus Mexican variant (PMeV-Mx) has also been associated with papaya sticky disease in Mexico. Little information is available about the virus-papaya interaction at the genetic level, in order to sustain the implementation of genetic melioration and effective control of the disease. In this study, 'Maradol' papaya plants were inoculated under controlled conditions with latex from diseased plants. Leaf samples were taken at 5, 10, 15, 20, 25, 30 and 45 days post-inoculation (dpi). The expression of pathogenesis-related (PR) genes and peroxidase genes (POD) was evaluated. It was demonstrated that sticky disease induced the expression of PR and POD genes from 10 dpi, and maximum expression levels were attained at 20 dpi. The results suggest that the defense mechanisms of 'Maradol', although present in the first days after inoculation, decline rapidly and allow systemic infection by the pathogen. These results reinforce the need to continue these studies in other cultivars with less-susceptible responses to papaya sticky disease, in order to discern which genes could confer greater resistance to the plant against this disease and consequently direct the work of breeding.
Magaña-Álvarez, A., Tapia-Tussell, R., Fernandes, P.M.B., Cortés-Velázquez, A. and Pérez‑Brito, D. (2019). Differential expression of genes involved in the response of Carica papaya to Papaya meleira virus Mexican variant. Acta Hortic. 1250, 35-38
pathogenesis-related genes, papaya, peroxidase, viruses, resistance