Indução de resistência ao Papaya meleira virus em mamoeiros

Abstract

Carica papaya L. is one of the most cultivated and consumed fruits in tropical and subtropical regions of the world. Brazil is the world's largest producer of papaya and the states of Espirito Santo and Bahia are responsible for more than 70% of the Brazilian production of this fruit. Diseases of fruit trees are the main limiting factors. Papaya meleira disease, caused by the Papaya meleira virus (PMeV), is one disease that does not have a resistant cultivar. However, the PMeV genome is a doublestranded RNA (dsRNA) and it has been shown that virus resistance in plants can be activated by dsRNA molecules. After detecting the presence of dsRNA, the cell initiates a process of degradation of RNA molecules, which may be viral, thus preventing the progress of the infection. This study aimed to induce resistance to PMeV in papaya seedlings using dsRNA molecules extracted from the viral genome. Four different treatments were evaluated qualitatively and quantitatively by means of molecular diagnosis of the virus in leaf samples by RT-PCR and qRT-PCR (real-time PCR), respectively. The papaya seedlings inoculated only with high load PMeV showed severe infection in the first days post-inoculation, while the seedlings inoculated with high viral load and additional dsRNA showed a milder viral infection, suggesting a reduction in infection by the virus that causes meleira. The combined inoculation of papaya seedlings with PMeV and viral dsRNA reduced the progress of the infection.