P-254 - The evaluation of melon resistance to the leaf curl disease

Melon is an economically important crop cultivated worldwide. However, melon leaf curl disease (LCD) caused by whitefly-transmitted begomoviruses constrained production, especially in tropical and subtropical regions. The disease causes symptoms of leaf curling, yellowing, mosaic, and plant stunting, resulting in significant yield losses. Breeding the resistant cultivar is the most promising method for disease control. The tomato leaf curl New Delhi virus (ToLCNDV) and squash leaf curl China virus (SLCCNV) are two major begomoviruses associated with melon LCD in Southeast Asia. Twenty-two melon accessions were screened for ToLCNDV resistance using agrobacteria-meditated virus inoculation. After the disease symptoms of the tested plants were observed for 4 weeks, the presence of the virus was detected by PCR with the virus-specific primers. Two (M1 and M3) out of those tested melon accessions were symptomless and negative for virus detection. The resistance of both melon accessions was purified through self-pollination up to the fourth generation. One purified line each of melon M1 and M3 was also resistant to the SLCCNV infection. The M3 purified melon line was selected for inheritance study and crossed with a susceptible melon line (M9). The ToLCNDV resistance screening of the F1 and F2 generations suggested that the M3 resistance relied on a single recessive gene. Our results reveal the recessive resistance of melon line M3 could be considered as a broad-spectrum resistance to the melon LCD.