Functional degeneration of the resistance gene nsv against Melon necrotic spot virus at low temperature

摘要

The single recessive gene, nsv, which confers resistance against Melon necrotic spot virus (MNSV), has recently been used to develop virus-resistant melon cultivars in Japan. However, the Chiba isolate of MNSV, a common isolate in Japan, infected resistant cultivars when inoculated melon plants were grown at 15pC. Viral RNAs accumulated in protoplasts from resistant cultivars at both 15 and 20pC. Mechanical inoculation of the cotyledons caused MNSV to spread throughout the leaves at 15pC, but not at 20pC. These results support our novel hypothesis that a temperature-sensitive inactivation of disease resistance genes occurs at the nsv locus in melon cultivars with the resistance gene grown at temperatures below 20pC.