Abstract: Two different disease resistance muskmelon cultivars (Jiashi and 86-1) were analyzed for the expression profiles of chitinase (CHT) and β-1,3-glucanase (GLU) genes in fruit tissues inoculated with Alternaria alternata. Lesion size was measured and the expression levels of CmCht1, CmCht2 and CmGlu genes were investigated by fluorescent quantitative PCR after subsequent storage at 7 ℃. The results revealed that lesion appeared on the 9th d after infection and expanded until the 24th day. Lesion size in 86-1 muskmelon was 1.12 times greater than in Jiashi muskmelon on the 24th day, illustrating that the latter was more resistant to infection with A. alternate than the former. During the storage period, the relative expression levels of CmCht1, CmCht2, and CmGlu genes were significantly increased, initially rising and then declining. The peak expression levels of CmCht1, CmCht2, and CmGlu genes in the cultivars appeared at intervals of 3, 6 and 3 days, respectively. Moreover, the relative expression levels of CmCht1 and CmCht2 were higher in Jiashi muskmelon than in 86-1 muskmelon during the whole storage period, while the relative expression level of CmGlu was higher in Jiashi muskmelon than in 86-1 muskmelon during 12–24 days of storage. The expression profiles of these three genes were different during the storage period. The relative expression levels of CmCht1 and CmCht2 were high during the early period suggesting that A. alternata induced CHT gene expression, whereas that of CmGlu gene was high during the middle and late period suggesting that A. alternata induced GLU gene expression. Disease resistance in muskmelon was due to the coordination of CHT and GLU expression. Therefore, Jiashi muskmelon revealed stronger disease resistance than 86-1 muskmelon, which was closely related to the expression of CHT and GLU.

Key words: muskmelon, Alternaria alternata, chitinase, β-1,3-glucanase, gene expression