Abstract: The resistance of cultivar and wild species had been identified used the method of leaves inoculate with Podosphaera xanthii. The results showed that the wild germplasms were resistance to Podosphaera xanthii Race1. There were 85 bp differences between wild and cultivated species after cloning and sequence analysis of their MLO gene. Then CmMLO2 was expressed in wild germplasm using fluorescence-labeled Agrobacterium-mediated method. A positive transgenic plant was successful invasion by Podosphaera xanthii Race1. These results suggested that wild species maybe failing encoded MLO protein，resulting the function of MLO negative regulation to Podosphaera xanthii was losing，which caused wild species had a broad-spectrum resistance to Podosphaera xanthii.

Key words: melon, CmMLO2, mutation, Podosphaera xanthii