A NEW METHOD FOR KDENTIFYING COLLETOTRICHUM LAGENARIUM OF WATERMELON INOCULATING WITH DETACHED LEAVES AND JUDGING RESISTANCE WITH AD STANDARD

Colletotrichum lagenarium is a pathogenic factor of some cucurbit crops, such as watermelon (Citrullus lanatus (thunb Manf.), maskmelon (Cucumis melo L.), Cucumber (C. sativus L.) and pumpkin (Cucurbita maxima and C. moschata Dene.), susceptive to anthracnose. It is the most serious disease on leaf and fruit of cucurbit crops under moist condition as well as noe of the worldwide major disease of watermelon.

Being the basic step to develop watermelon cultivar resistant to anthracnose, the study on watermelon cultivars resistance to the disease by artificial inoculation has been widely emphasized by watermelon breeder throughout the world, Goode (1958) and Dutta et al(1960) studied C. lagenarium physiological racial differentiation by inoculation during seedling, adult and fruit developping stages of watermelon respectively, with the results being basically the same. Artificial inoculation with seeding in resistance identification was suggested.

Since our country has started developping watermelon cultivar resistant to anthracnose quite resently, few reports could be found on identification of watermelon cultivars' resistance to anthracnose by seedling artificial inoculation, Liuli adn Wang Ming's (1989) comparative research between detached seeding artificial inoculation and rountine seedling artificial inoculation has shown that the results has no significant difference, the former could accurately reflect watermelon cultivar's inherent resistance to anthracnose.

Suhag and Duhan (1984) studied the best condition for anthracnose preralence by inoculation with C. lagenarium on detached leaf of Calabash, but didn't study how to identify disease resistant cultivar. Cucuzza et al (1986) accurately determined the degree of alfalfa's resistance to Colletotri chum trifolli by spray inoculation on detached leaves. So the method could be used as a substitution for screening disease resistant cultivar in greenhouse.

Comparing with traditional seedling artificial inoculation, detached leaf artificial inoculation has some advantages, such as needing less amount of spore suspension, labour, trial material and cost, especially, getting more reliable results because the environment is more easily to control. In recent years, although many American researchers applies it in identification of watermelon cultivars resistance to anthracnose, no detailed operation procedure has been reported, The purpose of this research was to