黄瓜霜霉菌生理分化研究

1982至1985年进行了黄瓜霜霉菌生理分化研究,应用室内离体叶接种和田间病情调查相结合的方法;采集辽宁省七个城市和北方八个城市黄瓜霜霉菌标样,在75个黄瓜品种上进行接种鉴定和自然观察,并在海南岛进行自然诱发观察,结果发现,各地黄瓜霜霉菌的致病性基本一致,不存在生理分化现象。本试验提出利用病斑类型、病斑大小、产孢量、潜育期及叶片气孔密度可试作为黄瓜霜霉病品种抗性接种鉴定的指标。

Studies on Physiological Specialization of Cucumber Downy Mildew

Samples of the fungus collected from the principal cucumber growing regions in North China (including Beijing, Tianjing, Jinan, Zhengzhou, Xian, Harbin, Changchun, Shenyang, Dandong, Dalian, Jinzhou, Tieling and Chaoyang) have been examined for comparative studies on pathogenic reactions during 1982--1985. Seventy-five cucumber cultivars including resistant, moderate- resistant, moderate-susceptible and susceptible types, were tested for the resistance by "culture in vitro" method of artificM inoculation. The results showed that the differential resistance reaction to cucumber downy mildew was conspicuous, and the reaction was in agreement with the natural reaction in field (including North China and Hainan Island). The pathogenic reactions of all samples against one variety in various localities were similar, and the resistant varieties were found to be stable and widespread throughout China. Therefore, the results suggest that physiological specialization of the pathogen does not exist. The results also suggest that the lesion size and colour, sporulation, latent period and numbers of stomata on cucumber leaf may serve as indices for identification of resistance through arficial inoculation. Based on these results, it is believed that the "culture in vitro" method of artifical inoculation, in which detached leaves are inoculated with sporangial suspension and incubated in moist chamber, can be used for selecting and breeding cucumber cultivars with downy mildew resistance. A set of 20 cultivars from 100 varieties may be employed as differentials for resistance identification in China.