河北省西瓜枯萎病菌生理小种分化及其分布

采用国际公认的鉴别寄主Sugar Baby、Charleston Gray和Calhoun Gray的病株率作为抗性分级标准，对采集于河北省西瓜种植区46个县（市）的西瓜枯萎病菌系进行了致病性测定。根据鉴别寄主对供试菌系的抗感反应，将46个西瓜枯萎病菌系划分为0号、1号和2号3个不同的生理小种，分别包括8，30和8个菌系，占供试菌系的17.4%、65.2%和17.4%；0号生理小种菌系致病性最弱，仅使品种Sugar Baby感病，以冀中和冀南居多；1号生理小种菌系致病力中等，使鉴别寄主Sugar Baby和Charleston Gray感病，而使Calhoun Gray抗病，分布在整个河北省西瓜种植区；2号生理小种的菌系致病力最强，使3个鉴别寄主均能感病，主要分布在冀中和冀北。

Distribution and Differentiation of Physiological Races of Fusarium oxysporum f.sp. niveum in Hebei Watermelon-growing Areas

Based on the resistant and susceptible reaction in watermelon varieties, Sugar Baby、Charleston Gray and Calhoun Gray, which is susceptible, moderate and resistant, respectively. 46 isolates from watermelon-growing areas were classified into 3 races like race 0, race 1 and race 2 which were 8 (17.4), 30 (65.2), and 8 (17.4%), respectively. Pathogenecity of race 0 isolates are weakest which only make Sugar Baby susceptible; isolates of race 1 are intermediately pathogenetic, they make Sugar Baby and Charleston susceptible Gray but Calhoun Gray resistant; isolates belonging to race 2 possess the strongest pathogenecity, which make 3 hosts susceptible. Isolates of race 0 mainly distribute over the central and southern Hebei province, whereas race 2 cover the middle and north of Hebei, isolates of race 1 exist in the whole watermelon-growing areas in Hebei province.