广东水稻橙叶病病原(MLO)的越冬

研究结果表明,广东水稻橙叶病病原(MLO)的传染介体和越冬介体昆虫只有电光叶蝉(Recilia dorsalis)一种,但其卵不传递该病原到子代若虫,越冬寄主植物只有水稻的再生稻株和落粒自生稻株。在茂名病区的冬、春期间电光叶蝉的带菌虫和带菌再生稻及感病落粒自生稻始终存在,其带菌率分别为2.33％—35.11％、2.37％—17.78％和1.95％—16.67％。在茂名地区由于冬、春气温不甚低,电光叶蝉仍能继续繁殖越冬,并能不断获菌和传病,所以说该病原是动态越冬的。室内试验表明,带菌电光叶蝉的寿命可长达105—125天,而在茂名的秋收期至翌年春播期一般105天,据此推测有些带菌虫可从秋收后直接存活和传病原到春播稻苗。看麦娘(Alopecurus aequalis)用电光叶蝉人工接种并回接水稻成功。但在病区田间调查从未发现病株。以下植物人工接种不成功:野生稻(Oryzea rufipogon)、小麦(Triticum aestivum)、玉米(Zea mays)、李氏禾(Leersia hexandra)、稗草(Echinochloa crus-gallis)。

OVERWINTERING OF THE RICE ORANGE LEAF MLO IN GUANGDONG PROVINCE

Field investigations of the rice orange leaf MLO in 1992 - 1994 revealed that in the epidemic regions of Maoming, Guangdong Province, the ratoon and the volunteer rice plants were two kinds of the most important overwintering hosts, with disease incidence of 2. 37% -17. 78% and 1. 95% -16. 67%, respectively. In the greenhouse, the rice orange leaf MLO was successfully inoculated to Alopercurus aequalis by means of infectious leafhopper, Recilia dorsalis Motsch, and the back-transmisson was also successful, but was not inoculated to Oryzea rufipogon, Triticum aestivum,Zea mays, Leersia hexandra and Echinochloa crus-gallis. However, the rice orange leaf diseased A. aequalis was not found in the field. The zig-zag leafhopper, R. dorsalis, as the only insect vector of the rice orange leaf MLO, was very important for the overwintering of the MLO. Both infectious R. dorsalis adults and nymphs in the field were found over the winter period, and the percentages were 2. 33% -35. 11%. In Maoming region R. dorsalis could multiply in the winter season, and the adults and nymphs could acquire and transmit the MLO easily. The infected rice plants survived in the field all over the winter, although some of them died quickly under lower temperature. It suggested that the overwintering of the rice orange leaf MLO was dynamic. Laboratory tests showed that some infectious adults of R. dorsalis could live for 105 to 125 days. So it is possible that some infectious R. dorsalis can live through the winter and become the primary inoculation resource of the early season rice next year.