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杂交水稻南优2号、南优3号近年来在湖南普遍发生枯心凋萎现象。病株除在秧苗后期至分蘖盛期呈现枯心、凋萎死亡和茎基有大量菌脓的突出症状外,拔节期后继续发病的稻株逐渐转为叶片受害,甚至在壮苞期引起死穗现象。此外,在调查中还发现少数常规品种偶有发生,但受害轻微。从枯心凋萎病株上分离的菌株与稻白叶枯菌在培养性状、生理生化性状、血清反应以及噬菌体反应等方面的比较测定中,结果表现一致,可以确定这种枯心凋萎现象是由病原细菌Xanthomonas oryzae(Uyeda et Ishiyama)Dowson引致的凋萎型白叶枯病。“凋萎型”和“普通型”的不同菌株存在侵袭力强弱不同的差异。但侵袭力强的菌株并不局限来自凋萎型病株。湖南分离的4个“凋萎型”菌株和1个“普通型”菌株均属侵袭力强的菌株,而广东提供的1个“凋萎型”菌株和湖南的1个“普通型”菌株则属侵袭力弱的菌株。根据人工接种试验,根部及茎基的伤口是病菌导致稻株枯心凋萎的主要侵入途径,但受菌株侵袭力和品种抗病性强弱的影响。供试的侵袭力强或弱的菌株,通过剪根和针刺茎基接种于感病品种南优2号秧苗上,均可导致系统性感染而出现大量枯心凋萎株;但在抗病品种IR26上,侵袭力强的菌株除引致病株部分叶片呈现症状外,也可引致少量枯心凋萎株,而侵袭力弱的菌株,仅引致部分叶片发病。
Hybrid rice Nanyou 2, Nam You 3 in Hunan in recent years withered withered phenomenon. In addition to the diseased plants in the late tillering stage withered withered, wilt death and stem a large number of pus prominent symptoms, continue to disease after jointing stage of the rice plants gradually turned to leaf damage, and even lead to death in the bracts Spike phenomenon. In addition, in the survey also found that a small number of conventional varieties occur occasionally, but minor damage. The withered-withering phenomenon was confirmed in the comparative determination of the traits isolated from withered wilt strains and rice leaf blight in the aspects of culture traits, physiological and biochemical characteristics, serum reaction and phage reaction Is a withered bacterial leaf blight caused by the pathogenic bacteria Xanthomonas oryzae (Uyeda et Ishiyama) Dowson. Different strains of “wither-type” and “normal type” have different invasiveness and strength differences. However, the invasive strains are not limited to wilt-type strains. Four “wither-type” and one “common” isolates from Hunan were all highly invasive strains, while one “wilt-type” strain from Guangdong and one from “normal” type from Hunan Is a weak invasive strains. According to the artificial inoculation test, the root and stem-based wounds are the main invasion pathways causing the withered and withered wilt of the rice plants, but are affected by the invasiveness of the strains and the resistance of the cultivars. The tested strong or weak invasive strains, by cutting root and needle prick inoculation of the susceptible variety Nanyou 2 seedlings, can cause systemic infection and emergence of a large number of withered wilt strains; but in disease resistance Varieties IR26, invasive strains in addition to lead to some symptoms of diseased plants, but also can cause a small amount of withered twig wilt strains, and weak invasive strains, only led to the onset of some leaves.