青枯雷尔氏菌在植株体内分布及其致病力的异质性研究

 【目的】通过分析青枯雷尔氏菌在不同寄主发病植株、在同一寄主不同侵染状态植株和同一寄主不同发病阶段植株体内分布及其致病力的异质性，从生态位角度来初步探讨该病原菌与植物之间的相互关系。【方法】采用田间采样，室内测定样本的含菌量及其病原菌的致病性（弱化指数），统计分析比较青枯雷尔氏菌在寄主植株体内的分布和致病力的异质性。【结果】番茄和茄子病株体内青枯雷尔氏菌的平均含菌量>100×108 cfu/g，显著高于烟草、花生和生姜（<70×108 cfu/g）。青枯雷尔氏菌的分布在番茄体内依次为根部>中部以上茎>中部以下茎；茄子和花生从根到上部茎依次含菌量逐渐降低；烟草根部和中部茎的含菌量显著高于下部和上部茎；生姜下部茎的含菌量显著高于姜块和中上部茎。不同寄主植物植株体内青枯雷尔氏菌的致病性差异显著，根据弱化指数的划分标准，平均弱化指数的大小依次为茄子>烟草>花生>番茄>生姜；生姜体内的青枯雷尔氏菌的平均弱化指数为0.49（<0.60），明显表现为强致病力，茄子体内的为0.80，接近于无致病力，烟草、花生和番茄为0.64～0.70，属于致病力不确定的菌株。茄子、生姜和花生的健康和发病植株检测的结果表明，仅有花生的健康与发病植株同时存在着青枯雷尔氏菌，而茄子和生姜健株无青枯雷尔氏菌侵染。【结论】青枯雷尔氏菌在不同寄主、不同发病状态、不同生育期植株体内的分布及致病力呈现明显的生态位分化的特征，了解这一特性对于青枯雷尔氏菌控制具有重要意义。

Study on Numerical and Pathogenic Variations of Ralstonia solanacearum Distributed Within the Tissue of Host Plants

The difference of distribution and virulence of Ralstonia solanacearum Smith in the plant was investigated to preliminary discuss the relationship between the pathogen and the plant from the point of view of niche. The results showed that the average contents of R. solanacearum in the infected plants of tomato and eggplant (> 100×108 cfu/g) were significantly higher than in those of tobacco, peanut and ginger (< 70×108 cfu/g). The distribution of R. solanacearum was root> stem above middle part > stem below middle part in tomato, reduced gradually from root to top stem in eggplant and peanut, was significantly higher in root and middle stem than low and top stems in tobacco, and was higher in low stem than tuber and stem above middle. The average of attenuation indexes in the infected plants of different host plants were descending in turn as eggplant > tobacco > peanut > ginger; according to the standard of attenuation index, the pathogen from ginger exhibited as virulent strain with attenuation index of 0.49 (< 0.60), while that from eggplant was close to avirulent strain with attenuation index of 0.80 and those form tobacco, peanut and tomato belonged to strain of uncertain virulence with attenuation index of 0.64-0.70. When both healthy and infected plants of eggplant, ginger and peanut were tested, only peanut had R. solanacearum in the two kinds of plants with different infection status. At three disease stages, all the amounts of R. solanacearum in low stem of eggplant were higher than in middle and top stems; the content at different parts all reduced while the course of disease developed from initial stage to middle stage, but no significant difference was found between middle and later stages. The pathogeny didn’t display obviously virulent in the plants of eggplant at different disease stage, but the attenuation index reduced as the disease developed which suggested that the virulence increased.