西南水稻白叶枯病菌致病型多样性的垂直分布格局及成因探讨

利用6个含有单抗基因的近等基因系材料为鉴别品种,在水稻的孕穗期采用剪叶接种的方法,测定了西南不同海拔稻区218株水稻白叶枯病菌（Xanthomonas oryzae pv.oryzae）的致病型。结果表明,（1）西南稻区水稻白叶枯病菌致病型具有丰富的多样性,共包含18种,其中9种新致病型为西南地区特有的类型。（2）不同海拔稻区病菌致病型组成存在明显差异,中海拔稻区病菌致病型数量最多,高海拔稻区次之,低海拔稻区最少。低海拔稻区病菌致病型多样性指数、均匀度指数均最低,并且与中海拔和高海拔稻区差异显著。（3）通过分析病菌对抗性基因的克服数量以及鉴别品种病斑长度,表明不同海拔稻区病菌毒力存在明显差异。病菌的毒力与其地理来源的海拔高度呈负相关关系。（4）聚类分析结果显示,以致病型彼此间相似率60%为界,18种致病型可归为4个聚类簇,其中簇Ⅰ毒性最弱,主要集中了高海拔稻区的菌株,簇Ⅳ毒性最强,集中的主要是低海拔菌株。（5）相关性分析表明,病菌致病型多样性特征值与气候类型和寄主品种的多样性呈线性相关关系,气候类型和寄主品种影响病菌致病型的多样性分布,并且寄主品种对病菌的影响程度高于气候类型。就品种的布局而言,低海拔稻区应尽可能使用含有多个抗性基因的聚合品种,而在中、高海拔稻区,应制定好抗性基因轮换的宏观计划,减少低海拔地区向海拔较高的地区稻种的频繁调运,降低水稻白叶枯病的危害。

Analyses on pathotypic diversity ofXanthomonas oryzae pv.oryzae along altitude gradient and driving forces in southwestern China

By using of 6 rice near-isogenic lines containing single resistance gene,the pathotype of 218 strains were tested by clipping method.Our main results are as follows：（1） The tested strains are diversified and include 18 pathotypes,9 of which are only fond in Southwestern China.（2） The population structures of Xanthomonas oryzae pv.oryzae in different elevations are distinct.The highest value of pathotypes was obtained in mid-elevation,the second highest in high-elevation and the lowest in low-elevation.Shannon and evenness index keeps at low level in low-elevation samples and shows significant differences from the strains in mid and high-elevation.（3） A significant difference of strains virulence in different elevations was observed through analyzing the number of resistance genes defeated and the average lesion length of rice lines infected by strains.Moreover,there is a negative correlation between virulence of strains and elevation.（4） A partial correlation was demonstrated when the strains were grouped according to the range of elevations in Southwestern China.18 pathotypes of strains constitute four clusters on the basis of consensus of three clustering statistics.Strains within clustersⅠwith weak virulence are mainly found in the high-elevation,while strains of cluster Ⅳ with strong virulence are mainly found in low-elevation.（5） Factors including species richness,diversity and evenness indices are linearly correlated with the diversity of climate types and rice cultivars.The pathotypic diversity of Xanthomonas oryzae pv.oryzae in different elevations are influenced by climate types and rice cultivars,while the influence of rice cultivars is stronger than that of climate types.Our research lays an important foundation for the layout of the breed in order to reduce disease and thus increase crop production.The rice cultivar containing more resistance genes should be used in low-elevation,while the approach of alternating genes for forestalling the pathogen variation should be applied in mid and high elevations.