桉树青枯病病原菌的分子鉴定及其致病性测定

对华南4个地区的桉树青枯病病原菌进行了分子鉴定和致病性测试研究,以期为有效预防其发生提供依据.分别对来源于不同区域的11株桉树青枯病病原菌进行分子鉴定和致病力强弱测试比较,11株病原菌与Ralstonia solanacearum序列形成支持率为86％分枝,表明其病原菌16S rRNA基因序列与Ralstonia solanacearum具有高度同源性.以桉树无性系DH32-29组培苗为材料,采用伤根法对11个菌株进行致病力测试,不同菌株间在致病性上差异显著(P＜0.01或P＜0.05),以发病高峰期、高峰期发病率和平均发病率进行K-均值聚类分析(K=3),结果表明来源于广东、广西、海南的各菌株间致病性存在差异,HY01、HY02、DA01、HP04菌株与HP05分为1类,DA02和DA03为第2类,而YJ01、HP01、HP02和HP03为第3类.对4个不同地区(采样点)的青枯病菌株平均发病率进行方差分析,结果发现来源广东阳江菌株致病性显著地低于其他来源菌株.不同地理来源菌株之间在致病性上无明显相关性,同一地区内同时存在着致病力强弱菌株,HP03的生物型4-1菌株与其他生物型3菌株在致病性亦无明显的差别.

Molecular Identification and Pathogenicity Bacterial Wilt Isolated from Different Eucalyptus Clones

11 Ralstonia solanacearum isolates obtained from different Eucalyptus clones were used to identify phylogeny and compare differences in pathogenicity.Tissue culture seedlings of the hybrid eucalypt clone DH32-29 were used in pathogenicity tests,which involved infection by dipping of wounded roots.The results of phylogeny showed that the 16S rRNA sequences of all 11 isolates were highly homologous to the type strain of R.solanacearum with 86％ bootstrap support,and all belonged to the same phylotype.There were significant differences in wilt incidence among 11 isolates (P＜0.01 to P＜0.05).Based on three features of the isolates-fastigium,pathogenicity of fastigium and mean morbidity-the isolates were segregated into 3 groups by clustering on k-means:HY01,HY02,DA01,HP04 and HP05 formed one group;DA02 and DA03 formed a second group;and,YJ01,HP01,HP02 and HP03 formed a third group.One-way analysis of variance (ANOVA) was used to compare wilt pathogenicity of the 11 isolates,which had been collected from four different locations;the results showed that an isolate collected from Yangjiang,Guangdong province,differed significantly (P＜0.01) to all others in this respect.In view of all factors,there was no significant difference (P＜0.05) in wilt incidence between 2 of the biovars (biovar 3 and biovar 4-1),which had been obtained from the same plantation.The results from this study provide technical support to both efforts to prevent and control the occurrence of Eucalyptus bacterial wilt and also to the breeding of resistant eucalypt varieties for the eucalypt industry in southern China.