无毒基因avrXa3介导的水稻白叶枯病菌在不同水稻品种上的致病适应性分析

Pathogenic Fitness of avrXa3 Mediated Xanthomonas oryzae pv. oryzae Strains on Rice Varieties

水稻白叶枯病菌[Xanthomonas oryzaepv.oryzae(Ishiyama)Dye]是水稻上重要的细菌病害之一,探明无毒基因avrXa3和含不同抗病基因水稻品种间的互作对于制定有效的病害防治措施有着重要的意义。根据无毒基因avrXa3的序列,构建了水稻白叶枯PXO99A菌株缺失5个串联的无毒基因的突变体PXO99△avr。将avrXa3导入PXO99A和PXO99△avr后,得到衍生菌株PXO99A/avrXa3,PXO99△avr/avrXa3,与36个含不同抗病基因的水稻品种进行互作分析。结果显示,导入avrXa3后的菌株在不同的水稻品种上表现出明显的寄生适应性变化。进一步分析证明无毒基因avrXa3在Wase Aikoku 3、IRBB2、IRBB3、IRBB203、IRBB204、IRBB205、IRBB211、IRBB53、IR24、TN-1等11个水稻品种上病斑缩短,表现明显的无毒活性;在IRBB21、IRBB10、IRBB14、IR26、Cas209、Java14这6个品种上病斑明显变长,体现无毒基因的毒性功能。表明无毒基因avrXa3对PXO99A中其他无毒基因的表达有明显的干扰作用,单个效应分子的变化也会使细菌在不同水稻品种上的寄生适应性发生复杂的改变。

Bacterial leaf blight,a lethal disease of rice caused by Xanthomonas oryzae pv.oryzae（Ishiyama）,is one of the most destructive diseases of rice in Asia.Understanding the interaction between the bacterial avrXa3 gene and its host rice resistance gene is imperative for the development of effective disease controls.PXO99△avr,an avrXa3 gene deletion mutant,derived from PXO99A by homologous recombination was obtained.The avrXa3 was introduced into PXO99A and PXO99△avr to produce the derivatives,PXO99A/avrXa3 and PXO99△avr/avrXa3,and the interaction between the two derivatives and 36 rice varieties with different resistance genes was analyzed.The inoculation assays of 36 rice varieties showed that the pathogenic fitness of PXO99A/avrXa3 and PXO99△avr/avrXa3 on rice varieties had obviously changed,compared with PXO99A and PXO99△avr,respectively.The avrXa3 on eleven adult rice plants of Wase Aikoku 3,IRBB2,IRBB3,IRBB203,IRBB204,IRBB205,IRBB211,IRBB53,IRBB55,IR24 and TN-1,showed avirulence which was characterized with shortened lesion length,and the avrXa3 on six rice varieties of IRBB21,IRBB10,IRBB14,IR26,Cas209 and Java14,showed virulence which was featured by longer lesion length.Therefore,the avrXa3 showed significant interference with expression of other innoxious genes in PXO99A.The changes in individual effector molecules may cause the subtle alterations in bacterial pathogenicity of relevant rice varieties.