水稻白叶枯病抗性基因在不同载体品种上及杂种F_1的抗性研究

本研究测试了八个水稻白叶枯病抗性基因Xa3、Xa4、xa5、Xa7、Xa10、Xa11、Xa14和Xa23在相应载体品种上对华南白叶枯病优势致病菌系Ⅳ型菌和强毒菌系Ⅴ型菌的抗性反应;分析了Xa4、xa5、Xa7和Xa23抗病基因与不同感病品种杂交组合F_1的抗性表达模式以及显性抗病基因Xa7和Xa23在杂交水稻上的利用价值。结果表明:大部分抗性基因在不同载体品种上抗性表达一致,但也有少数基因在不同载体品种上抗性表现不一,甚至截然相反,说明不同遗传背景对抗性表达有影响,而这种影响因不同抗性基因而异。隐性抗病基因xa5(IRBB5)和显性抗病基因Xa23(CBB23)与感病亲本组合的F_1代分别表现感病和抗病,符合隐性基因或显性基因的抗性表达模式;而2个显性抗病基因Xa4(IRBB4))和Xa7(IRBB7)与感病亲本组合的F_1代,有部分组合的F_1代表现抗病,符合显性基因的抗性表达模式,有部分组合的F_1代表现感病,不符合显性基因的抗性表达模式。在杂交水稻上的利用价值方面,Xa7与2个不育系组合的F_1代均表现高感,不宜在杂交水稻上利用;Xa23(CBB23)与4个感病亲本,无论是不育系还是常规稻组合的4个F_1代全部表现抗病,抗性在F_1充分表达,在杂交水稻上有重要的利用价值。

Resistance analysis on major resistant genes of rice bacterial blight in different donors and genetic background

The different donors of eight rice bacterial blight (BB) major resistant (MR) genes, Xa3, Xa4, xa5, Xa7, Xa10, Xa11, Xa14 and Xa23, were inoculated with two Chinese Xoo strains, strain IV and strain V, respectively. The strain IV was a predominant pathotype in south China, while the strain V was severe virulent strain. Two susceptible sterile lines and two susceptible inbred rice were employed to study the effect of genetic background on expression of resistance to BB for Xa4, xa5, Xa7 and Xa23. The value of the application of two dominant resistant genes Xa7 and Xa23 on hybrid rice was also evaluated. The results indicated that the resistance inheritance behaviors of most of the MR genes to the Xoo strains were similar and only a few genes show contradictory reaction in different donors, which suggested that the genetic background would produce an effect on the resistant expression of some R genes. Four resistant donors, IRBB4, IRBB5, IRBB7 and CBB23, were crossed with four susceptible cultivars, WufengA, JitianA, Jingang30 and IR24, respectively, using the resistant donors as male parent. The analysis of F₁ populations revealed that the recessive resistance gene xa5 and dominant resistance gene Xa23 conformed to recessive and dominant expression model, respectively, while the other two dominant resistance genes, Xa4 and Xa7, conferred semi-dominant resistance or showed dosage effect for resis-tance. In conclusion, expression of resistance for xa5 and Xa23 was independent with genetic background, while Xa4 and Xa7 show specific behaviors of resistance related to the receptor background. This study also suggested that Xa7 was not suitable for application in hybrid rice, for the F₁ generation of its cross with two male sterile lines were highly susceptible, and Xa23 (CBB23) had an important value in improving BB resistance of hybrid rice,as the F₁ generations from its cross with 4 susceptible parents, including sterile line and inbred rice, were all show highly resistant.