水稻两用核不育系龙S抗稻瘟病主效基因的定位

龙S是一个广谱抗稻瘟病的水稻两用核不育系，利用分子标记技术精细定位其主效抗性基因，对于培育抗稻瘟病水稻新品种具有重要意义。采用来自国内外的41个稻瘟病菌系通过接种鉴定方式对龙S进行了稻瘟病抗谱分析，结果显示龙S的抗性频率为100%，对其中39个菌系表现高水平抗性，与Pi9的携带品种75-1-127抗性频率和抗病级别基本相当。群体遗传分析表明龙S的抗性基因表现为显性遗传方式，对于不同菌系龙S表现出不同的抗病遗传模式，其中龙S对稻瘟菌系318-2的抗性由单基因控制。通过抗病亲本龙S与感病亲本日本晴构建F₂分离群体，采用BSA (bulk segregant analysis)及RCA (recessive class analysis)分析方法，将龙S的主效抗病基因精细定位于第9染色体上的SSR标记M1-M2所在的1.31 cM区间，与已克隆的广谱抗稻瘟病基因Pi5位于相邻的染色体区域。抗谱分析表明，龙S与Pi5、Pii单基因系的抗性频率差异明显，抗谱较后二者更广。龙S主效抗性基因的精细定位，为进一步揭示其与Pi5、Pii的等位关系以及通过分子标记辅助选择培育抗病水稻新品种奠定了基础。

Mapping of the Resistant Gene to Rice Blast in the Dual Purpose Genic Male Sterile Rice, LongS

LongS is a dual purpose genic male sterile rice with broad-spectrum resistance to rice blast. The objective of the present study was to identify the resistance spectrum to rice blast, to analyze the genetic behavior of resistance gene, and to map the major resistance genes in LongS. LongS had a resistance frequency of 100% inoculated with 41 strains of Magnaporthe oryzae. Population genetic analysis showed that the resistance genes in LongS exhibited dominant inheritance, the genetic model of R gene varied depend on the strains of Magnaporthe oryzae. The main-effect resistant gene to rice blast was fine mapped, by using the bulk segregant analysis (BSA) and recessive class analysis (RCA) methods, with the F2 population derived from the resistant parent of LongS and the susceptible parent of Nipponbare. A single resistant gene to the race of 318-2 located on the interval flanked by the SSR markers of M1 and M2 with a genetic distance of 1.3 cM on chromosome 9 were adjacent to the broad-spectrum blast resistance gene, Pi5. Both of the resistance spectrum and resistant frequency of LongS, however, were significantly different to those of resistant gene of Pi5 and Pii. In conclusion, the major-effect resistant gene identified in this study may be a new broad-spectrum blast resistance gene. The DNA markers linked to the new R gene identified in this study should be useful for marker-aided breeding of blast-resistant rice cultivars.