小麦突变体D51抗秆锈性遗传分析及其抗性基因SSR标记

D51是优良品系龙6239经辐射诱变和组织培养相结合获得的高产优质抗秆锈突变体材料，对我国优势秆锈病21C3CPH、21C3CKH和21C3CTR小种均表现免疫。利用来自D51/龙6239、D51/中国春的2个F₂群体和来自D51/龙6239的1个F₂群体分别在苗期和成株期进行21C3CPH小种接种，抗病反应型鉴定表明，3个F₂群体中抗感分离比例均为3∶1，说明D51抗秆锈性受一对显性基因控制，全生育期表达，部分D51/龙6239 F₂植株的F₃株系的抗病鉴定进一步验证F₂鉴定的可靠性。利用675对小麦SSR引物和185株D51/龙6239 F₂分离群体对SrD51基因进行标记定位，将SrD51定位在5D染色体的短臂上。其中SSR标记Xgwm190和Xwmc150与SrD51基因的遗传距离分别为18.58和21.33 cM，并分别位于目的基因的两侧。由于已知的秆锈抗性基因仅有Sr30被定位在小麦5DL上，且Sr30不抗34C2MKK和34C2MFK，而突变体D51的原亲本龙6239不抗21C3CPH、21C3CKH和21C3CTR，却对34C2MKK和34C2MFK表现免疫抗性。因而推断此突变体的秆锈抗性基因可能是一个新基因，暂命名为SrD51。

Genetic Analysis and SSR Mapping of Stem Rust Resistance Gene from Wheat Mutant D51

Stem rust caused by Puccinia graminis f. sp. tritici is one of the main diseases of wheat (Triticum aestivum L.) worldwide. Wheat mutant line D51, form a highly susceptive cultivar ‘L6239’ to the three races notated and cultured with immature embryo, shows resistance to prevailing races 21C3CPH, 21C3CKH, and 21C3CTR of P. graminis f. sp. tritici in China. In this paper, number of the resistance genes in mutant D51 and the expression stages were studied with inoculation identification and microsatellite (SSR) marker analysis. Two F1 populations from the crosses of D51×L6239 (60 individuals) and D51×Chinese Spring (60 individuals), their F₂ populations (185 and 175 individuals respectively) at seedling and one F₂ populations derived from the cross of D51×L6239 (194 individuals) at adult stage were inoculated with pathogen race 21C3CPH to test their resistance. All F₁ individuals of the two crosses were immune to stem rust at both seedling and adult stages. The response pattern of the three F₂ populations showed that the R:S segregation ratio fit 3:1, suggesting the stem rust resistance of D51 controlled by a single dominant gene, and expressed in whole growth period. The identification to stem rust resistance by F3 progeny test confirmed the credibility of F2 population test. Segregating populations and small population analyses were used to identify chromosomal region and molecular markers linked to the gene by SSR markers method. A total of 675 SSR markers and 185 individuals of D51×L6239 F₂ population were used to search genetically linked makers to the target gene. Using Mapmaker3.0 and Map-draw with Kosambi’s function and other options left at default values, molecular mapping revealed that the gene was located on the chromosome 5DS, and linked with and blanked by two SSR markers Xgwm190 and Xwmc150 at 18.58 and 21.33cM, respectively. According to references reported, the only one stem rust resistant gene Sr30 is located on the wheat chromosome 5DL, and has no resistance to 34C2MKK and 34C2MFK, and parent L6239 of mutant D51 is without resistance to 21C3CPH, 21C3CTK and 21C3CTR, but with resistance to 34C2MKK and 34C2MFK.The results above indicate that the gene identified in this paper might be a novel resistance gene to stem rust, designated SrD51 tentatively.