Classical Genetic Analysis And QTL Mapping Of Female Fertility In Wheat (Triticum Aestivum L.)

Common wheat (Triticum aestivum L.) is one of the most important food crops in the world. To increase its yield, it is very important to study the issues involved in the crop seed product system and heterosis utilization in wheat. The male sterile line has played an important role in hybrid seed production system. While the female sterile plant may be used as a pollinator in their hybrid seed production to shorten the parents pollinating distance and obtain higher hybrid seed yield. And this can promote to study sex phylogeny and evolution in higher plant. Recently, we found a new mutant XND126, one female sterile line in wheat, and it is vital to study its genetic mechanism in order to further utilize it in the new seed production system. This study results mainly showed the genetic analysis and QTL mapping of the female fertility from the data of the different populations which are derived from common wheat and the female sterile line by microsatellite marker.(1) Three sets of data for the P1, P2, F1, and F2 populations derived from three crosses between the normal fertility wheat cultivars of different ecotypes and the female sterile line (XND126) were used to investigate the inheritance of female fertility in wheat. And that was analyzed by mixed major gene plus polygenes inheritance model in 2005 and 2006. The results from the joint segregation analysis of the four generations showed that female fertility in wheat is controlled by two major genes plus polygenes and the interaction between the two major genes is also detected.(2) An F2 population derived from a cross between an elite variety (Gaocheng 8901) and the female sterile line (XND126) was used to map the quantitative trait loci (QTL) of the wheat female fertility in year 2005. Two marker linkage maps with the phenotype data of the F2 population were used in QTL mapping by the software QTLNetwork 2.0. A major gene locus designated as taf1, which was tightly linked with SSR marker Xbarc95 on chromosome 2DS. The taf1 locus displayed additive and dominant effects and explained 13.64%, 21.54% trait variation respectively by two kind of female fertility data.(3) In 2007, the same cross of the same component population was planted at Haian and Urumqi experimental station separately by tillers split method. In two environments, we detected the taf1 locus was tightly linked with SSR marker Xgdm35. Confident interval was only 2.4 cM which was shorter than the result in 2005, while the contribution of taf1 was more larger, explaining 30.77%, 41.20% trait variation respectively. Geography environment hardly influenced the female fertility. Besides, we also found one epistatic QTL. The same result was found in one environment or two environments of the taf1 locus. We also found extreme recessive class survey provided a fast and cost-effective means for identifying the linked polymorphism marker of female fertility.(4) To fine mapping the taf1 locus, the genetic diversity between XND126 and 59 varieties of common wheat were studied by 14 SSR markers on chromosome 2DS reference map. Among these common wheat, 12 varieties showed higher polymorphism with XND126 than others, which can be selected as hybrid parents to construct new QTL analysis population. High degree of LD was found between QTL taf1 and Xbarc95 in the natural population of female sterile line and 260 varieties. The further marker to taf1 locus, the lower degree of LD, and LD decay was also found. Meanwhile the analysis suggested that the combination of linkage analysis and association analysis may be an efficient tool for QTL fine mapping and understanding the genetic mechanism of female fertility in wheat.