QTL Mapping For Yield Traits And The Effects Of 1BL/1RS Translocation On Yield In Common Wheat

Yield improvement is one of the major objectives in wheat breeding programs. Identification ofgenes related to yield traits is very necessary for improving wheat yield potential. Although the1BL/1RS transloction has positive effects on many agronomic traits, it reduces wheat quality.Therefore,it is important to studythe genetic bases ofyield traits and estimate the genetic effects ofthe 1BL/1RS translocation on yield traits for developing wheat cultivars with high yield and goodquality. The objective of this study was to identify quantitative trait loci (QTL) for yield traits andkernel characteristics and to analyze the genetic effects of the 1BL/1RStranslocation on yield traits,kernel characteristics and powdery mildew reaction in common wheat. A total of 240 F5:6recombinant inbred lines (RILs) derived from a cross between PH82-2-2, with early maturity, highquality, and resistance to several diseases, and Neixiang 188 (1BL/1RS), a widely grown variety,was planted in Tai'an, Anyang, and Jiaozuo in the 2004-05 cropping season. Yield traits and kernelcharacteristics were investigated for QTL analysis with SSR markers. The main results aresummarizedbelow.1. Two parents, PH82-2-2 and Neixiang 188, were screened for polymorphism with 1960 SSRmarkers. Ofthose, 296 werepolymorphic between the parents.The frequencyofpolymorphismwas15.10%.In all, 169 markers werefinally mappedon 21 linkage groups with softwaresMapManagerQTXb20 and MapMaker/Exp 3.0. The169 SSR loci covered the whole wheatgenome (1945.71cM)with anaveragegeneticdistanceof11.51cM.2. The QTLanalysis was performed with the software QTLCartographer2.5 based on compositeinterval mapping (CIM). A total of 42 putative QTLs for grain yield, one-thousand-grain weight,spikenumber,grainnumberperspike,plantheight,headingdateandpowderymildewseverityweredetected in Anyang, Jiaozuo, and Tai'an with LOD thresholds of 2.5. These were located onchromosomes 1A, 1B, 2A, 2B, 3B, 3D, 4A, 5B, 5D, 6B, 7A and 7B. Of those, 37 QTLs wereconsistent with those in previous reports. A QTL on chromosome 5B (Xgwm408-Xbarc142) foryield was significant in Anyang and Jiaozuo, explaining 13.55% and 10.25% of the phenotypicvariance, respectively. A major QTL on chromosome 1A in the interval Xbarc269-Xwmc120 wasdetected for spike number in three environments, explaining 11.26-14.78% of the phenotypicvariation. Some minor QTLs affectingthousand-grain weight, grain number per spike, plant height,...