Development And Evaluation Of Wheat Yield-Related Qtl Near-Isogenic Lines And Precise Mapping Of A Qtl For Spike Length

The yield of wheat is determined by three main components:spikes per unit area, grain number per spike and grain weight. Understanding the molecular basis of yield component traits could facilitate wheat breeding and improve the wheat production.In the previous study in our laboratory, a lot of yield-related QTLs have been detected using a recombinant inbred line population derived from Nanda2419x Wangshuibai. In the current work, using Mianyang99323, Zhengmai9023, Yangmai17, Wenmai6or Wangshuiai as the recurrent parents, near isogenic lines (NILs) for spike length QTL QSpl.nau-2D, spike number per plant QTL QSn.nau-5A and grain number per spike QTL QGn.nau-4B, and six grain weight QTLs QGw.nau-2D.1, QGw.nau-2D.2, QGw.nau-2D.3, QGw.nau-3A, QGw.nau-4B and QGw.nau-5A, were developed through marker assisted selection. All the NILs have more than95%recipient genome composition exclude one. In addition, a fast efficient technology system for developing yield related QTL-NIL was summared, such as10-12individuals at each generation are suitable for forward selection and the number of markers used in background selection is about150-200, the NILs with high recipient genome composition could be generated after only3rounds of backcrossing.The genetic effect of QGw.nau-2D.1, QGw.nau-2D.2, QGw.nau-4B, QGw.nau-5A, QGn.nau-4B and QSn.nau-5A were validated during the phenotypic evaluation. The field trials revealed that all the QTLs have significant effect on the target trait exclude QSn.nau-5A NIL in Yangmail7background. Compared with their recurrent parents, the four grain weight QTL NILs could significantly increase the hundred grain weight. QGn.nau-4B showed opposite effect on grain number per spike (GN) in different genetic background, NIL of Zhengmai9023background increased GN by5-6grains while NIL of Yangmai17background significantly reduced GN by15grains. The presence of QSn.nau-5A increased spike number per plant (SN) in Zhengmai9023background but showed no significant change in Yangmai17background. Spikes of small grain plants host the kernels and are directly associated with grain yield. Spike characters, including length, spikelet density and fertile floret number, are controlled by polygenes. QSpl.nau-2D is a major QTL controlling spike length identified in wheat (Triticum Aestivum L.) cultivar Nanda2419. In this study,QSpl.nau-2D NIL not only had significantly longer spikes on average than the recurrent parent Mianyang99323but also had significantly higher grain weight, but did not differ in spikelet number and kernel number per spike. In the F2population derived from the NIL, QSpl.nau-2D functioned like a single gene and conditioned the spike length in a partially dominant manner, thus was designated as HL1(for head length). Eighty-nine recombinants in the NIL-derived F2population were identified using flanking markers WMC25and GPW4080and consisted of eleven types of genotype according to the marker loci within the interval. By relating their genotypes with the phenotypes, we found that the introduction of0.9cM interval flanked by Xcfd53and DG371in Nanda2419resulted in longer spikes and higher grain weight in the NIL. The availability of markers closely linked to HL1could facilitate its use in breeding programs.