Characterization And QTL Mapping Of A High-Tillering And Dwarf Mutant Of Triticum Aestivum L. C.V. Wangshuibai

Wheat is one of the most important crops in the world. Tiller and plant height are two major agronomic traits for genetic improvemnt. Studying the genetic mechanism relating to tiller and plant height will be critical for better utilization of this mutant. A high-tillering and dwarf mutant H167 was obtained from a mutant library of wheat variety Wangshuibai, which was treated with chemical mutagen Ethyl methane sulfonate (EMS). Preliminary study on this mutant had been implemented by Wen(2010). In the present research, phenotypic identification, genetic analysis and QTL mapping of this mutant are implemented in this study. The main results obtained in this research are as follows:Compared with the wildtype, the plant height of the mutant was reduced from 132.47cm to 69.70cm and the number of total tillers was increased from 21.13 to 60.86. Histological observation showed that the dwarf phenotype was due to the decrease in both the number of cells and cell length.Hormone physiology experiments and semi-quantitative RT-PCR of branching-related genes showed that the phenotype of the mutant was related to polar auxin transport, strigalactone pathway and TE-MOC1 pathway. Gibberellin pathway and cytokinin pathway were not be greatly affected by mutant gene in H167.In order to study the inheritance of the tiller and dwarf traits, F2 populations were constructed derived by the reciprocal cross between H167 and Wangshuibai. Significant correlation was found between plant hight and tiller numbers, which showed that these two mutant traits were caused by the same mutant locus, and this mutant locus was a partial recessive gene.Using the RIL population derived from the cross of ’H167xSumai3’, a molecular marker based genetic map was constructed by Joinmap4.0. The genetic map consisted of 283 loci,194 of which were SSR makers,74 of which were EST-STS makers and 15 of whichwere CAPS makers, spanning a total genetic length of 1007.98cM with an average markers interval of 3.56cM. All the 21 wheat chromosomes, except chromosomes 6D, were represented by at least on linkage map.Based on the genetic map and phenotype of RIL population, QTLs related to the number of tillers and plant height were identified using inclusive composite interval mapping method by the QTL IciMapping3.2. When the LOD threshold was set at 2.5, one QTL on chromosome 2D related to plant height was detected and the contribution ratio was 84.02%. Three QTLs related to the number of total tillers were detected on chromosomes 1A,2A and 2D, and their contribution ratios were 6.20%,5.30% and 47.01%, respectively. One QTL on chromosome 2D related to the number of effective tillers was detected and the contribution ratio was 40.39%. The major QTLs related to these three agronomic traits were located in the same region on short arm of chromosome 2D, flanking markers were Xcfdll and Xgpw361. We concluded that this region contained the mutant loci related to phenotype of HI67. This QTL loci may be equal to QHt.crc-2D, which was described by McCartney in 2005.