Identification Of Synthetic Hexaploid Wheats And Their Usage In Wheat Breeding

Synthetic hexaploid wheat, as the important genetic resources in wheat genetic improvement, provids abundant genetic diversity. In the present study, the agronomic traits, composition of high molecular weight glutenin subunits(HMW-GS) and genomic diversity of 56 synthetic hexaploid wheat introduced from International Maize and Wheat Improvement Center(CYMMIT)were identified, and the agronomic separation characteristics of the offsprings of synthetic wheats and common wheat were also evaluated. The main results are as follows:The average of spikelet number per spike, kernel number and spike number per plant were 17.7, 35.8 and 50.7, respectively. The variation range were 11.6-21.6, 22.2-67.8 and 12.4-113.5, respectively. The spike number per plant in 95% materials was more than 20, of which 25(accounting for 40%) were more than 50. Syn46 had 113.5 spikes per plant, indicating that synthetic hexaploid wheat had greater r tillering, earing and yield potential. The average 1000-grain weight was 36.62 g with the variation range of 19.7-58.8 g. there were10 materials with 1000-grain weight above 50 g. Most of the seed were red and the grain shape were long circle or ovale. 9materials, which accounted for 16.1%, exhibited immunity or near-immunity to wheat powdery mildew in the field, twenty-three, accounted for 41.1%, showed high resistantance, and thirteen, accounted for 23.2%, moderate resistance Synthetic hexaploid wheat provided abundant trait variations and genetic diversity, which could be widely used in wheat breeding programs.Sodium dodecyl sulfate polyacrylamide gel electropheresis(SDS-PAGE) was employed to detect the HMW-GS constitution of the synthetic hexaploid wheat exceptSyn6 and Syn56. 35 allelic variation were detected, showing high polymorphism in the three alleles of Glu-A1, Glu-B1 and Glu-D1. Besides the known good quality submits(such as 17+18, 2*, 5+10), some new ones or combinations were edtected. A new lighter submit, tentatively named Sx, could exist as a single submit or combination with subimits 2, 5, 12,. the synthetic hexaploid wheat showed rich HMW-GS variation, suggesting that they could be used in wheat quality improvement.Molecular markers showed greater genetic diversity in synthetic wheat genomes than those in common wheat cultivars. Moreover, the genetic diversity in D genome was more abundant than that in A genome or in B genome.The agronomic traits of the offspring between the cross of synthetic hexaploid wheat and wheat cultivars were investigated. Wide variations occurred in different hybrid generations for spikelet number, kernel number, panicle number per plant, plant height, spike type, seed color, seed shape and growth period.therefore, new variation types couuld be selected, such as more spikes per plant, more kernels, higher grain weight, better resistance, dwarfing and precocity. Backcross played an important role in improving the agronomic traits of offsprings, and thus should be paid more attention to be applied in wheat breeding.Additionaly, there were 37 and 24 good lines selected from ZM7698/Syn54//ZM7698 BC1F1 and ZM7698/ Syn54 F3, respectively. there agronomic traits were also evaluated.