Genetic Dissection Of The Grain Set On Basal And Apical Spikelets And Other Yield-related Traits In Released Cultivars Of Bread Wheat

Bread wheat is one of the most important crops in China,and increasing the yield isalways the major goal in wheat breeding.Development of higher yield potential cultivars isthe key question need to be solved by breeders though analyzing the yield components andtheir genetic balance.At present,among yield-related traits,increasing kernel number perspike might be one important way to further increase the wheat yield.Low grain set ofbasal and apical spikelets is one of most important factors affecting kernel number perspike in many wheat cultivars.So it's necessary to analyze the genetic characteristics ofthese traits.In this study,two natural populations including diverse bread wheat cultivars?lines?were genotyped by 106 SSR markers in order to identify favorable loci or alleles of grainset on basal and apical spikelets,and other yield-related traits though association analysis.Some favorable alleles were verified in a segregating DH population.The purposes of thisstudy were to provide information that may be useful for future molecular breeding in theYangtze Valley.The major results were as follows:A set of 220 cultivars was used to study the grain set on basal and apical spikelets indifferent sowing dates?early sowing,middle sowing,late sowing?and environments?Yangzhou and Jingzhou?.Correlation analysis indicated that the grain set on basal andapical spikelets was closely correlated with kernel number per spike.The analysis of linerregression suggested that the kernel number per spike was positively related with the grainset on basal and apical spikelets,while negative related with the thousand-kernel weight inseries of cultivars named Yangmai and Ningmai.Association mapping revealed 60significant associations between 39 SSRs and seven grain set related traits,and theseassociated loci distributed on seventeen wheat chromosomes except 3A,3D,4A and 7D.Total 55 favorable alleles associated with the grain set in basal and apical spikelets weredetected,the average alleles carried by series of cultivars named Ningmai and Yangmaiwere 21.54 and 17.14,respectively.Yangmai18,Ningmai 9 and Ning 0569 carried 33,36and 37 favorable alleles,respectively,which might be the reason for Ningmai with highergrain set ability in basal and apical spikelets because of the additive effects of these alleles.Using another population including 230 cultivars,seven other yield-related traits wereanalyzed over mutil-years and mutil-environments.These seven traits included kernelnumber per spike?KNPS?,kernel weight per spike?KWPS?,plant height?PH?,spike length?SL?,spikelet number per spike?SNPS?,sterile spike number?SSN?and thousand-kernelweight?TKW?.Association mapping detected 73 significant associations between 50 SSRsand the seven traits,and the phenotypic explanation rate?R²?of associations ranged from1.54%to 23.93%.These associated loci distributed on eighteen chromosomes except 4A,7A and 7D.The yield-related favorable alleles,including X_gwm35-1A₁₃₈,X_gwm337-1D₁₈₆,X_gwm102-2D₁₄₄,and X_gwm132-6B₁₂₈ were validated in a double haploid?DH?populationderived from Hanxuan 10 × Lumai 14.