| Wheat(Triticum aestivum L.)is the third largest staple crop in China,which plays a very important role in guaranteeing grain security.In the middle and low Yangtze valley wheat zone,the expansion of direct seeding rice area,extension of rice growth period as well as continuous raining during wheat sowing period,result in the delay sowing of wheat,which causes insufficient growth period,reduces in production and declines in quality.Thousand kernel weight is one of the three components of wheat yield,which is influenced by both grain morphology and grain filling.Therefore,identification different wheat germplasm resources during different sowing dates,mining SNPs of early maturation can contribute to the breeding of late sowing,early maturity and high yield wheat cultivars.A total of 327 wheat germplasm were used in the present study,including domestic and foreign cultivars.In 2018-2019,these populations were grown in Yangzhou and Yancheng in three different sowing dates.Four major kernel traits(grain length,grain width,thousand kernel weight and length-width ratio)were collected after harvest and cleaned.Evaluation and selection of grain character was carried out with analysis of variation,correlation analysis and cluster analysis.Then,the genome-wide association studies of grain traits were carried out with SNP markers during different sowing periods,screening out significant loci correlated with grain traits,loci controlling multiple-traits in the same sowing period and the loci controlling the same trait in different sowing periods.The main research results as follows:1.The kernel traits of wheat germplasms displayed rich genetic variations and diversities among different types of sowing dates and different locations.Grain length ranged from 4.15 mm to 8.15 mm in Yangzhou,and ranged from 4.38 mm to 7.64 mm in Yancheng.Grain width ranged from 2.01 mm to 4.01mm in Yangzhou,2.31 mm to 3.72 mm in Yancheng.Thousand kernel weight ranged from 16.83 g to 63.35 g in Yangzhou,17.42 g to 59.75 g in Yancheng.Length-width ratio ranged from 1.59 to 2.69 in Yangzhou,1.67 to 3.41 in Yancheng.Grain length,grain width and thousand kernel weight all decreased with the delay of sowing date,while length-width ratio increased.The mean variation between sowing dates in Yancheng were larger than that in Yangzhou.Kernel traits didn’t show significant difference between different sowing dates and environments,but it showed significant difference within same sowing date but different varieties.2.The distribution of grain length,grain width thousand kernel traits,length-width ratio and the values from BLUPs in two environments were similarly continuous and relatively normal distribution.Analysis of variation of grain shape and grain size showed that all the kernel trait including grain length,grain width,thousand kernel weight and length-width ratio have significant or highly significant difference between sowing date,variety,environment,variety and sowing date interaction,variety and place interaction.3.Grain length showed positive correlation with grain width,thousand kernel weight,length-width ratio,grain width showed correlation with thousand kernel weight in two kinds of environment and three different sowing dates.While length-width ratio showed negative correlation between grain length and thousand kernel weight.The change of environment and sowing date did not change the correlation between kernel traits,but the size and significance of the correlation between these traits were changed.4.In this study,227,190 and 283 SNP markers associated with kernel traits in three sowing dates were detected,respectively.SNP markers were distributed on 21 chromosomes of wheat.Numbers of marker associated with multiple traits detected in three sowing dates are 25,17 and 40,respectively.Numbers of marker associated with grain length,grain width,thousand kernel weight and length-width ratio detected in all three sowing dates are 19,6,10 and 10,respectively. |
PDF Full Text Request