Study Of Usda-ars Nsgc Wheat Germplasm For Drought Tolerance,high-yield And Qtl Analysis For Yield Associated Traits

Wheat?Triticum aestivum L.?is the one of major agriculture crops in the world,mainly is planted in arid and semi-arid regions and is critical to food security of our country and the world.Wheat accessions from the USDA-ARS National Small Grains Collection?NSGC?were from global,further explore the wheat germplasm resources with drought resistance,high yield and dwarf is important for broadening the combination of good parents and the diversity of genetic basis,and increasing crop drought resistance and production.This study assessed the agronomic performance and drought tolerance in 198 winter wheat accessions under irrigated and terminal drought environments in two seasons.Three field experiments were carried out examining 10high-yielding wheat accessions of diverse origins and 10 locally adapted cultivars with high-yielding under irrigated,terminal drought,and dryland conditions in the southern Idaho,which was to evaluate the interaction between post-anthesis physiological traits,especially leaf-level photosynthetic capacity,senescence,and yield components on grain yield in different moisture regimes.To explore the potential utilization of Rht4 in wheat improvement,we investigated and compared the effects of Rht4 and Rht-B1b on the plant height and yield components using four groups of recombinant inbred lines derived from the cross between“IDO444”?tall,no known dwarfing alleles?and“Rio Blanco”?semi-dwarf,Rht4+Rht-B1b?grown under two water regimes.Genome-wide linkage mapping was used to identify QTLs associated with these traits using high-density genetic linkage map in a spring wheat double haploid?DH?population derived from a cross between‘SY Capstone'and‘UI Platinum'.The DH population was genotyped using the wheat 90K iSelect platform,SSR and STS markers.The main results are as follows.1.Screening of wheat germplasm from USDA-ARS NSGCThis study assessed the agronomic performance,drought tolerance and productivity in 198winter wheat accessions under irrigated and terminal drought environments in the 2012–2013season,and repeated the test under terminal drought only during the 2013–2014 season.Day to heading,plant height,thousand kernels weight and grain volume weight and grain yield had the high H².In all three environments,the early accessions had the best agronomic performance.The early and intermediate accessions produced higher grain yield,heavier thousand kernels weight and grain volume weight,and headed earlier,were shorter than than the late maturity accessions.In the irrigated environment,the intermediate accessions had similar grain yield and thousand kernels weight as the early accessions,while lower thousand kernels weight and grain volume weight in the terminal drought environments.The positive correlation between grain yield and days to heading suggests that the‘late early'types in the early maturity were the most successful.Plant height,thousand kernels weight,grain volume weight and grain yield exhibited marked reductions under the terminal drought conditions.To quantify the response of accessions to drought,the drought susceptibility index?DSI?was calculated for each accession using 2012–2013 data grain yield differences between the terminal drought and the irrigated plots.Among these accessions,109 had smaller DSI values?DSI<1?in the 2012–2013 seasons.The cluster analysis of DSI in the 2012–2013 season generated four clusters,cluster 1?0.00–0.52?,including 57 accessions.The membership function value of drought tolerance?MFVD?of each accession was estimated according to the primary trait grain yield and two correlated traits,plant height and grain volume weight.Eleven accessions were highly drought tolerant(A,₄)?0.84)and 21 accessions were drought tolerant(B,0.75?₄)<0.83).Out of 198accessions evaluated,twenty-three had high yield stability and drought tolerance according to the drought susceptibility index and membership function value of drought tolerance.The eight of twenty-three accessions identified?four early and four intermediate?had high grain yield in three environments.The utilization of the selected wheat germplasm resources with drought resistance,high yield and dwarf in wheat breeding will useful for the drought resistance and grain yield improvement.2.Relationship between canopy photosynthetic traits and yield-related traits of high-yielding wheat germplasmThree field experiments?experiment 1,2 and 3?were carried out examining 10 high-yielding winter wheat accessions of diverse origins and 10 locally adapted cultivars with high-yielding.Genotype differences were found in leaf-level photosynthesis and senescence,canopy temperature depression,grain yield,and yield components in each water regime.In the drought conditions?Experiment 2 and 3?,the range of photosynthetic rate declined slightly from anthesis to late grain filling,compared with the irrigated condition?Experiment 1?.In all three moisture regimes,positive correlations were observed between photosynthesis and grain yield and traits related to grain numbers?numbers of spikelets,the number of spikes per m² and number of grains per m²?that were dependent on the timing or physiological growth stage of the photosynthetic measurement:highly significant correlations were found in the mid-and late grain filling stages,but no correlations at anthesis.In each water regime,flag leaf senescence was negatively correlated with photosynthetic rate,grain yield,numbers of spikelets,grains per spike,plant height and days to heading,while canopy temperature depression at the late grain filling stage was positively correlated with photosynthetic rate at the late grain filling stage.Grain yield was closely associated with traits related to grain numbers.In the irrigated conditions?Experiment 1?,canopy temperature depression at the middle grain filling stage was not correlated with photosynthetic rate at anthesis,the mid-and late grain filling stage and flag leaf senescence,but was positively correlated with grain yield,numbers of spikelets,grains per spike and plant height.While in the terminal drought?Experiment 2?,canopy temperature depression at the middle grain filling stage was positively correlated with photosynthetic rate at the mid grain filling stage,grain yield,grains per spike,grain weight and days to heading,but was negatively correlated with flag leaf senescence.These findings provided evidence that at which time sustained photosynthesis and delayed senescence were critical in filling grain.The results also suggest that late season photosynthesis and delayed leaf senescence is driven by the size of the reproductive carbon sink,which was largely governed by factors affecting grain numbers.3.The interactive effects of Rht4 and Rht-B1b on agronomic traitsTo explore the potential utilization of Rht4 in wheat improvement,we investigated and compared the effects of Rht4 and Rht-B1b on the plant height and yield components using four groups of recombinant inbred lines derived from the cross between“IDO444”?tall,no known dwarfing alleles?and“Rio Blanco”?semi-dwarf,Rht4+Rht-B1b?grown under two water regimes.Rht4,Rht-B1b and Rht4+Rht-B1b significantly reduced plant height by 11.5%,19.3%and 18.2%,respectively.There were no additive effects on plant height in Rht4+Rht-B1b lines.Both Rht4 and Rht-B1b significantly reduced internode length and lodging score with stronger effects by Rht-B1b.Water stress affected the plant height related traits of the single Rht-B1b lines more than that of the Rht4 lines,except for distance from spike to flag leaf ligule.Rht4had little or no adverse effect on the coleoptile length and seedling root characteristics,but Rht-B1b and Rht4+Rht-B1b had significantly reduced the coleoptile length and had positive effect on the seedling root characteristics.Grain number was increased by Rht4 and Rht-B1b,but higher spike numbers was only observed in lines with Rht-B1b.Both Rht4 and Rht-B1b significantly reduced thousand kernels weight.Rht-B1b reduced above-ground biomass but increased grain yield and harvest index,while Rht4 had less effect on these traits,compared with tall lines under both well-watered and water-stressed conditions.The Rht4+Rht-B1b lines produced the highest yield under both water regimes,with more grain number,greater spike number and higher harvest index.Rht4,Rht-B1b and Rht4+Rht-B1b had no effect on grain volume weight,while Rht4 had no effect on the grain protein content,but Rht-B1b had negative effect on the grain protein content.In conclusion,Rht4 did not show advantages over Rht-B1b on grain yield,but Rht4+Rht-B1b did,in both water regimes,which suggests that Rht4 should be combined with Rht-B1b in wheat improvement.4.Linkage map construction and QTL for yield associated traitsGenome-wide linkage mapping was used to identify QTLs associated with these traits using high-density genetic linkage map in a spring wheat double haploid?DH?population derived from a cross between‘SY Capstone'and‘UI Platinum'.The linkage map was constructed using a total of 9687 SNPs,44 SSRs,and 3 STSs for vernalization genes?Vrn-A1,Vrn-B1 and Vrn-D1?,with whole linkage map of 3633.19 cM and marker density of 0.37 cM between adjacent markers.A total of 210 QTLs were detected for the 14 traits on 43 linkage groups,representing the whole 21 wheat chromosomes.Among these QTLs,23 were for days to heading,15 were for plant height,83 were for yield components,18 were for grain yield and71 were for yield-related physiological traits.The QTLs identified with pleiotropic effects were:the QTL on chromosome 5A involved in HD,spikelet number spike^-1,grain number,spike length and chlorophyll content index at the GF-1 stage?CCIg1?and chlorophyll content index at the GF-2 stage,the QTL on chromosomal region 6A-2 regulated PH and spike number,and the QTL on 2D-1 affected both thousand kernels weight and canopy temperature at the GF-2stage.Of the 10 stable QTLs consistently detected across four or five environments,1 QTLs for plant height,4 for yield-related traits and 4 for canopy temperature and chlorophyll content index were identified as novel loci compared with previous studies.Four QTL-rich chromosome regions on these traits were found on chromosomes 4A-1,1B-1,5B-2 and 2D-1.These QTLs and linked molecular markers would be very useful in assisted selection for improving grain yield in spring wheat breeding.In conclusion,the results revealed that through screening the wheat germplasm from USDA-ARS NSGC,23 wheat accessions with drought resistance,high-yielding and dwarf were identified.It was analyzed and identified that Rht4 should be combined with Rht-B1b in wheat improvement under the irrigated and terminal drough conditions.90 K SNPs were used for genetic map construction and a total of 210 QTL for yield associated with traits were detected,which is important for exploring excellent allelic variation,using wheat germplasm with drought resistance,high-yielding and dwarf in breeding and improving grain yield.