Genome-wide Association Study For Nutritional Quality And Agronomic Traits In Common Wheat Lines Derived From Wild Emmer Wheat

Wheat is one of the main sources of human nutrients which account for about 30% of all cereal production in the world.The quality and yield of wheat play an important role in human health and survival.However,malnutrition caused by low concentrations or deficiencies in human staple food affects a large proportion of the world population.At the same time,the narrow genetic basis of modern wheat varieties has become a major obstacle to breeding new varieties of "high quality-high yield" wheat.Therefore,the exploitation and utilization of germplasm resources is the key to achieving "high quality-high yield" breeding.Wild emmer wheat(Triticum dicoccoides,AABB,2n=4x=28)is the tetraploid progenitor of cultivated wheat which has high protein,high Fe/Zn content,stress tolerance,resistance to disease and other excellent characteristics.It is an extremely valuable germplasm resource for the improvement of common wheat.Therefore,transferring excellent characteristics from wild emmer wheat into common wheat is an important basis for breeding high quality-yield varieties.With the rapid development of genomics and bioinformatics,genome-wide association study based on linkage disequilibrium provides a new way to explore key genetic loci for controlling nutritional quality traits and major agronomic traits.In this study,the phenotypes of four nutritional qualities and six agronomic traits of the populations composed of 163 wild emmer wheat D1 and its introgression lines and 86 wild emmer wheat D97 and its introgression lines were identified in four environments.Secondly,24022 DArT markers covering the whole genome were used to analyze the nutritional quality and main agronomic traits of introgression lines derived from wild emmer D1 and D97,and to explore marker-trait association(MTA)and candidate genes for high grain protein content and high micronutrient concentration and agronomic traits.Furthermore,the genetic improvement potential of wild emmer wheat for nutritional quality and yield was discussed in common wheat background.It provides a good theoretical and material basis for the effective application of wild emmer wheat in the breeding of "high quality-yield" wheat.Main results for this study are as follows:1.Phenotypic analysis of grain protein content(GPC)in introgression lines derived from wild emmer: The GPC variation of the introgression lines was 11.97-19.73%,with an average range of 14.39-14.73%,which was greater than 14% in all test environments,reaching the indicator of strong gluten wheat protein,significantly higher than that weak gluten parent CN16(12.00-12.90%).Correlation analysis showed that no significant negative correlation between GPC and TKW.These results indicated that the high GPC characteristics of wild emmer wheat were further transmitted to the introgression lines through distant hybridization,and under the background of common wheat,the improvement effect on GPC is significant without negative impact on TKW.Even the TKW of some materials exceed the parent CN16(46.80 g),achieving the improvement effect of both GPC and TKW.2.Phenotypic analysis of grain micronutrients concentrations(GFeC,GZnC,GMnC)in introgression lines derived from wild emmer: The mean range of GFeC(80.90-109.68mg/kg)and GZnC(55.99-68.75 mg/kg)were significantly higher than the parent CN16(38.15-49.20 mg/kg,36.67-41.64 mg/kg)in all environments,while the mean range of GMnC(30.36-39.42 mg/kg)was higher than that CN16(23.43-27.03 mg/kg),but the difference was not significant.These results showed that compared with GMnC,the improvement effect of wild emmer wheat on GFeC and GZnC in the common wheat background was more significant.Correlation analysis showed that there was no significant negative correlation between the three micronutrient concentrations and TKW.It can be seen that the high GFeC and GZnC characteristics of wild emmer wheat can be transferred into common wheat and can be further transfer and expression in the common wheat background,so that the micronutrient concentrations and yield of the grain were improved simultaneously.3.Phenotypic analysis of 6 main agronomic traits in introgression lines derived from wild emme: Overall,the plant height of the introgression lines populations were significantly lower than those of the wild parents,at the middle(90-100 cm)and middle-high(100-110 cm)levels,and it was significantly positively correlated with the number of tiller and TKW.The number of tillers,spikelets and TKW of the introgression lines populations reached the level of parent CN16.In addition,the mean value of TKW was above 45 g,most materials exceeds the parent CN16(46.80 g).The heading and anthesis date of the introgression lines derived from wild emmer were not significantly different from CN16.4.Population structure and linkage disequilibrium analysis of introgression lines derived from wild emmer D1 and D97: The D1 introgression lines population was mainly divided into three sub-groups,and the D97 introgression lines population was mainly divided into two sub-groups;LD analysis results showed that the LD degree was significantly different between different chromosomes,and the LD decay distance of different genomes was also different.The decay distance of genome D was greater than that of genome A and B.The decay distance of LD in the whole gnome was about 12 c M.5.Association analysis of GPC in introgression lines derived from wild emmer:Based on the consistent results of the general linear model(GLM)and the mixed linear model(MLM),a total of 27 important MTAs related to GPC were detected in the introgression line population,of which 18 MTAs may be new loci of high GPC.Based on these MTAs,a total of 40 candidate genes related to GPC were presumed.These genes may play an important role in conferring higher protein content in wheat grains.6.Association analysis of grain micronutrients concentration(GFeC,GZnC,GMnC)in introgression lines derived from wild emmer: Based on the consistent results of the general linear model(GLM)and the mixed linear model(MLM),a total of 21 important MTAs related to GFeC,GZnC,and GMnC were detected in the introgression lines population,16 of which were new loci.These MTAs have no negative impact on TKW and will promote the development of varieties with high micronutrient concentration and TKW.In addition,a total of 44 candidate genes related to micronutrients were presumed in the wild two wheat infiltration line population,and these genes may have a potential role in cereal micronutrient concentration.7.Association analysis of 6 main agronomic traits in introgression lines derived from wild emmer: Based on the consistent results of the general linear model(GLM)and the mixed linear model(MLM),a total of 195 stable MTAs related to plant height,number of tillers,number of spikelets,heading date,anthesis date,and thousand kernel weight were detected in the introgression lines population.Among them,some MTAs related to the heading date and anthesis date were clustered on 2B and 5B chromosomes.In addition,a total of 31 candidate genes related to agronomic traits were presumed in the introgression lines population.8.Based on the results of phenotypic data and genome-wide association analysis,24 carrier materials with high protein,iron,zinc,manganese loci and excellent agronomic traits were screened out.These carrier materials are expected to be used as common wheat variety resources with high quality and high yield characteristics of wild emmer wheat,which will lay a good foundation for the breeding of high yield and high quality wheat varieties.