Construction Of Near-isogenic Introgression Lines For Importantly Agronomic Traits And QTL Analysis In Hexaploid Wheat

Wheat is one of the most important crops in the word, occupying 17%(one sixth) of crop acreage worldwide,feeding about 40% (nearly half) of the world population,and providing 20% (one fifth) of total food calories and protein in human nutrition.The most promising approach to increase agricultural productivity and to satisfy human needs in the future is the genetic improvement of crops, which requires a continuous allocation of new sources of genetic variation.Morden common wheat genetics diversity has been narrowed by modern breeding program,so it is difficult to increase crop yield.Wheat wild species often contain lots of elite alleles that may improve common wheat agronomic characters.It is beneficial to broaden common wheat genetical diversity to exploring and using elite alleles of wild specie.Because agriculturally desirable alleles for yield are often masked by the effects of deleterious alleles and hence cannot be identified phenotypically in the wild germplasm. The advanced backcross quantitative trait locus (AB-QTL) analysis was developed to identify and select new and beneficial QTL alleles of exotic ancestors for introducing elite alleles into gene pool.The Chinese commercial variety Laizhou953 was used as recurrent parent,Am3,a synthetic wheat from crossing Triticum carthlicum accession PS5 and Aegilops tauschii accession Ae38 was used as donor parent.The BC5F4 population were used in this study.Some introgression segments were detected by SSR makers,and conducted QTL analyses for major agronomic traits using these introgression lines.The results obtained were as follow:1.Among 651 pairs of primers that can amplify successfully in two parents,198 pairs were polymorphic markers between two parents,represented 30.4% of total,three(barc1031,barc1057,barc1039) markers haven't mapped in any chromosome,other 39 markers haven't integrated in consensus map.Each chromosome contained 4-15 polymorphic markers,with an average of 9.4 markers for each chromosome.The distance between markers was 11.1cM. Polymorphic markers did not evenly distribution on chromosome among the 21 linkage groups..Marker on 2B chromosome was most,with the total number of 15.Marker on 4D chromosome was least,with the total number of 4.The polymorphic markers also did not evenly distribution in seven homologous groups,most of polymorphic markers detected in the second homologous,with the total number of 45,followed by the fifth homologous group with the total number of 35,and least in the fourth and sixth homologous groups with the total number of 18.2.The results performed by 198 ploymorphic markers in two parents showed that 92 plants from 15 introgression lines all contain donor parents segments,and each introgression lines had a different segments,IL5 detected the most introgression segments,and 13 fragments were detected,IL4 detected the least introgression segments,and 6 fragments were detected.Twenty markers segregated in introgression lines population,13 of 20 markers located in 5B,7B,7D chromosomes,the others 7 markers,barc128,wmc128,gdm33,wms637,wms357,wms102,wms372 located in 1A,1B,2A,2D,4A chromosomes respectively.3.When the object of study is lines, there were 3 to 6 traits that are significant different from recurrent parent Laizhou953each introgression lines contained. Lots of itrogressed segments were beneficial for agronomic traits, especially for spike length and spikelets.12 of 15 introgression lines'grain number of spikelet were more than recurrent parent,which indicated that there were correlation relationship among spike legth,spikelet,and grain number of spikelet.4.One-way ANOVA analysis was used to detected QTL for six argonomic traits,in total 11 putative QTLs loci were detected for spike length,spikelet,grain number of spikelet and thousand grains weight,one of the all detected QTLs,which located in 7B chromosome,has a large additive effects, additive effects percent rate is 5.08%, two loci that control two traits simultaneously were detected,additive effects of barc255 locus was 2.42 for grain number of spikelet,and was-1.74 for thousand grain weight,which was negative and represented allele from donor parent reduce thousand grain weight.Additive effects of wmc662 loci was 2.54 for grain number of spikelet,was 1.56 for thousand grain weight.Two QTLs were detected bsy using software QTLNetwork-2.0,one located in 7B chromosome for grain number of spikelet,between wmc76 and wmc476,the genetics distance is 11.1 cM. The other one also located in 7B chromosome for spikelet,between wmc662 and wmc76,the genetics distance is 42 cM.6 QTLs for spike and grain number of spikelet were detected by two-ways ANOVA based on datas from two years, spikelet and grain number of spikelet both were affected by environment, QTL for grain number of spikelet of wms297 locus was affected by genotype and environment interaction, QTL for spikelet of wmc76 locus was affected by genotype and environment interaction.