Genetic Dissection Of FHB Resisitance And Major Agronomic Traits In Wheat Germplasm C615 And Development Of A KASP Marker For Waxy Allele Wx-D1d

Common wheat(Triticum aestivum L.)is one of the most important crops worldwide.Development and application of high yielding cultivars plays important roles in wheat production.However,since extensive use of minority of wheat parents with high-yielding,good quality and highly adversity-resistance in breeding,genetic narrowing of modern cultivars has becomes a key factor limiting further improvement of wheat.Wheat germplasm C615 introduced from International Maize and Wheat Improvement Center(CIMMYT)not only contains abundant genetic variation and but also has many elite traits such FHB resistance,probably mainly because its parents involved a synthetic wheat.Thus it is very necessary to understand its genetic structure and identify the beneficial genes.Additionally,along with the improved living standard of Chinese,continuous improvement of end-use quality of wheat cultivars remains important for development and use of waxy wheat since it was developed in 1995 because of its unique starch properties.The present resrach included three parts,the first part one involved the identification and mapping of QTLs controlling Fusarium head blight(FHB)resistance and major agronomic traits using a RIL population derived from C615/Yangmai 13;The second one involved development of a series of C615 chromosome segment introgression lines(CSSLs)in the background of Yangmai 13 by backcrosses and marker assisted selection(MAS),where the genetic basis of eight major traits were evaluated;The third one involved the development and utilization of a KASP marker for Wx-D1d allele in waxy wheat K107wx1.The main results were as follows:1.The high-density linkage map was based on the genotypic data from 90 K arrays derived from the cross of-C615/Yangmai 13.The linkage map corresponding to 21 wheat chromosomes was constructed from 4017 polymorphic SNP markers and overall marker density was 0.65 markers per cM.The whole linkage map covered 2620.9 cM,with an average chromosome length of 124.8 cM,and the length individual chromosome ranged from 30.7 cM(4D)to 179.9 cM(4A).Both the map length and polymorphic marker number were unequally distributed in the three genomes of wheat,where A-genome chromosomes have the largest length and marker number(1017.2 cM and 1898 SNPs),followed by B-genomes chromosomes(926.2 cM and 1452 SNPs),while D-genome chromosomes were the smallest(677.5 cM and 667 SNPs).Based on the genotyping and phenotyping data of this population,total 62 QTLs controlling seven traits such as FHB resistance,PH(plant height),SL(spike length),SNS(spikelet number per spike),SC(spikelet compactness),HD(heading day)and FD(flowering day)were detected on 21 chromosomes excluding 4D and 7B after CIM(complex interval mapping)analysis.(1)In the point inoculated experiments(Yangzhou),eight Type II QTL were identified on chromosomes 1AS,1BL,2DS,2DL,4AL,5AL,5DL and 6AS,and explained 4.25-11.79%of the phenotypic variance,respectively.The resistance alleles such as QFhbpoint.yaas-2DS-1,QFhbpoint.yaas-2DL-1,QFhbpoint.yaas-4AL-1 and OFhbpoint.yaas-5DL-1 were from parent C615.In the spray inoculated experiments(Yangzhou),six QTL were mapped on chromosomes 1AS,1AL,2AL,2DL,4AL and 6AS,and explained 5.43-9.61%of the phenotypic variance,respectively.Resistance alleles at five loci were come from parent C615.In the natural infected experiments(Jianyang),five QTL were located on chromosomes 2BL,2DL,4AL,5BL and 7AL,and explained 4.84-10.48%of the phenotypic variance,respectively.Among them,QFhbnatural.yaas-2BL-1 was explained 10.48%of the mean phenotypic variance.(2)11 QTL for PH were identified on chromosome 1AL,IDS,2DS,3AL,3BL,4AL,4BL,5AL,5BL and 6AS,and explained 4.23-11.25%of the phenotypic variance,respectively.Of them,two QTL,QPh.yaas-1AS.1 and QPh.yaas-5BL-1 were stably across four environments,and explained 6.32%and 5.27%of the mean phenotypic variance,respectively.(3)22 QTL for spike-related traits were detected in all environments.Among them,eight for SL were mapped on chromosomes 3AL,3BS,4AS,4B,5AL(2),6BS and 7DS,explained 5.31-12.55%of the phenotypic variance,respectively;nine for SNS were on chromosomes 1AS,1AL,2DS,2DL,3B,4AS,4AL,5AL and 6BS,explained 4.44-12.10%of the phenotypic variance,respectively;five for SC were on chromosomes 2BS,3AL,3BS,5AL and 5BL,explained 4.71-17.36%of the phenotypic variance respectively.Two QTL on 3BS and 5AL were pleiotropic for SL,SNS and SC.(4)Six QTL for HD were mapped on chromosome 2BS,3AS,3DS,4AS,6DS and 7AS,and explained 4.88-15.50%of the phenotypic variance,respectively.QHd.yaas-4AS-1 was stable across three environments,explaining 11.79%of the mean phenotypic variance,respectively.Five QTL for FD were mapped on chromosome 2BS,4AS,6AS,6DS and 7AS,and explained 5.05-13.50%of the phenotypic variance,respectively.2.A set of CSILs covering the entire genome of the donor C615 were developed from the cross Yangmai 13*5/C615 where Yangmai 13 was the recurrent parent based on molecular marker selection using 197 polymorphic SSR markers.The CSILs consisted of 100 different lines with 3.83 introgressed segments per line at average.Of the CSILs,nine carried a single introgressed segment and two involved 22 ones.For the introgressed homozygous segments,the length of introgressed segments ranged from the shortest 3.5 cM to the longest 50.3 cM with an average of 33.3 cM.The mean recipient genome composition(RGC)of the CSILs was 97.52%,the absent segments were mainly located in the terminal and cnetromeric regions of chromosomes.The length of whole absent segment was 103 cM,ranging from the shortest 2.0 cM(6A)to the longest 18.0 cM(3A).Using the CSILs,total eight traits including FHB resistance,PH,SL,SNS,SC,HD,FD,thousand-kernel weight(TKW)were evaluated.Investigation of FHB resistance in Yangzhou and Jianyang found five CSILs such as CSIL25,CSIL60,CSIL74,CSIL77 and CSIL89 showed resistance better than Yangmai 13.The mean value of eight traits of all the CSILs are closer to Yangmai 13 where all traits involved some CSILs quite superior than the two parents.This result revealed that the CSILs involved abundant genetic variation,which provides very useful genetic materials for both genetic study of C615 and wheat breeding.3.The waxy wheat line K107Wxl was developed by treating Kanto 107 seeds with ethyl methanesulphonate(EMS),which carries the Wx-D1d allele.However,no molecular basis supports this nomenclature.In the present study,DNA sequence analysis confirmed that a single nucleotide polymorphism(SNP)at 1484 bp in the sixth exon of Wx-D1,changed tryptophan(TGG)into a termination codon.Based on this sequence variation,a PCR-based KASP marker was thus developed for detecting this point mutation using BC8F1 plants derived from the cross Ningmai 14*9/K107Wx1.Combined with codominant markers for the Wx-A1 and Wx-B1 alleles,waxy and non-waxy near-isogenic lines(NILs)were distinguished.The KASP marker was efficient in identifying the mutant allele,and can be used to transfer waxiness to elite lines.