| Absract: Wheat is one of the most important crops in the world.High yield,good quality and resistance to diseases are the objectives of wheat breeding.Wheat varieties Ningmai 9and Yangmai 158 play important roles in wheat breeding in the middle and lower reaches of the Yangtze River,which is the second largest wheat region in China.In the past ten years,nearly 80% of the varieties released in national and provincial variety tests have the genetic background of Ningmai 9 or Yangmai 158,indicating that they would be new backbone parents in the future breeding.To make better use of these two parents,the genetic mechanism of their traits need to be further characterized.In this study,282 recombinant inbred lines(RILs)from Ningmai 9 and Yangmai 158 were used as materials to construct a high-density genetic map by wheat illumina 90 k.The yield traits,plant height,heading date and FHB resistance level of the 282 RILs were recorded in multi-environments,and QTL mapping was carried out based on the genotype and phenotype data.For the stable loci,genetic effect analysis,molecular marker development and preliminary verification were further performed.Through this study,the main results are as follows:(1)A genetic map including 2285 bin markers with total length of 3002.1 cM was obtained.This map included 41 linkage groups covering all 21 chromosomes.The mean distance between two markers ranged from 0.65 to 4.09 cM,with a mean of 1.31 cM.The marker ordering of the map produced here was highly consistent with the physical map of the IWGSC Reference Sequence.(2)Both Ningmai 9 and Yangmai 158 showed moderate resistance to FHB,and Ningmai 9 is a little better than Yangmai 158.The FHB resistance level in the RIL population showed great variation,the lowest percentages of scabbed spikelets(PSS)was less than 10%,while in the most seriously affected lines,the PSS were almost all above 50%.The PSS differed in different genotypes,years and locations,.A total of 10 QTLs were identified.Among them,QFhb-3B.1 from Ningmai 9 might be Fhb1 and QFhb-5A fromYangmai 158 was a novel QTL which was not previously described.Distribution of QFhb-5A was tested with a KASP marker closely linked to QFhb-5A.The results suggest that QFhb-5A has undergone both natural and artificial selection,and might be originated from the Italian wheat germplasm.Seven resistant lines were selected out by marker assisted selection and could be used in further FHB resistance breeding.(3)In the three environments,the kernel number per spike of Ningmai 9 was higher than Yangmai 158,thousand grain weight was lower than Yangmai 158,while the spike number and yield were inconsistent in different environments.The environment had significant influence on the above 4 traits,while the interaction between genotype and environment had no significant influence.The spike number and yield were positively correlated with each other in different environments,and thousand grain weight was negatively correlated with the kernel number per spike and positively correlated with yield.The number of QTLs controlling spike number,kernel number per spike,thousand grain weight and yield were 9,8,10 and 12,respectively.The heritability of thousand grain weight was high,which was suitable for genetic selection in breeding programs.After analyzing the genetic effect of the 3 stable QTLs for thousand grain weight,the combination of Qtkw-1B and Qtkw-4A showed the best selection efficiency,which could be applied in wheat genetic improvement for thousand grain weight.(4)The internode length,ear length and plant height of Yangmai 158 were all higher than Ningmai 9,which were significant affected by genotype,environment and their interactions.Based on the phenotype in 3 environments,6 chromosome intervals were identified,and the KASP markers suitable for large-scale screening were successfully developed.After preliminary verification,the combination of Qph-2D and Qph-5A.1 showed the highest selection efficiency for plant height,which might be decreased if further importing Q2 A.It suggests that the selection of Q2 A and Q5 A should mainly focus on the alleles reducing plant height,and Qd1-5D could be used in marker-assisted selection for internode length below spike(D1).(5)The heading date of Ningmai 9 was earlier than Yangmai 158,and showed a difference of 7-11 d in the RIL population in different environments.Genotype,year,location and the interaction between genotype and year all had significant influence on heading date.A total of 26 QTLs controlling heading date were detected,and the phenotypic variance explained(PVE)ranged from 2.50% to 11.91%.Qhd-2B.2,Qhd-3B and Qhd-5A.2 were detected in multiple environments,and their PVE was also relative high.Qhd-5A.2 was the most significant and stable QTL,and the combination of Qhd-2B.2 and Qhd-5A.2 showed thehighest selection efficiency for heading date,and showed no improvement if further importing Qhd-3B.(6)We found 10 QTL-clusters by position alignment.Some QTLs controlled both yield traits and heading date,some controlled both heading date and FHB resistance,and some had effects on yield traits,plant height,and FHB resistance,but the favorable alleles might from different parents.For the QTL with favorable alleles from the same parent,a few markers can be used for selection.For the QTL with favorable alleles from different parents,on one hand,the selection should be in accordance with the breeding target,and on the other hand,the breeding population should be expanded to break linkage drag and use multiple markers for selection. |
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