Grain number per spike(GNPS) is a major factor in wheat yield breeding.A new wheat germplasm Pubing 3504 shows superior features in spike traits.To elucidate the genetic basis of spike and yield related traits in Pubing 3504,282 F2:3 families were generated from the cross Pubing 3504×Jing 4839,and seven spike and yield related traits,including GNPS,spike length(SL),kernel number per spikelet(KPS),spikelet number per spike(SNS),thousand-grain weight(TGW),spike number per plant(SNP),and plant height(HT) were investigated.Correlation analysis indicated significant positive correlations between GNPS and spike-related traits,including KPS,SNS,and SL,especially KPS.A genetic map was constructed using 190 polymorphic simple sequence repeat(SSR),expressed sequence tag(EST)-SSR,and sequencetagged-site(STS) markers.For the seven traits measured,a total of 37 quantitative trait loci(QTLs) in a single-environment analysis and 25 QTLs in a joint-environment analysis were detected.Additive effects of 70.3%(in a single environment) and 57.6%(in a joint environment) of the QTLs were positively contributed by Pubing 3504 alleles.Five important genomic regions on chromosomes 1 A,4 A,4 B,2 D,and 4 D could be stably detected in different environments.Among these regions,the marker interval Xmag834–Xbarc83 on the short arm of chromosome 1 A was a novel important genomic region that included QTLs controlling GNPS,KPS,SNS,TGW,and SNP with stable environmental repeatability.This genomic region can improve the spike trait and may play a key role in improving wheat yield in the future.We deduced that this genomic region was vital to the high GNPS of Pubing 3504.
Grain number per spike (GNPS) is a major factor in wheat yield breeding. The development of high GNPS germplasm is widely emphasized in wheat-yield breeding. This paper reported two high GNPS wheat germplasm lines, Pubing 3228 and Pubing 3504, which had a stable and wide adaptability to different ecological regions. By exploring a nested cross design with reciprocals using Pubing 3228 or Pubing 3504 as a common parent and investigating the GNPS phenotypes of F 1 hybrids in 2007-2008 and F 2 populations in 2008-2009 of different cross combinations, the narrow-sense GNPS heritability was up to 49.58 and 52.23%, respectively. Genetic model analysis predictions suggested that GNPS in Pubing 3228 and Pubing 3504 was mainly controlled by additive genetic effects. Correlation analysis results between GNPS and 1 000- kernel weight (TKW) of F 2 populations showed that TKW was not influenced with the increase of GNPS. The good coordination among three yield components of spike number per plant (SNPP), GNPS, and TKW in the F 2 segregating population implied that selection of good candidate individuals in breeding programs would be relatively straightforward. Overall, our results indicated that Pubing 3228 and Pubing 3504 are two potential germplasm lines for yield improvement of GNPS in pedigree selection of wheat breeding.
Founder parents have contributed significantly to the improvement of wheat breeding and production. In order to investigate the genetic characteristics of founder parents and widely planted cultivars, Mazhamai(M), Biyumai(B) and six sibling lines(BM1–6) derived from the cross M×B were phenotyped for eight yield-related traits over multiple years and locations and genotyped using the the wheat 90 K single nucleotide polymorphism(SNP) assay. BM4 has been used as a founder parent, and BM1 has been widely planted, whereas BM2, 3, 5, and 6 have not been used extensively for breeding or planting in China. Phenotypic comparisons revealed that BM4 and BM1 displayed a better overall performance than the other sibling lines. BM1 showed higher thousand-grain weight than BM4, whereas BM4 exhibited lower coefficient of variation for most of the yield-related traits across different years and locations, indicating that BM4 was widely adaptable and more stable in different environments. SNP analysis revealed that BM4 and BM1 inherited similar proportions of the M genome but are dissimilar to BM2, 3, 5, and 6. Both BM1 and BM4 have specific alleles that differ from the other BM lines, and most of these alleles are concentrated in specific chromosomal regions that are found to associate with favorable QTLs, these SNPs and their surrounding regions may carry the genetic determinants important for the superior performance of the two lines. But BM4 has more genetic diversity than BM1 with more specific alleles and pleiotropic regions, indicating that the genome of BM4 may be more complex than the other sibling lines and has more favorable gene resources. Our results provide valuable information that can be used to select elite parents for wheat and self-pollinating crop breeding.
The wheat grain number per spike(GNPS)is a major yield-limiting factor in wheat-breeding programs.Germplasms with a high GNPS are therefore valuable for increasing wheat yield potential.To investigate the molecular characteristics of young spike development in large-spike wheat germplasms with high GNPS,we performed gene and protein expression profiling analysis with three high-GNPS wheat lines(Pubing 3228,Pubing 3504 and 4844-12)and one low-GNPS control variety(Fukuho).The phenotypic data for the spikes in two growth seasons showed that the GNPS of the three large-spike wheat lines were significantly higher than that of the Fukuho control line.The Affymetrix wheat chip and isobaric tags for relative and absolute quantitation-tandam mass spectrometry(iTRAQ-MS/MS)technology were employed for gene and protein expression profiling analyses of young spike development,respectively,at the floret primordia differentiation stage.A total of 598 differentially expressed transcripts(270 up-regulated and 328 down-regulated)and 280 proteins(122 upregulated and 158 down-regulated)were identified in the three high-GNPS lines compared with the control line.We found that the expression of some floral development-related genes,including Wknox1b,the AP2 domain protein kinase and the transcription factor HUA2,were up-regulated in the high-GNPS lines.The expression of the SHEPHERD(SHD)gene was up-regulated at both the transcript and protein levels.Overall,these results suggest that multiple regulatory pathways,including the CLAVATA pathway and the meristem-maintaining KNOX protein pathway,take part in the development of the high-GNPS phenotype in our wheat qermplasms.
