Fa Cui

Conditional QTL mapping for plant height with respect to the length of the spike and internode in two mapping populations of wheat.

Plant height (PH) in wheat is a complex trait; its components include spike length (SL) and internode lengths. To precisely analyze the factors affecting PH, two F8:9 recombinant inbred line (RIL) populations comprising 485 and 229 lines were generated. Crosses were performed between Weimai 8 and Jimai 20 (WJ) and between Weimai 8 and Yannong 19 (WY). Possible genetic relationships between PH and PH components (PHC) were evaluated at the quantitative trait locus (QTL) level. PH and PHC (including SL and internode lengths from the first to the fourth counted from the top, abbreviated as FIITL, SITL, TITL, and FOITL, respectively) were measured in four environments. Individual and the pooled values from four trials were used in the present analysis. A QTL for PH was mapped using data on PH and on PH conditioned by PHC using IciMapping V2.2. All 21 chromosomes in wheat were shown to harbor factors affecting PH in two populations, by both conditional and unconditional QTL mapping methods. At least 11 pairwise congruent QTL were identified in the two populations. In total, ten unconditional QTL and five conditional QTL that could be detected in the conditional analysis only have been verified in no less than three trials in WJ and WY. In addition, three QTL on the short arms of chromosomes 4B, 4D, and 7B were mapped to positions similar to those of the semi-dwarfing genes Rht-B1, Rht-D1 and Rht13, respectively. Conditional QTL mapping analysis in WJ and WY proved that, at the QTL level, SL contributed the least to PH, followed by FIITL; TITL had the strongest influence on PH, followed by SITL and FOITL. The results above indicated that the conditional QTL mapping method can be used to evaluate possible genetic relationships between PH and PHC, and it can efficiently and precisely reveal counteracting QTL, which will enhance the understanding of the genetic basis of PH in wheat. The combination of two related populations with a large/moderate population size made the results authentic and accurate.

Molecular cytogenetic characterization of a new wheat-Thinopyrum intermedium partial amphiploid resistant to powdery mildew and stripe rust.

A partial amphiploid, TE253, derived from crosses between the common wheat (Triticum aestivum L.) cultivar Yannong 15 and Thinopyrum intermedium (Host) Barkworth & D.R. Dewey was characterized by cytogenetic observations, disease resistance tests and genomic in situ hybridization (GISH). Mitotic observations showed that most plants of TE253 had 56 chromosomes, but a few had 54 or 55 chromosomes. The chromosomes in most pollen mother cells of plants with 2n = 56 formed 28 bivalents. Univalents (0.89 per cell) and tetravalents (0.087 per cell) occasionally occurred at meiotic metaphase I, showing a high degree of cytogenetic stability. After inoculation with the powdery mildew and stripe rust pathogens, Yannong 15 was highly susceptible, whereas TE253 and Th. intermedium were immune to both diseases. This indicated that the resistance of TE253 to powdery mildew and stripe rust was derived from Th. intermedium. GISH analysis using St-genomic DNA from Pseudoroegneria strigosa (M. Bieb) Á. Löve as a probe and ABD-genomic DNA from Chinese Spring wheat as a blocker demonstrated that TE253 consisted of 2 St-genome chromosomes, 8 JS-genome chromosomes, 2 SAT J chromosomes and 2 J-St translocated chromosomes. Line TE253 is a new partial amphiploid with resistance to both powdery mildew and stripe rust and can be used as a source of resistance genes in wheat improvement.

QTL detection of seven quality traits in wheat using two related recombinant inbred line populations

Grain protein content (GPC) and gluten quality are the most important factors determining the end-use quality of wheat for pasta-making. Both GPC and gluten quality are considered to be polygenic traits influenced by environmental factors and other agricultural practices. Two related F8:9 recombinant inbred line (RIL) populations were generated to localise genetic factors controlling seven quality traits: GPC, wet gluten content (WGC), flour whiteness (FW), kernel hardness (KH), water absorption (Abs), dough development time (DDT) and dough stability time (DST). These lines were derived by crossing Weimai 8 and Jimai 20 (WJ) and by crossing Weimai 8 and Yannong 19 (WY). In total, WJ comprised 485 lines, while WY comprised 229 lines. Data on these seven quality traits were collected from each line in five different environments. Up to 85 putative QTLs for the seven traits were detected in WJ and 65 putative QTLs were detected in WY. Of these QTLs, 31 QTLs (36.47%) were detected in at least two trials in WJ, while 24 QTLs (36.92%) were detected in at least two trials in WY. Three QTLs from WJ and 25 from WY accounted for more than 10% of the phenotypic variance. The total 150 QTLs were spread throughout all 21 wheat chromosomes. Of these, at least thirteen pairwise were common to both populations, accounting for 20.00 and 15.29% of the total QTLs in WJ and WY, respectively. A major QTL for GPC, accounting for 53.04% of the phenotypic variation, was detected on chromosome 5A. A major QTL for WGC also shared this interval, explained more than 36% of the phenotypic variation, and was significant in two environments. Though co-located QTLs were common, every trait had its unique control mechanism, even for two closely related traits. Due to the different sizes of the two line populations, we also assessed the effects of population size on the efficiency and precision of QTL detection. In sum, this study will enhance our understanding of the genetic basis of these seven pivotal quality traits and facilitate the breeding of improved wheat varieties.

Transmission of the Chromosome 1R in Winter Wheat Germplasm Aimengniu and Its Derivatives Revealed by Molecular Markers

In order to clarify the transmission of the rye chromosome 1R in winter wheat germplasm Aimengniu and its derivatives, 17 derivatives and 7 types of Aimengniu were examined through molecular-marker technology. The results showed that the chromosome arm 1RS of Neuzucht was transmitted to 5 of the 7 types of Aimengniu, i.e., Aimengniu II and Aimengniu IV-Aimengniu VII, no segment of 1RS was identified in Aimengniu I or Aimengniu III. As for the 17 derivatives, the 1RS chromosome arm of Aimengniu was transmitted to 11 derivatives, part segments of 1RS were found in 1 derivative, while no segment was found in the remaining 5 ones. The results provided the evidence that molecular-marker technology was an efficient approach and suitable for analysis of the transmission of chromosome 1R.

Mapping QTLs for Yield Related Traits Using Two Associated RIL Populations of Wheat

Abstract The objectives of this study were to map quantitative trait loci (QTLs) for yield related trait in wheat ( Triticum aestivum L.) grown in multiple environments, identify chromosomal regions harboring important loci, and validate the stability of these chromosomal regions in different environments. The QTLs for spikelet number per spike (SN), grain number per spike (GN), spike number per plant (PN), 1000-grain weight (GW), and grain yield per plant (GY) were detected using inclusive composite interval mapping method. The 2 mapping populations were the F 8:9 generations of Weimai 8 × Yannong 19 (WY population) and Weimai 8 × Jimai 20 (WJ population), which contained 229 and 485 lines, respectively. Both populations were grown in 4 environments. Numerous QTLs for the 5 traits were identified on 21 chromosomes of wheat, including 9 for SN, 9 for GN, 4 for PN, 7 for GW, and 5 for GY in the WY population and 20 for SN, 16 for GN, 11 for PN, 14 for GW, and 9 for GY in the WJ population. Sixteen and 3 major QTLs with the phenotypic contribution larger than 10% were detected in the WY and WJ populations, respectively. In addition, 5 and 17 QTLs were identified in at least 2 environments in the WY and WJ populations, respectively. Some QTLs were mapped in the same or closely linked marker intervals in both populations. Nine pairs of QTLs and 2 chromosomal regions were inferred to be identical between the 2 populations. These results may enrich the QTL information for yield components of wheat and facilitate marker-assisted selection.

QTL Detection of Internode Length and its Component Index in Wheat Using Two Related RIL Populations

To comprehensively understand the genetic basis of plant height (PH), quantitative trait locus (QTL) analysis for internode lengths, internode component indices and plant height component index (PHCI) were firstly conducted in the present study. Two related F8:9 recombinant inbred line (RIL) populations comprising 485 and 229 lines were used. Two hundred and nine putative additive QTL for the eight traits were identified, 35 of which showed significance in at least three trials. Of these, at least 11 pairwise QTL were common to the two populations. PH components at the QTL level had different effects on PH, confirming our previous multivariate conditional analysis (Cui et al. 2011). Eleven major QTL that showed consistency in expression across environments should be of great value in the genetic improvement of PH in wheat. The results above will enhance the understanding of the genetic basis of PH in wheat.

Length of internode and spike: How do they contribute to plant height of wheat at an individual QTL level?

A recombinant inbred line (RIL) population with 302 lines derived from a cross of Weimai 8 × Luohan 2 was used to identify the quantitative trait loci (QTL) for plant height (PH) in wheat (Triticum aestivum L.). Possible genetic relationships between PH and PH components (PHC), including spike length (SL) and internode length from the first to the fourth node counted from the top, abbreviated as FIITL, SITL, TITL and FOITL, respectively, were evaluated at the QTL level. A QTL for PH was mapped using data on PH and on PH conditioned by PHC using the IciMapping V3.0 software. Conditional QTL mapping proved that, at the QTL level, SL contributed the least to PH, followed by FIITL and FOITL, while TITL had the strongest influence on PH, followed by SITL. These results indicate that the conditional QTL mapping method can be used to evaluate possible genetic relationships between PH and PHC, and that it can efficiently and precisely reveal counteracting QTL, which will enhance our understanding of the genetic basis of PH in wheat.

QTL Mapping for Grain Yield Conditioned on its Component Traits in Two RIL Populations of Bread Wheat

Grain yield (GY) and yield components (YC) were investigated using two F8: 9 RILs, comprising 229 and 485 lines, respectively. A conditional analysis was conducted to generate conditional values for GY independent of each YC. Then both unconditional and conditional values were analyzed to map QTLs with additive effect. In both RILs, up to 23 unconditional and conditional QTLs were detected. However, only two QTLs were identified repeatedly among environments. All QTLs, except for 4 detected in unconditional mapping, were also identified as conditional QTLs, whereas a number of QTLs were additionally detected in conditional mapping. The number of QTLs detected that affected GY was different with respect to component-special influences. Our results revealed that the contributions of YC influencing QTL expression related to GY differed.

Genetic Differences in Homoeologous Group 1 of Seven Types of Winter Wheat Aimengniu

Abstract Aimengniu (hereafter AMN), cultivated by Shandong Agricultural University, is a renowned Chinese winter wheat germplasm. The purpose of this study was to dissect the genetic difference among the 7 AMN-derived types in homoeologous group 1. The translocation between chromosomes 1B and 1R was identified in the 7 AMN-derived types (AMNI to AMNVII) using molecular markers and genomic in situ hybridization (GISH). Amplified with the specific primers for 1R and 1B, the AMNI and AMNIII plants showed the presence of normal 1B chromatin, and the remaining types had both 1RS and 1BL but not 1BS and 1RL chromatin. The GISH result confirmed the replacement of 1BS by 1RS in AMNII, AMNIV, AMNV, AMNVI, and AMNVII plants; and the typical common wheat karyotype was observed in AMNI and AMNIII plants. In addition, genetic differences among the 7 AMN-derived types in homoeologous group 1 were detected using 138 polymorphic markers. Three markers, Xwmc336 and Xmag1884 on chromosome 1A and Xgwm124 on chromosome 1B, amplified specific segments of AMNV. Loci of Xwmc336 and Xmag1884 originated from the parent Neuzucht and that of Xgwm124 from the parent Aifeng 3.

Genetic Difference of Sib lines Derived from Winter Wheat Germplasm “Aimengniu”

Abstract “Aimengniu” (Aifeng 3//Mengxian 201/Neuzucht) is a backbone parent for cultivar improvement of winter wheat (Triticum aestivum L.) in China. Up to 2007, 26 wheat cultivars have been developed from the crosses using Aimengniu as a parent. To disclose the genetic basis of this backbone parent in breeding process, the genetic and phenotypic differences among 7 Aimengniu-derived sib lines (types) were compared based on the results from 656 molecular markers and 16 agronomic traits. There were obvious variations among the 7 Aimengniu-derived types in the traits surveyed. The Aimengniu-derived type V showed better performance on yield components than other types. A graphical genotype integrated map was constructed using the molecular marker data, which showed the inheritance of fragments from the 3 parents to Aimengniu. Two F2 populations (Aifeng 3/Neuzucht and Mengxian 201/Neuzucht) were developed to identify quantitative trait loci (QTLs) for yield-related traits in the Aimengniu-derived type V. Eight loci specific to Aimengniu type V were detected on chromosomes 1A, 1B, 2D, 3A, 4D, and 7A, which were associated with QTLs for yield components. These specific loci might discriminate the type V from other types at genomic level.