Quantitative Trait Loci For Yield Components Research Articles

Allelic response of yield component traits to resource availability in spring wheat.

Investigation of resource availability on allele effects for four yield component quantitative trait loci provides guidance for the improvement of grain yield in high and low yielding environments. A greater understanding of grain yield (GY) and yield component traits in spring wheat may increase selection efficiency for improved GY in high and low yielding environments. The objective of this study was to determine allelic response of four yield component quantitative trait loci (QTL) to variable resource levels which were manipulated by varying intraspecific plant competition and seeding density. The four QTL investigated in this study had been previously identified as impacting specific yield components. They included QTn.mst-6B for productive tiller number (PTN), WAPO-A1 for spikelet number per spike (SNS), and QGw.mst-3B and TaGW2-A1 for kernel weight (KWT). Near-isogenic lines for each of the four QTL were grown in multiple locations with three competition (border, no-border and space-planted) and two seeding densities (normal 216 seedsm-2 and low 76 seedsm-2). Allele response at QTn.mst-6B was driven by changes in resource availability, whereas allele response at WAPO-A1 and TaGW2-A1 was relatively unaffected by resource availability. The QTn.mst-6B.1 allele at QTn.mst-6B conferred PTN plasticity resulting in significant GY increases in high resource environments. The gw2-A1 allele at TaGW2-A1 significantly increased KWT, SNS and GPC offering a source of GY improvement without negatively impacting end-use quality. QGw.mst-3B allelic variation did not significantly impact KWT but did significantly impact SPS. Treatment effects in both experiments often resulted in significant positive impacts on GY and yield component traits when resource availability was increased. Results provide guidance for leveraging yield component QTL to improve GY performance in high- and low-yield environments.

Improving hexaploid spring wheat by introgression of alleles for yield component traits from durum wheat

AbstractHexaploid bread wheat (Triticum aestivum L.) and tetraploid durum wheat (Triticum durum Desf.) have been cultivated in similar geographic areas for ∼10,000 yr. The crossing barrier caused by ploidy difference suggests that different favorable alleles for yield‐related traits may have accumulated in the two crops. Previous work allowed identification of favorable alleles at six quantitative trait loci (QTL) from durum wheat in a recombinant inbred line (RIL) population from a cross of ‘Mountrail’ durum and ‘Choteau’ spring wheat. The purpose of this study was to determine the impact of six durum alleles at yield component QTL in several spring wheat backgrounds. Three spring wheat cultivars were crossed with six hexaploid lines derived from the original Choteau/Mountrail cross to generate RILs. Heterozygous RILs, containing both the durum and the bread wheat alleles, were identified for each of the QTL. The heterozygous RILs were used to develop near‐isogenic lines (NILs) for the six introgressed QTL. The NILs were grown in five environments under irrigated and rainfed conditions in Montana in 2017 and 2018. A durum allele QTL on chromosome 3B resulted in increased kernel weight in all five environments. The introgressed durum QTL alleles caused pleiotropic interactions among yield component traits. Environment and genetic background significantly affected the stability of introgressed QTL on yield components for four of the six QTL. Results suggest that alleles from durum may be useful for yield improvement of hexaploid spring wheat. However, interrelationships of yield components, pleiotropic interactions, and environment will affect the value of durum wheat alleles in hexaploid wheat backgrounds.

Linkage disequilibrium mapping for grain Fe and Zn enhancing QTLs useful for nutrient dense rice breeding

BackgroundHigh yielding rice varieties are usually low in grain iron (Fe) and zinc (Zn) content. These two micronutrients are involved in many enzymatic activities, lack of which cause many disorders in human body. Bio-fortification is a cheaper and easier way to improve the content of these nutrients in rice grain.ResultsA population panel was prepared representing all the phenotypic classes for grain Fe-Zn content from 485 germplasm lines. The panel was studied for genetic diversity, population structure and association mapping of grain Fe-Zn content in the milled rice. The population showed linkage disequilibrium showing deviation of Hardy-Weinberg’s expectation for Fe-Zn content in rice. Population structure at K = 3 categorized the panel population into distinct sub-populations corroborating with their grain Fe-Zn content. STRUCTURE analysis revealed a common primary ancestor for each sub-population. Novel quantitative trait loci (QTLs) namely qFe3.3 and qFe7.3 for grain Fe and qZn2.2, qZn8.3 and qZn12.3 for Zn content were detected using association mapping. Four QTLs, namely qFe3.3, qFe7.3, qFe8.1 and qFe12.2 for grain Fe content were detected to be co-localized with qZn3.1, qZn7, qZn8.3 and qZn12.3 QTLs controlling grain Zn content, respectively. Additionally, some Fe-Zn controlling QTLs were co-localized with the yield component QTLs, qTBGW, OsSPL14 and qPN. The QTLs qFe1.1, qFe3.1, qFe5.1, qFe7.1, qFe8.1, qZn6, qZn7 and gRMm9–1 for grain Fe-Zn content reported in earlier studies were validated in this study.ConclusionNovel QTLs, qFe3.3 and qFe7.3 for grain Fe and qZn2.2, qZn8.3 and qZn12.3 for Zn content were detected for these two traits. Four Fe-Zn controlling QTLs and few yield component QTLs were detected to be co-localized. The QTLs, qFe1.1, qFe3.1, qFe5.1, qFe7.1, qFe8.1, qFe3.3, qFe7.3, qZn6, qZn7, qZn2.2, qZn8.3 and qZn12.3 will be useful for biofortification of the micronutrients. Simultaneous enhancement of Fe-Zn content may be possible with yield component traits in rice.

Mapping of quantitative trait loci for root hair length in wheat identifies loci that co-locate with loci for yield components.

Root hairs are fast growing, ephemeral tubular extensions of the root epidermis. They arise in the unsuberized maturation zone of the root, effectively increasing the root surface area in the region over which nutrient and water uptake occur. Variation in root hair length (RHL) between varieties has been shown to be genetically determined, and could, therefore, have consequences for nutrient capture and yield potential in crops. We describe the development of a medium-to-high throughput screening method for assessing RHL in wheat at the seedling stage. This method was used to screen a number of wheat mapping population parental lines for variation in RHL. Parents of two populations derived from inter-varietal crosses differed for RHL: Spark vs Rialto and Charger vs Badger. We identified quantitative trait loci (QTLs) for RHL in the populations derived from these crosses. In Spark × Rialto, QTLs on chromosomes 1A, 2A and 6A were associated with variation in RHL, whilst in Charger × Badger, a QTL for RHL was identified on 2BL. The QTLs on 2A and 6A co-localized with previously described QTLs for yield components. Longer root hairs may confer an advantage by exploiting limiting mineral and water resources. This first QTL analysis of root hair length in wheat identifies loci that could usefully be further investigated for their role in tolerance to limiting conditions.

Genetic Difference of Siblines Derived from Winter Wheat Germplasm “Aimengniu”

采用田间试验鉴定和基因组分子标记分析相结合的方法，对冬小麦种质“矮孟牛” 7个类型的性状和基因组遗传差异比较分析。结果表明，7个类型在调查的株高、穗长、穗粒数、粒长、粒宽、单株穗数等16个性状方面存在差异，其中矮孟牛V型的主要产量构成因素等性状比较协调，总体优于其他6个类型。在检测的2 210对SSR、EST-SSR和STS标记中，有656对标记可在矮孟牛三亲本中显示多态性，将其用于矮孟牛7个类型全基因组遗传差异分析，并利用GGT2.0绘制7个类型的遗传差异图谱。在矮孟牛V型的1A、1B、2D、3A、4D、7A染色体上检测到8个特异位点，利用矮丰3号/牛朱特和孟县201/牛朱特构建的2个F 2 分离群体，经IciMappingV3.0单标记QTL作图分析，发现矮孟牛V型部分特异位点附近存在与产量构成因素等重要性状相关的QTL。矮孟牛V型的基因组特异位点可能是它作为骨干亲本区别于其他姊妹系的重要基因组特征。

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

“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.

Soybean QTL for Yield and Yield Components Associated with Glycine soja Alleles

U.S. soybean [Glycine max (L.) Merr.] germplasm has a narrow genetic base. The objective of this study was to identify G. soja Sieb. and Zucc. alleles for yield and yield component quantitative trait loci (QTL). Two populations of BC2F4 lines were generated from a mating between recurrent parent G. max ‘7499’ and donor parent G. soja PI 245331 with one line in each population tracing back to the same BC2 plant. Population A was used for the QTL identification analysis and Population B was used for the QTL verification test. The Population A lines were genotyped at 120 simple sequence repeat marker loci and one phenotypic marker locus. There were 11 putative QTL significantly associated with yield and yield component traits across three environments. One QTL for seed yield was found using the combined data. At this locus, the G. soja allele at Satt511 on LG A1 was associated with increased seed yield with an additive yield effect of 191 to 235 kg ha−1 depending on the QTL analysis method. Across environments in the validation population, lines that were homozygous for the G. soja allele at Satt511 demonstrated a 6.3% yield increase over lines that were homozygous for the G. max allele. One seed filling period QTL was identified on LG F with an additive effect of +1 d. This QTL also provided a +1 d additive effect on maturity. These results demonstrate the potential of identifying positive alleles in the exotic germplasm of soybean.

Evidence for Colinearity among Genetic Linkage Maps in Cucumber

Cucumber (Cucumis sativus L. var. sativus; 2n = 2x = 14), has a narrow genetic base (3% to 8% polymorphism). Nevertheless, several genetic maps exist for this species. It is important to know the degree of colinearity among these maps. Thus, the positions of random amplified polymorphic DNAs, sequenced characterized amplified regions, simple sequence repeat, restriction fragment length polymorphisms, and fluorescent amplified fragment length polymorphism markers were compared in four maps. A previously unreported map was constructed in a narrow cross (processing line 2A × Gy8; C. s. var. sativus; ≈7% polymorphism) and compared with the three published maps [two narrow-based (processing type; C. s. var. sativus; 8% to 12% polymorphism) and a broad-based (C. s. var. sativus × C. s. var. hardwickii (R.) Alef. ≈12%)]. Common makers were identified in seven linkage groups, providing evidence for microsynteny. These common markers were used as anchor markers for map position comparisons of yield component quantitative trait loci. The relative order of anchor markers in each of six linkage groups (linkage groups 1, 2, and 4–7) that had two or more anchor markers within each group was colinear, and instances of microsynteny were detected. Commonalities in the position of some yield component quantitative trait loci exist in linkage groups 1 and 4 of the maps examined, and the general synteny among these maps indicates that identification and mapping of additional anchor markers would lead to successful map merging to increase cucumber map saturation for use in cucumber breeding.

Construction of two BAC libraries from cucumber (Cucumis sativus L.) and identification of clones linked to yield component quantitative trait loci

Two bacterial artificial chromosome (BAC) libraries were constructed from an inbred line derived from a cultivar of cucumber (Cucumis sativus L.). Intact nuclei were isolated and embedded in agarose plugs, and high-molecular-weight DNA was subsequently partially digested with BamHI or EcoRI. Ligation of double size-selected DNA fragments with the pECBAC1 vector yielded two libraries containing 23,040 BamHI and 18,432 EcoRI clones. The average BamHI and EcoRI insert sizes were estimated to be 107.0 kb and 100.8 kb, respectively, and BAC clones lacking inserts were 1.3% and 14.5% in the BamHI and EcoRI libraries, respectively. The two libraries together represent approximately 10.8 haploid cucumber genomes. Hybridization with a C(0)t-1 DNA probe revealed that approximately 36% of BAC clones likely carried repetitive sequence-enriched DNA. The frequencies of BAC clones that carry chloroplast or mitochondrial DNA range from 0.20% to 0.47%. Four sequence-characterized amplified region (SCAR), four simple sequence repeat, and an randomly amplified polymorphic DNA marker linked with yield component quantitative trait loci were used either as probes to hybridize high-density colony filters prepared from both libraries or as primers to screen an ordered array of pooled BAC DNA prepared from the BamHI library. Positive BAC clones were identified in predicted numbers, as screening by polymerase chain reaction amplification effectively overcame the problems associated with an overabundance of positives from hybridization with two SCAR markers. The BAC clones identified herein that are linked to the de (determinate habit) and F (gynoecy) locus will be useful for positional cloning of these economically important genes. These BAC libraries will also facilitate physical mapping of the cucumber genome and comparative genome analyses with other plant species.