Analysis of quantitative trait loci associated with leaflet types in two recombinant inbred lines of soybean

Leaf area, length and width affect the photosynthetic capability of a plant and so increasing the photosynthetic rate per unit leaf area may improve seed yield in soybean. In this study, simple sequence repeat (SSR) markers were used to identify the genomic regions significantly associated with the quantitative trait locus (QTL) that controls length, width and the length/width ratio of the terminal and lateral leaflet in two segregating F_2:10 recombinant inbred line (RIL) populations, ‘Keounolkong’ × ‘Shinpaldalkong’ (K/S) and ‘Keounolkong’ × ‘Iksan10’ (K/I). In the K/S population, one QTL was identified for terminal leaflet length (TLL), two for lateral leaflet length (LLL), four for terminal leaflet width (TLW), four for lateral leaflet width (LLW), two for terminal leaflet length/width ratio (TLR) and four for lateral leaflet length/width ratio (LLR), with total phenotypic variations of 7.43, 10.9, 26.57, 23.46, 20.25 and 23.31%, respectively. In the K/I population, two QTLs were identified for TLL, two for LLL, three for TLW, and two for LLW, four for TLR and two for LLR with total phenotypic variations of 29.89, 22.77, 18.5, 12.15, 22.96 and 17.85%, respectively. Only a few QTLs coincided among the leaflet traits and no relationships were observed between the two populations. Many QTLs were associated with leaflet traits but each single QTL made only a minimal contribution. Thus, pyramiding the favourable alleles for leaflet traits in soybean breeding programmes may accelerate vegetative growth and perhaps lead to higher yields by maximizing total photosynthetic performance.     

Dissection of component QTL expression in yield formation in rice

Yield and its components were investigated by using a population of 241 recombinant inbred lines (F₉ RILs) derived from an elite hybrid rice cross of ‘Zhenshan 97’בMinghui 63′. Quantitative trait loci (QTLs) for causal analysing of yield traits were detected at different yield component (YC) influences by conditional and unconditional QTL mapping methods. The number of QTLs significantly affecting yield was different at component‐special influence. Some QTLs controlling yield identified in one component influence were undetectable at the others. More QTLs for yield could be detected at different YC influences. It is possible to reveal that causal gene expression for yield could be different at different YC influences. Mapping QTLs for component effects of yield could help us in understanding the nature of cause‐effect traits for the formation of grain yield.     

Interrelationships among height,lodging and yield in determinate and indeterminate soybeans

Summary Seventy-three determinate and 93 indeterminate random F₉ lines from a cross between determinate and indeterminate soybean [Glycine max (L.) Merr.] parents were evaluated for seed yield, mature plant height, and lodging. Regression analyses indicated that among the determinate lines, seed yield increased by 350 kg/ha and lodging score increased by 0.008 for every 10 cm increase in plant height. Among indeterminate lines seed yield increased by 112 kg/ha and lodging score by 0.3 for every 10 cm increase in plant height. The highest yielding indeterminate lines were tall and very susceptible to lodging. The tall determinate lines had the best combination of high seed yield and excellent lodging resistance.Cooperative Investigations of the Science and Education Administration, U.S. Department of Agriculture and the Purdue University Agricultural Experiment Station.     

QTL analysis of kernel shape and weight using recombinant inbred lines in wheat

Quantitative trait locus (QTL) analysis of kernel shape and weight in common wheat was conducted using a set of 131 recombinant inbred lines (RIL) derived from ‘Chuan 35050’ × ‘Shannong 483’. The RIL and their two parental genotypes were evaluated for kernel length (KL), kernel width (KW), thousand-kernel weight (TKW), and test weight (TW) in four different environments. Twenty QTL were located on 12 chromosomes, 1A, 1B, 1D, 2A, 2B, 3B, 4A, 4B, 5D, 6A, 6B, and 7B, with single QTL in different environments explaining 5.9–26.4% of the phenotypic variation. Six, three, four, and seven QTL were detected for KL, KW, TKW, and TW, respectively. The additive effects for 17 QTL were positive with Chuan 35050 increasing the QTL effects, whereas the remaining three QTL were negative with Shannong 483 increasing the effects. Eight QTL (40%) were detected in two or more environments. Two QTL clusters relating to KW, TKW, and TW were located on chromosomes 2A and 5D, and the co-located QTL on chromosome 6A involved a QTL for KW found in two environments and a QTL for TKW detected in four environments.     

Parent genome contribution and its relationship with grain yield in backcross-derived lines of soybean (Glycine max)

Introgression of yellow mosaic disease (YMD) resistance and effect of recurrent parent genome (RPG) on grain yield was studied in 84 soybean genotypes from four populations namely, F_2:7, BC₁F₆, BC₂F₅ and BC₃F₄ derived from cross JS335 x SL525. It was observed that in F_2:7, BC₁F₆, BC₂F₅ and BC₃F₄ derived lines, RPG contribution was 42.5%, 54.9%, 66.4% and 77.6%, respectively, which is significantly less than expected values. Linkage drag from donor parent with YMD resistance gene may be a possible reason for such deviations. Average grain yield per plant in F_2:7, BC₁F₆, BC₂F₅ and BC₃F₄ generations was observed as 13.0, 14.3, 14.9 and 16.1 g, respectively. It was observed that genotypes with more than 80% RPG observed to have both YMD resistance and good yield potential. Graphical genotyping (GGT) analysis revealed that maximum RPG was recovered in chromosomes 8 and 10 and maximum introgression occurred in chromosomes 6 and 19. Our results demonstrated that RPG was positively associated with yield as evident from yield increase with increase in RPG.     

Path-coefficient analysis of some yield components of sunflower (Helianthus annuus L.), I

Summary Interactions of seven bio-morphological characteristics of sunflower (head diameter, number of flowers per head, number of seeds per head, 1,000-seed weight, volume weight, kernel content in seed, oil content) and their correlations with seed yield per plant were examined. The path-coefficient analysis provided information about direct and indirect effects of the examined characteristics on seed yield per plant. The correlation coefficients were positive and highly significant. The highest direct positive effect on seed yield per plant was exhibited by the weight of 1,000 seeds. Head diameter, volume weight and kernel content had a direct negative effect on seed yield per plant.     

Comparative genome mapping of Sorghum bicolor (L.) Moench using an RFLP map constructed in a population of recombinant inbred lines

A restriction fragment length polymorphism (RFLP) linkage map of Sorghum bicolor (L.) Moench was constructed in a population of 137 F_6-8 recombinant inbred lines using sorghum, maize, oat, barley and rice DNA clones. The map consists of 10 linkage groups (LGs) and 323 markers, 247 of which (76.5%) were ordered at a LOD score ≥ 3.0. The LGs comprise from 61 (LG A) to 13 markers (J), which range in length from 205 (A) to 55 cM (J) and have a combined total length of 1347 cM. Highly significant distorted segregation was detected at all of the 38 loci in a 103-cM segment of LG A, the allelic ratios in the segment ranging from approximately 3:1 (one end) to 19:1 (middle) to 2:1 (other end). Duplicated loci located in different LGs have been mapped with 55 of the 295 DNA probes used in the study (18.6%). The distribution of these loci does not provide support for the hypothesis that Sorghum bicolor (L.) Moench is of tetraploid origin. Comparison of the map with RFLP maps of maize, rice, and oat produced evidence for sorghum-maize LG rearrangements and homoeologies not reported previously, including evidence that: (1) a segment of maize 5L and a segment of 5S may be homoeologous to sorghum LGA; (2) maize LGs 4 and 6 are partly homoeologous to sorghum LGE; (3) the short arm of maize LG 2 is partly homoeologous to sorghum LGF; (4) maize LG 4 may be partly homoeologous to sorghum LG G; (5) maize LG 5 and sorghum LG G contain a larger amount of homoeologous genetic material than previously indicated; and (6) a short segment of maize LG 1 may be homoeologous to a short segment of sorghum LG I.     

陆地棉重组自交系群体纤维品质及产量性状遗传变异分析

以陆地棉优质品系0-153和大面积推广的双价转基因抗虫棉品系sGK9708为亲本构建了含有196个F6:8家系的重组自交系群体。在4个环境中,纤维长度、纤维强度、麦克隆值、伸长率、整齐度指数、单株结铃数、铃重、衣分、子指、单株子棉产量及单株皮棉产量等性状均呈正态分布,且存在双向超亲分离。多环境下变异分析表明,各性状家系间及环境间存在极显著差异。除纤维伸长率外,其余各纤维品质及产量性状都具有较高的遗传力,在0.75以上。共有6个家系在纤维长度、细度和强度性状上均超过高亲,可作为优质纤维种质。相关分析显示,有些家系可能打破了纤维品质和产量性状间的负相关。通过聚类分析得出,该群体各系分在了不同的组,表明存在着一定的遗传差异。该群体是进行优异纤维品质相关基础研究的良好材料。     

Genetic analysis and map-based delimitation of a major locus qSS3 for seed size in soybean

Seed size is a major determinant of grain yield in soybean, however their genetic basis remains largely unknown. In order to delimit map-based position of a major locus qSS3 , we evaluated three mapping populations, including RILs, NILs and a sub-F₂ in three environments for six seed size-related traits. For these traits, the kurtosis and skewness ranged between 0.0 and 1.16, while h²_b ranged from 0.75 to 0.96, indicating that this RIL population is suitable for QTL analysis. QTL analysis identified 12 loci which consist of 30 significant QTLs with PVE% and LOD values of 6.6%–26.2% and 2.50–5.61, respectively. Among them, qSS3 was a major and stable locus explaining 7.3%–26.2% of the variation in 5 of the 6 traits, with the respective LOD values falling in the range of 2.72–5.61. Additionally, qSS3 effects were confirmed in NILs and delimited to an interval of ~1,126 kb containing 123 annotated genes. Overall, this study may assist efforts aiming to improve soybean seed traits by identifying valuable genetic resources which can be used in future MAS breeding programmes.     

Estimates of relative contribution of biomass, harvest index and yield components to soybean yield improvements in China

A method was developed to estimate the relative contribution of increased biomass, harvest index and yield components to seed yield gain of soybean. Data from four field experiments conducted in three soybean production regions in China were used to measure the role of different traits (such as harvest index) in seed yield improvement by applying this method. The results indicated that harvest index was a larger contributor to the progress of soybean yield improvements than biomass in China. However, the estimates of improvements of yield components suggested that there could be several strategies for obtaining high yield. High yielding would be achieved by improving all of the three yield components (pods per plant, seeds per pod and seed weight) simultaneously, or significantly improving one or two of the three components.     

Genetic association of yield with its component traits in a recombinant inbred line population of cotton

Lint yield of upland cotton (Gossypium hirsutum L.) is determined by its component traits, boll number, boll weight, and lint percentage. Selecting high yielding lines is based on the ability to manipulate component traits. In this study, 188 recombinant inbred lines and two parental lines were grown in 1999 and 2000 at Mississippi State University. Lint yield and its three component traits were measured and analyzed by an extended conditional mixed linear model approach. Boll number unit-area^–1 made the largest contribution to genotypic and genotype × environment (G × E) variations for lint yield. Both boll number and lint percentage, and boll number and boll weight jointly accounted for more than 70% of the genotypic and G × E variations in lint yield. Ninety-nine percent of the genetic and phenotypic variation in lint yield could be explained by the three component traits, indicating that lint yield was mainly dependent on its three component traits. Small phenotypic variation in lint yield could be accounted for by effects of genotype, G × E interactions of boll number or boll number combined with other component trait(s) (Table 5). For boll number unit-area^–1 a wider distribution of genotypic contribution effects was detected than for lint percentage and boll weight in this study. Boll number and boll weight interacted to affect lint yield, indicating that balanced selection for boll weight and boll number is needed in high-yielding line development. Comparative results with other approaches were also discussed in this study.The U.S. Governments right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged     

Seed yield and its components in smooth bromegrass (Bromus inermis Leyss.) cultivars

Summary Seed yield performance and effect on seed yield of morphological traits such as seeds/panicle, seed weight, seeds/branch, branches/2nd node, branches/panicle, fertile tillers/plant and panicle length were evaluated in 13 cultivars of smooth bromegrass in a spaced-plant nursery. Wide variation was observed between and within cultivars for seed yield and traits. Highly significant correlation coefficients were found among traits and seed yield. Path analysis showed that specifically seeds/panicle and seed weight had strong direct effect on seed yield. It was concluded that seeds/panicle and seed weight were primary selection criteria for seed yield in smooth bromegrass.     

Estimates of variance components and repeatability for total forage yield in rye: implications for breeding

Cereal rye (Secale cereale L.) is an important forage crop in the USA for stocker cattle (Bos sp.) production, thus making forage yield an important breeding objective for the crop. However, little information is known about the repeatability for forage yield in this crop. The objectives of this research were to: (i) estimate variance components for forage yield from long‐term variety trials, (ii) estimate the repeatability for forage yield and (iii) relate this to breeding strategies for increased forage yield in rye. Trials were conducted over 14 years where 97 USA open‐pollinated varieties (OPVs) were evaluated. Repeatability ranged from 0.57 to 0.86 when the data were analysed by year for the 3 years with significant genotype main effects. Possible explanations for the lack of significant genotype main effects are discussed. Practical implications of these findings indicate that the development of improved cultivars with greater forage yield will require improved methods of selection based on family performance rather than the current methods based primarily on single plant visual selection.     

Influence of environmental productivity levels and yield stability on selection strategies in soybean

Summary Yield data were collected for soybean (Glycine max (L.) Merr.) lines in maturity groups III and IV in 14 environments from 1985 to 1989. The lines in each maturity group were subdivided into three different groups based on the mean yield over all environments, and the genotype × environment interactions were studied for each group. Yield stability of the lines was determined. Effectiveness of selection based on different types of environments was examined.Productivity level of the environment did not influence the relative ranking of the lines. Significant rank correlations occurred between mean yields in most environments and the overall mean yield, but few similarities occurred in the line rankings among individual environments. High-yielding lines contributed a significantly smaller proportion to the genotype × environment interaction than medium- and low-yielding lines.A small proportion of the lines were below or above average stability. Significant correlations occurred among stability, overall mean yield, and mean yield in high- and low-yielding environments. However, few significant correlations occurred between individual environment yields and stability in high- or low-yielding environments. Maturity groups differed in yield and stability relationships. Stability in high- and low-yielding environments did not adequately predict stability for each other.Contribution No. 93-445-J from the Kansas Agricultural Experient Station     

Detection of QTLs for bread‐making quality in wheat using a recombinant inbred line population

Whereas gluten fraction accounts for 30–60% of the variation in wheat bread‐making quality, there remains substantial variation determined by non‐gluten factors. The objective of this study was to detect new loci for wheat quality. The genetics of sodium dodecyl sulphate‐sedimentation volume (Ssd), grain hardness (GH), grain protein content, wet gluten content (WGC) and water absorption (Abs) in a set of 198 recombinant inbred lines derived from two commercial varieties was studied by quantitative trait loci (QTL) analysis. A genetic map based on 255 marker loci, consisting of 250 simple sequence repeat markers and five glutenin loci, Glu‐A1, Glu‐B1, Glu‐D1, Glu‐B3 and Glu‐D3, was constructed. A total of 73 QTLs were detected for all traits. A major QTL for GH was detected on chromosome 1B and its relative contribution to phenotypic variation was 27.7%. A major QTL for Abs on chromosome 5D explained more than 30% of the phenotypic variation. Variations in Ssd were explained by four kinds of genes. Some QTLs for correlated traits mapped to the same regions forming QTL clusters or indicated pleiotropic effects.     

Identification and validation of quantitative trait loci associated with seed yield in soybean

In soybean [Glycine max (L.) Merrill], the genetic analysis of seed yield is important to aid in the breeding of high-yielding cultivars. Seed yield is a complex trait, and the number of quantitative trait loci (QTL) involved in seed yield is high. The aims of this study were to identify QTL associated with seed yield and validate their effects on seed yield using near-isogenic lines. The QTL analysis was conducted using a recombinant inbred line population derived from a cross between Japanese cultivars ‘Toyoharuka’ and ‘Toyomusume’, and eight seed yield-associated QTL were identified. There were significant positive correlations between seed yield and the number of favorable alleles at QTL associated with seed yield in the recombinant inbred lines for three years. The effects of qSY8-1, a QTL promoting greater seed yield, was validated in the Toyoharuka background. In a two-year yield trial, the 100-seed weight and seed yield of Toyoharuka-NIL, the near-isogenic line having the Toyomusume allele at qSY8-1, were significantly greater than those of Toyoharuka (106% and 107%, respectively) without any change for days to flowering and maturity. Our results suggest that qSY8-1 was not associated with maturity genes, and contributed to the 100-seed weight.     

Effects of high oleic acid soybean on seed yield,protein and oil contents,and seed germination revealed by near‐isogeneic lines

Typical soybean oil is composed of palmitic, stearic, oleic, linoleic and linolenic acids. High oleic acid content in soybean seed is a key compositional trait that improves oxidative stability and increases oil functionality and shelf life. Using a marker‐assisted selection method, near‐isogenic lines (NILs) of G00‐3213 for the high oleic trait were developed and yield tested. These NILs have various combinations of FAD2‐1A and FAD2‐1B alleles that were derived from the same backcrossing populations. The results indicated that G00‐3213 NILs with both homozygous mutant FAD2‐1A and FAD2‐1B alleles produced an average of 788 g/kg oleic acid content. The results also demonstrated that possessing these mutant alleles did not cause a yield reduction. Furthermore, seed germination tests across 12 temperatures (12.8–32.0°C) showed that modified seed composition for oleic acid in general did not have a major impact on seed germination. However, there was a possible reduction in seed germination vigour when high oleic seeds are planted in cold soil. The mutant FAD2‐1A and FAD2‐1B alleles did not hinder either seed or plant development.     

Relationships between genetic distance measured by RAPD-PCR and heterosis in inbred lines of white clover (Trifolium repens L.)

The RAPD-PCR technique has been used to generate DNA amplification profiles from a set of advanced generation inbred lines of white clover ( Trifolium repens L.). The genetic distances between lines have been estimated and have been compared with the extent of positive heterosis for dry matter yield in hybrid crosses. The analysis clearly separated the four major groups (H, J, R and S), with little within group variation. Heterosis, previously shown to be positively correlated with the extent of phenotypic variation between parental lines, was greatest between lines from groups showing the least genetic distance. The lack of correlation between heterosis and genetic divergence is discussed in the context of results from other systems. Additionally, the data allow a comparison of the extent of phenotypic variation for a trait under selective pressure with the degree of variation at the DNA level detected with the RAPD technique. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of d2 dwarfing gene on grain yield and yield components in pearl millet near-isogenic lines

Summary A d₂ dwarfing gene in pearl millet [Pennisetum glaucum (L.) R. Br.] is currently being extensively used for the development of hybrid parents. Its effect on grain yield and yield components is poorly understood. Twelve pairs of tall and dwarf near-isogenic lines developed in the diverse genetic background of three composites were evaluated for grain yield and yield components for 2 years at two locations in southern India. The d₂ gene or the genes linked to it, on an average, reduced plant height by 42%, grain yield by 14%, and head girth by 8% but increased head length and number of tillers per plant by about 5–6%. Large variations were observed among pairs (genetic background) for the difference between tall and dwarf near-isogenic lines for all of the above yield components resulting in no significant difference in five pairs and 17–35% less yield in dwarfs as compared to their tall counterparts in six pairs. Days to 50% flowering and seed weight were least affected by the d₂ gene with the average difference between tall and dwarf groups of near-isogenic lines being of the order of 1–2%. These results indicate that the advantageous effects of d₂ dwarfing gene can be effectively exploited by manipulating the genetic background. The difference between the average grain yields of tall and dwarf groups of near-isogenic lines showed considerable variation across environments with the dwarfs yielding as much as tall group in one environment and up to 30% less than the tall group in the other, thus, indicating that the d₂ gene effect may be substantially modified by the environments.Submitted as JA No. 979 by the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT).