Co-location of seed oil content,seed hull content and seed coat color QTL in three different environments in <Emphasis Type="Italic">Brassica napus</Emphasis> L.

Increasing seed oil content is an important breeding goal for Brassica napus L. (B. napus). The identification of quantitative trait loci (QTL) for seed oil content and related traits is important for efficient selection of B. napus cultivars with high seed oil content. To get better knowledge on these traits, a molecular marker linkage map for B. napus was constructed with a recombinant inbred lines (RIL) population. The length of the map was 1,589 cM with 451 markers distributed over 25 linkage groups. QTL for seed oil content, seed hull content and seed coat color in three environments were detected by composite interval mapping (CIM) tests. Eleven QTL accounted for 5.19–13.57% of the variation for seed oil content. Twelve QTL associated with seed hull content were identified with contribution ranging from 5.80 to 22.71% and four QTL for seed coat color accounted for 5.23–15.99% of the variation. It is very interesting to found that co-localization between QTL for the three traits were found on N8. These results indicated the possibility to combine favorable alleles at different QTL to increase seed oil content, as well as to combine information about the relationship between seed oil content and other traits.     

Mapping a diploid wheat abscisic acid 8′-hydroxylase homologue in the seed dormancy QTL region on chromosome 5A<Superscript>m</Superscript>

In Arabidopsis, two genes of abscisic acid (ABA) 8′-hydroxylase (cytochrome P450 (CYP) 707A1 and A2) have been found to play important roles in seed dormancy through the regulation of ABA content in seeds. In order to examine the role of wheat ABA 8′-hydroxylase gene in seed dormancy, a diploid wheat ABA 8′-hydroxylase gene was cloned that showed high similarity to a barley ABA8′-hydroxylase gene (HvABA8′OH-2), and the cloned gene was designated as TmABA8′OH-2. Using recombinant inbred lines derived from a cross between diploid wheat Triticum boeoticum L. (Tb) and Triticum monococcum L. (Tm), TmABA8′OH-2 has been mapped to near the centromeric region of the long arm of chromosome 5A^m, where the major seed dormancy QTL has been previously found. Comparison of the deduced amino acid sequences of TmABA8′OH-2 between Tb and Tm revealed five amino acid residue substitutions. These amino acid residues have distinctly different characteristics, and one of the substitutions occurs in the highly conserved amino acid residues in CYP707A family, indicating that these substitutions may have effects on the enzyme activities. Moreover, hexaploid wheat TmABA8′OH-2 homologue revealed that the level of its expression during seed development peaks at mid-maturation stage. This resembles the expression pattern of the Arabidopsis CYP707A1, which was shown to control seed dormancy. These results imply a possibility that TmABA8′OH-2 might be involved in seed dormancy, and associated with the QTL on chromosome 5A^m.     

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.     

QTLs in barley controlling seedling elongation of deep-sown seeds

In drought areas, in which topsoil moisture is low, barley seeds are generally sown in the subsoil (deep-seeding). In order for the shoots of germinating seeds to emerge from the deep soil cover, the coleoptile and the first internode of the seedlings must elongate as an adaptive response to deep-seeding. Here, we have mapped quantitative trait loci (QTLs) for these adaptive characteristics. Elongation of the coleoptile and first internode was investigated using seeds sown under two soil cover conditions: at a depth of 9 cm beneath a soil mixture; and, at a depth of 12 cm beneath vermiculite. We identified multiple alleles for increased coleoptile and first internode elongation using a doubled haploid population of 150 lines generated from a cross between the barley cultivars Harrington and TR306. Composite interval mapping analyses of the data revealed two moderate and eleven small effect QTLs, with at least one QTL on each chromosome. The QTLs on chromosomes 5H and 7H had moderate effects on coleoptile elongation (18.5–27.6% of PVE: phenotypic variance explained; 2.6–3.2 mm of Add: additive effect) and first internode elongation (PVE: 16.6–19.6%; Add: 3.1–3.2 mm). The small effect QTLs showed PVEs of less than 15% and an Add range of 1.2–3.2 mm for both characters. A marker assisted selection approach, using markers linked to the QTLs for seedling elongation at deep-seeding, may eventually enable development of drought tolerant barley hybrids.     

The use of wild relatives in crop improvement: a survey of developments over the last 20 years

Hypersensitive, race specific genes primarily have been deployed to control powdery mildew (Blumeria graminis (DC) EO Speer f. sp. tritici) in wheat (Triticum aestivum L.); however, recent efforts have shifted to breeding for more durable resistance. Previously, three quantitative trait loci (QTL) for adult plant resistance (APR) to powdery mildew in the winter wheat cultivar Massey were identified in a Becker/Massey (BM) F _2:3 population. Fourteen new simple sequence repeat (SSR) markers were added to the pre-existing BM F _2:3 linkage maps near the QTL for APR on chromosomes 1BL (QPm.vt-1BL), 2AL (QPm.vt-2AL), and 2BL (QPm.vt-2BL). Genetic linkage maps comprised of 17 previously and newly mapped SSRs from the BM population on chromosomes 1BL, 2AL, and 2BL were constructed in a USG 3209/Jaypee (UJ) F _6:7 recombinant inbred line (RIL) confirmation population, wherein the APR resistance of USG 3209 was derived from Massey. Interval mapping analysis of mildew severity data collected in 2002 (F _5:6) and 2003 (F _6:7) field experiments with marker genotypic data obtained in 2003 (F _6:7) confirmed the presence of the three QTL governing APR to powdery mildew in the UJ RILs. The QTL QPm.vt-1BL, QPm.vt-2AL, and QPm.vt-2BL explained 12–13, 59–69, and 22–48% of the phenotypic variance for powdery mildew severity in the UJ confirmation populations, respectively, in two field experiments. The current study verified that the elite wheat cultivar USG 3209 possesses the same QTL for APR as its parent Massey.     

Selection of U and M genome-specific wheat SSR markers using wheat–<Emphasis Type="Italic">Aegilops biuncialis</Emphasis> and wheat–<Emphasis Type="Italic">Ae. geniculata</Emphasis> addition lines

We selected wheat SSR markers specific to the U and M genomes of Aegilops species. A total of 108 wheat SSR markers were successfully tested on Ae. biuncialis (2n = 4x = 28, U^bU^bM^bM^b), on five wheat–Ae. biuncialis addition lines (2M^b, 3M^b, 7M^b, 3U^b and 5U^b) and on a wheat–Ae. geniculata (1U^g, 2U^g, 3U^g, 4U^g, 5U^g, 7U^g, 1M^g, 2M^g, 4M^g, 5M^g, 6M^g and 7M^g) addition series. Among the markers, 86 (79.6%) were amplified in the Ae. biuncialis genome. Compared with wheat, polymorphic bands of various lengths were detected on Ae. biuncialis for 35 (32.4%) of the wheat microsatellite markers. Three of these (8.6%) exhibited specific PCR products on wheat–Ae. biuncialis or wheat–Ae. geniculata addition lines. The primers GWM44 and GDM61 gave specific PCR products on the 2M^b and 3M^b wheat–Ae. biuncialis addition lines, but not on the 2M^g addition line of Ae. geniculata. A specific band was observed on the 7U^g wheat–Ae. geniculata addition line using the BARC184 primer. These three markers specific to the U and M genomes are helpful for the identification of 2M^b, 3M^b and 7U^g chromosome introgressions into wheat.     

Enhancing the identification of genetic loci and transgressive segregants for preharvest sprouting resistance in a durum wheat population

Preharvest sprouting reduces grain quality and lowers grade. Characterization of preharvest sprouting resistance is important in selection in breeding for transgressive segregation and understanding the genetics of the trait for identifying QTL. Methods of measuring dormancy and other factors contributing to preharvest sprouting resistance are varied. The objective of this study was to demonstrate the requirement of multiple methods of measurement over multiple durations of germination to maximize understanding of transgressive segregation and QTL for preharvest sprouting resistance within a segregating durum wheat population grown in multiple environments. Ninety-eight durum wheat (Triticum turgidum L. var. durum) recombinant inbred lines (RIL) from a cross of a minimally dormant line, Sentry, by a moderately dormant line, Kyle, and controls were grown in replicated field tests in 1996, 1997 and 1998 and in a growth chamber trial in 1998. Preharvest sprouting was measured from intact spikes as sprouting index or from hand threshed grain as germination index (GI), germination resistance (GR), and percent germination (PG). The threshed grain measures were evaluated using counts at 7, 14 and 21 days intervals from the start of germination. Correlations performed on the measure type and duration using lines within the RIL population showed some discontinuity across environments, type of measure and duration of measure, with counts at extended intervals for PG producing the lowest correlations. The number of transgressive segregant lines varied with environment, duration and type of measure. Different QTL were identified by different types of measures and duration of counts. GI calculated for 7, 14 and 21 days germination count intervals and GR calculated for 21 days identified a highly significant QTL on chromosome1A (QPhsd.spa.-1A.1). GR calculated for 7 days identified a highly significant QTL on 2A (QPhsd.spa.-2A.1) in two different environments, and GI calculated for 21 days and PG at 7 days identified the same highly significant QTL on chromosome 7B (QPhsd.spa.-7B.1). The results indicated that multiple measures and durations of measure intervals must be applied to results collected across different environments to maximize the identification of QTL and transgressive segregants of the population segregating for preharvest sprouting resistance.     

Mapping chromosomal regions affecting flowering time in a spring wheat RIL population

Flowering time is an important trait for the adaptation of wheat to its target environments. To identify chromosome regions associated with flowering time in wheat, a whole genome scan was conducted with five sets of field trial data on a recombinant inbred lines (RIL) population derived from the cross of spring wheat cultivars ‘Nanda 2419’ and ‘Wangshuibai’. The identified QTLs involved seven chromosomal regions, among which QFlt.nau-1B and QFlt.nau-2B were homoeologous to QFlt.nau-1D and QFlt.nau-2D, respectively. Nanda 2419, the earlier flowering parent, contributed early flowering alleles at five of these QTLs. QFlt.nau-1B and QFlt.nau-7B had the largest effects in all trials and were mapped to the Xwmc59.2–Xbarc80 interval on chromosome 1BS and the Xgwm537–Xgwm333 interval on 7BS. Most of the mapped QTL intervals were not coincident with known vernalization response or photoperiod sensitivity loci and QFlt.nau-1B seems to be an orthologue of EpsA ^m 1. Four pairs of loci showed significant interactions across environments in determining flowering time, all of which involved QFlt.nau-1B. These findings are of significance to wheat breeding programs.     

Stay green trait: variation, inheritance and its association with spot blotch resistance in spring wheat (Triticum aestivum L.)

One thousand four hundred and seven spring wheat germplasm lines belonging to Indian and CIMMYT wheat programs were evaluated for stay green (SG) trait and resistance to spot blotch caused by Bipolaris sorokiniana during three consecutive crop seasons, 1999–2000, 2000–2001 and 2001–2002. Disease severity was recorded at six different growth stages beginning from tillering to late milk stage. SG trait was measured by following two approaches: difference for 0–9 scoring of green coloration (chlorophyll) of flag leaf and spike at the late dough stage (GS 87) and a new approach of leaf area under greenness (LAUG). Germplasm lines showed a wide range (7–89) for LAUG and were grouped into four viz., SG, moderately stay green, moderately non-stay green and non-stay green (NSG). However, very few (2.2%) lines showed high expression of SG trait, i.e., LAUG >60. LAUG appeared to be a better measure of SG trait than a 0–9 scale. Mean spot blotch ratings of SG genotypes were significantly lower than those of NSG genotypes at all growth stages. Two spot blotch resistant genotypes (Chirya 3 and Chirya 7) having strong expressions of SG trait were crossed with NSG, spot blotch susceptible cv. Sonalika. Individually threshed F₂ plants were used to advance the generations. SG trait and spot blotch severity were recorded in the parents and F₁, F₃, F₄, F₅, F₆ and F_6–7 generations under disease-protected and inoculated conditions. SG trait in the F₁ generation was intermediate and showed absence of dominance. Evaluation of progenies (202–207) in the segregating generations revealed that SG trait was under the control of around four additive genes. Lines homozygous for SG trait in F₄, F₅, F₆ and F_6–7 generations showed significantly lower mean area under disease progress curve (AUDPC) for spot blotch than those with NSG expression. A positive correlation (0.73) between SG trait and AUDPC further indicated a positive influence of SG on severity of spot blotch. The study established that variation for SG trait exists in spring wheat; around four additive genes control its inheritance in the crosses studied and there is positive association between SG trait and resistance to spot blotch.     

Genetic mapping within the wheat D genome reveals QTL for germination, seed vigour and longevity, and early seedling growth

Quantitative trait loci (QTL) controlling germination, seed vigour and longevity, and early seedling growth were identified using a set of common wheat lines carrying known D genome introgression segments. Seed germination (capacity, timing, rate and synchronicity) was characterized by a standard germination test, based either on the 1 mm root protrusion (germination sensu stricto) or the development of normal seedlings. To quantify seed vigour, the same traits were measured from batches of seed exposed for 72 h at 43°C and high (ca. 100%) humidity. Seed longevity was evaluated from the relative trait values. Seedling growth was assessed both under non-stressed and under osmotic stress conditions. Twenty QTL were mapped to chromosomes 1D, 2D, 4D, 5D, and 7D. Most of the QTL for germination sensu stricto clustered on chromosome 1DS in the region Xgwm1291–Xgwm337. A region on chromosome 7DS associated with Xgwm1002 harboured loci controlling the development of normal seedlings. Seed vigour-related QTL were present in a region of chromosome 5DL linked to Xgwm960. QTL for seed longevity were coincident with those for germination or seed vigour on chromosomes 1D or 5D. QTL for seedling growth were identified on chromosomes 4D and 5D. A candidate homologues search suggested the putative functions of the genes within the respective regions. These results offer perspectives for the selection of favourable alleles to improve certain vigour traits in wheat, although the negative effects of the same chromosome regions on other traits may limit their practical use.     

Grain dormancy QTL identified in a doubled haploid barley population derived from two non-dormant parents

Grain dormancy provides protection against pre-harvest sprouting (PHS) in cereals. Composite interval mapping and association analyses were performed to identify quantitative trait loci (QTL) contributing grain dormancy in a doubled haploid (DH) barley population (ND24260?×?Flagship) consisting of 321 lines genotyped with DArT markers. Harvest-ripe grain collected from three field experiments was germinated over a 7-day period to determine a weighted germination index for each line. DH lines displaying moderate to high levels of grain dormancy were identified; however, both parental lines were non-dormant and displayed rapid germination within the first two?days of testing. Genetic analysis identified two QTL on chromosome 5H that were expressed consistently in each of the three environments. One QTL (donated by Flagship) was located close to the centromeric region of chromosome 5H (qSDFlag), accounting for up to 15% of the phenotypic variation. A second QTL with a larger effect (from ND24260) was detected on chromosome 5HL (qSDND), accounting for up to 35% of the phenotypic variation. qSDFlag and qSDND displayed an epistatic interaction and DH lines that had the highest levels of grain dormancy carried both genes. We demonstrate that qSDND in the ND24260?×?Flagship DH population is positioned proximal and independent to the well-characterised SD2 region that is associated with both high levels of dormancy and inferior malt quality. This indicates that it should be possible to develop cultivars that combine acceptable malting quality and adequate levels of grain dormancy for protection against PHS by utilizing these alternate QTL.     

Identification of quantitative trait loci and candidate genes controlling the tocopherol synthesis pathway in soybean (Glycine max)

A recombinant inbred line (RIL) population was used to identify quantitative trait loci (QTLs) and their candidate genes controlling the tocopherol (Toc) synthesis pathway. The RIL population was cultivated in field conditions in 3 years. A genetic map constructed using 1624 DNA markers was used for QTL analysis. We identified 22 QTLs for seed tocopherol contents and their ratios, of which two QTL clusters on chromosomes (Chr) 9 and 14 exerted consistent large effects on tocopherol composition across the 3 years. The QTL cluster localized on Chr 9 might correspond to γ-TMT3, which controls the conversion of γ-Toc into α-Toc. The QTL cluster localized on Chr 14 was novel, which might regulate the conversion of MPBQ (a precursor of δ-Toc) into DMPBQ (the precursor of γ-Toc). The effect of the QTL cluster on Chr 14 was validated in a pair of near isogenic lines, and its candidate gene was mined. The identified QTLs and their candidate genes might be used in breeding programmes to improve α-Toc content in soybean seeds.     

Inheritance of (1–3)(1–4)-beta-D-glucan content in barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.)

β-glucan is the soluble dietary fiber component and occurs at its highest in barley. This study aims to evaluate the inheritance of β-glucan content in barley grains and to map quantitative trait loci (QTL) associated with this trait. F₅-derived 107 lines from the cross of the six-rowed waxy hulless barley, ‘Yonezawa Mochi’ and the six rowed non-waxy hulless barley,’ Neulssalbori’ were measured for their agronomic traits and β-glucan level at four different environments. These recombinant lines showed significant genotypic variation (P < 0.01) and normal distribution for β-glucan content with a range of 43.6–62.1 g kg⁻¹ across environments. A significant genotype-by-environment interaction was also found. The broad-sense heritability estimates for β-glucan content ranged from 0.42 to 0.82 across environments. Using one-factor analysis and composite interval mapping, a main effect of QTL associated with β-glucan content was identified in the genomic region near waxy gene (wx) and HVM4 on chromosome 7H. The major QTL at this region explained on average 44.4% of the variation for the mean of β-glucan content across environments with LOD values that ranged from 5.7 in Suwon in 2001 to 13.9 in Suwon in 2003. Two minor QTLs were identified but their significance of association with β-glucan content was inconsistent across environments.     

Identification of QTL underlying the resistance of soybean to pod borer, <Emphasis Type="Italic">Leguminivora glycinivorella</Emphasis> (Mats.) obraztsov,and correlations with plant,pod and seed traits

Soybean (Glycine max L. Merr.) pod borer (Leguminivora glycinivorella (Mats.) Obraztsov) (SPB) results in severe loss in soybean yield and quality in certain regions of the world, especially in Northeastern China, Japan and Russia. The aim here was to evaluate the inheritance of pod borer resistance and to identify quantitative trait loci (QTL) underlying SPB resistance for the acceleration of the control of this pest. Used were the 129 recombinant inbred lines (RILs) of the F_5:6 derived population from ‘Dong Nong 1068’ × ‘Dong Nong 8004’ and 131 SSR markers. Correlations between the percentage of damaged seeds (PDS) by pod borer and plant, pod and seed traits that were potentially related to SPB resistance were analyzed. The results showed highly significant correlations between PDS by pod borer and plant height (PH), maturity date (MA), pod color (PC), pubescence density (PB), 100-seed weight (SW) and protein content existed. Soybeans with dwarf stem, light color of pod coat, small seeds, lower density of pubescence, early maturity and low content of protein seemed to have higher resistance to SPB. The correlated traits had potential to inhibit egg deposition and thereby to decrease the damage by SPB. Three QTL directly associated with the resistance to SPB judged by PDS at harvest were identified. qRspb-1 (Satt541–Satt253) and qRspb-2 (Satt253–Satt314) were both on linkage group (LG) H and qRspb-3 (Satt288–Satt199) on LG G. The three QTL explained 10.96, 9.73 and 11.59% of the phenotypic variation for PDS, respectively. In addition, 12 QTL that underlay 10 of 13 traits potentially related with SPB resistance were found. These QTL detected jointly provide potential for marker assisted selection to improve cultivar resistance to SPB. Guiyun Zhao, Jian Wang, and Yingpeng Han have equal contribution to the paper.     

Genetic analysis of pre-harvest sprouting in a durum wheat cross

Pre-harvest sprouting of durum wheat (Triticum turgidum L. var durum) reduces commercial grade, although the actual effects on processing quality are controversial. Little is known about the genetics of the dormancy component of pre-harvest sprouting resistance in durum. We studied the segregation of dormancy in 98 recombinant inbred lines from a cross of a relatively non-dormant line, CI13102, with a moderately dormant line, Kyle. The lines and parents were grown in field tests over three years, 1996, 1997 and 1998. Spikes were collected at approximately 20% moisture and stored at −23 ∘C. Hand-threshed grain of the lines was germinated, and number of seeds germinated was counted each day. A germination resistance index was calculated to characterize dormancy. Dormancy appeared to be complexly inherited in this cross. Lines were observed that were significantly (P < 0.05) more dormant than the parents. The lines transgressive for dormancy expressed in different combinations of the three environments, indicating an environmental interaction. DNA of lines and parents was tested with simple sequence repeat primers and AFLPs that were used in quantitative trait loci (QTL) analysis of dormancy. Significant QTLs for dormancy were found, with the most notable being on chromosome 1A, where other QTLs for pre-harvest sprouting resistance have been reported in common wheat.     

Using three selected overlapping RILs to fine-map the yield component QTL on Chro.D8 in Upland cotton

Cotton yield improvement is vital to fulfill rising global demands. The identification of major quantitative trait loci (QTL) for yield components was helpful in molecular marker-assisted selection (MAS) to improve cotton yield. We previously identified a densely populated QTL region for fiber qualities and yield components on chromosome D8 (Chro.D8) of Upland cotton from a (7235 × TM-1)RIL. In the present study, to fine-map yield component QTLs, we chose three overlapped recombinant inbred lines (RILs) with different intervals included the yield component QTLs, and backcrossed each line with TM-1 to develop three large sized mapping populations. Phenotypic data for yield components were collected in Nanjing (JES/NAU) and Xinjiang (BES/XJ) in 2006 and 2007. Three simple sequence repeat (SSR) genetic linkage maps on chro.D8 were constructed using 907 individuals in (7TR-133 × TM-1)F₂ (Pop A), 670 in (7TR-132 × TM-1)F₂ (Pop B), and 940 in (7TR-214 × TM-1)F₂ (Pop C). Three stable QTLs for boll size, two for lint percentage and one for boll number per plant,were detected on chro.D8 following analysis of three RIL backcrossed F₂/F_2:3 progeny at JES/NAU and BES/XJ although their cultivation practices differ greatly between these two cotton-growing regions. One QTL for boll number per plant exhibited a phenotypic variance (PV) of 5.6–10.1%, three QTLs for boll size exhibited 15.0–35.5% PV and two lint percentage QTLs exhibited 10.9–19.3% PV. Negative correlation between lint yield and fiber strength was confirmed.     

Analysis of quantitative trait loci underlying the period of reproductive growth stages in soybean (<Emphasis Type="Italic">Glycine max</Emphasis> [L.] Merr.)

Quantitative trait loci (QTLs) underlying reproductive growth stages are important for molecular breeding of soybeans [Glycine max (L.) Merr.]. Most of these QTLs identified so far derived from a single environment, and thus may be influenced by specific environmental conditions. In this study (from 2004 to 2005), analysis of QTLs underlying the period to reach a given reproductive growth stage was performed in three different environments (Harbin, Heilongjiang Province, China). QTL analysis was achieved with a recombination inbred line (RIL) population consisting of 153 lines. The RIL population derived from a cross between an American semi-dwarf cultivar (cv. Charleston) and a Chinese line with a short growth stage (cv. Dongnong 594). The growth stage data of soybean was recorded for each day. QTLs for all eight reproductive growth stages of soybean (R1 to R8) were analyzed by a composite interval mapping method combined with a mixed genetic model. Fifty-four QTLs displayed main effects and 56 QTL pairs showed epistatic effects. Two marker intervals (Satt173–Satt581, Satt402–Satt267), located on the linkage group O and D1a respectively, strongly influenced plant developmental processes during reproductive growth stages. The findings of this study open the possibility to modulate the structure of soybean growth stages by marker-assisted selection and pyramiding QTL analysis. H.-M. Qiu and D.-W. Xin contributed equally to this work.     

Genetic analysis of salt tolerance in a recombinant inbred population of wheat (Triticum aestivum L.)

A population of 114 recombinant inbred lines (RILs), derived from the cross Opata85 × W7984, was used to genetically analyze the response of wheat to salt stress. This analysis resulted in the identification of 47 QTL mapping to all wheat chromosomes except 1B, 1D, 4B, 5D and 7D. Of these QTL, 10 were effective during the germination stage, and 37 at the seedling stage. Many of the traits related to salt tolerance mapped to common chromosome intervals, such as Xglk683–Xcdo460 on chromosome 3A, Xfbb168–Xbcd147 on chromosome 3B, Xcdo1081–Xfbb226 on chromosome 4DL and Xpsr106–Xfbb283 on chromosome 6DL. QTL located in the interval Xcdo1081–Xfbb226 (chromosome 4DL) were effective during the germination stage, whereas those in the interval Xfbb231.1–Xmwg916 (chromosome 6DL) were relevant to the seedling stage. The QTL in the intervals Xglk683–Xcdo460 (chromosome 3AS) and Xfbb168–Xbcd147 (chromosome 3BL) were effective at both the germination and seedling stages.     

QTL mapping for flour and noodle colour components and yellow pigment content in common wheat

Improvement of flour colour is an important breeding objective for various wheat-based end-products. The objectives of this study were to identify quantitative trait loci (QTL) for flour colour components and yellow pigment content (YPC), using 240 recombinant inbred lines (RILs) derived from a cross between the Chinese wheat cultivars PH82-2 and Neixiang 188. Field trials were performed in a Latinized α-lattice design in Anyang and Jiaozuo, Henan Province and Taian, Shandong, in the 2005–2006 and 2006–2007 cropping seasons providing data for six environments. One hundred and eighty-eight polymorphic SSR markers, rye secalin marker Sec1, STS markers YP7A for a phytoene synthase gene (Psy-A1), and four glutenin subunit markers, were used to genotype the population and construct the linkage map for subsequent QTL analysis. Two major QTL were detected for YPC, associated with 1RS (1B.1R translocation) and the Psy-A1 (7A) gene, explaining 31.9% and 33.9% of the phenotypic variances, respectively. 1RS also had large influences on Fa*, Fb*, KJ, NL*and Nb*, and Psy-A1 genes showed large effects on Fa*, Fb*, Kj, Fci, NL*, Na* and Nb*, explaining from 4.5 to 26.1% and 4.3 to 35.9% of the phenotypic variances, respectively. In addition, QTL for flour colour parameters and yellow pigment content were also detected on chromosomes 1A and 4A, accounting for 1.5–4.1% of the phenotypic variance. The genetic effect of the 1B.1R translocation on flour colour parameters was also discussed.     

Identification of quantitative trait loci underlying soybean (Glycine max [L.] Merr.) seed weight including main,epistatic and QTL × environment effects in different regions of Northeast China

Seed weight (SW) is the important soybean (Glycine max [L.] Merr.), yield component and also affected the quality of soybean‐derived foods. The aim of this study was to identify the quantitative trait loci (QTL) underlying SW through 112 recombinant inbred lines (RILs) derived from the cross between “Zhongdou27” (G. max, designated by its bigger seed size, 21.9 g/100 seeds) and “Jiunong 20” (G. max, smaller seed size, 17.5 g/100 seeds). Phenotypic data were collected from this RIL population after it was grown in the sixteen tested environments. A total of eight QTL (QSW1‐1, QSW2‐1, QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1) were identified, and they could explain 4.23%–14.65% of the phenotypic variation. Among these eight QTL, three QTL (QSW1‐1 located on the interval of Sat_159‐Satt603 of chromosome (Chr) 1 (LGD1a), QSW19‐1 located on the interval of Sat_340‐Satt523 of Chr 19 (LGL) and QSW20‐1 located on Sat_418‐Sat_105 of Chr 20 (LGI)) were newly identified and could explain 4.235%–10.08%, 8.45%–13.49% and 8.08%–10.18% of the phenotypic variation, respectively. Six of the eight identified QTL including QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1 exhibited a significant additive (a) effect, while two QTL (QSW2‐1 and QSW19‐1) only displayed significant additive‐by‐environment (ae) effects. A total of four epistatic pairwise QTL for SW were identified in the different environments. These eight QTL and their genetic information obtained here were valuable for molecular marker‐assisted selection and the realization of a reasonable SW breeding programme in soybean.