Phenotyping of isogenic chlorophyll-less bread and durum wheat mutant lines in relation to photoprotection and photosynthetic capacity

Photosynthesis Research - In our experiments, we examined high light responses and photosynthetic capacity of chlorophyll-less isogenic mutant lines of hexaploid bread wheat (Triticum aestivum L.)...     

Genetic analysis of water-extractable arabinoxylans in bread wheat endosperm

 Two mapping populations were used for the analysis of the water-extractable arabinoxylans. One originated from a cross between the hexaploid cultivars ‘Courtot’ and ‘Chinese Spring’ and the other from a cross between an amphiploid (Synthetic) and cv ‘Opata’. Arabinose (Ara), and xylose (Xyl) contents were quantified for the 91 and 76 lines obtained from the two crosses, respectively. Relative viscosity (η_rel) of the wheat flour aqueous extract was evaluated by capillary viscometry. Both crosses gave similar correlation coefficients between sugar contents and relative viscosity. There were strong positive relationships between arabinose, xylose and arabinoxylan contents. The relative viscosity was strongly and positively related to the arabinoxylan content and strongly and negatively related to the Ara/Xyl ratio (arabinose content to xylose content). For one of the two crosses two measurements of relative viscosity were generated from 2 years of consecutive harvesting. As a strong correlation was observed between these two measurements, an important genotypic effect can be deduced for the relative viscosity of water-extractable arabinoxylans. QTL (quantitative trait locus) research did not reveal any chromosomal segments that were strongly implicated in variations in sugar content. However, a QTL was found for relative viscosity values and the Ara/Xyl ratio on the long arm of the 1B chromosome for the two crosses considered. This QTL explained 32–37% of the variations in relative viscosity and 35–42% of the variations in the Ara/Xyl ratio. Genes located at this QTL controlled relative viscosity through modifying the Ara/Xyl ratio. Variations in the Ara/Xyl ratio were supposedly related to differences in the molecular structure of water-extractable arabinoxylans. Minor QTLs were also obtained for relative viscosity and Ara/Xyl ratio, but the chromosomes concerned were different for the two populations evaluated. Received: 5 January 1998 / Accepted: 15 May 1998     

Genetic analysis of kernel hardness in bread wheat using PCR-based markers

In wheat, kernel hardness is a complex genetic trait involving various directly and indirectly contributing components such as kernel hardness per se, protein content, hectolitre weight and 1,000-kernel weight. In an attempt to identify DNA markers associated with this trait, 100 recombinant inbred lines (RILs) derived from a cross between a hard grain land-race, NP4, and a soft grain variety, HB 208, were screened with 100 ISSR and 360 RAPD primers. Eighteen markers were assigned to seven linkage groups covering 223.6 cM whereas 11 markers remained unlinked. A multiple-marker model explained the percentage of phenotypic variation for kernel hardness as 20.6%, whereas that for protein content, hectolitre weight and 1,000-kernel weight was 18.8%, 13.5% and 12.1%, respectively. Our results indicate that phenotypic expression of kernel hardness is controlled by many QTLs and is interdependent on various related traits. Received: 25 July 2000 / Accepted: 24 November 2000     

Genetic analysis of durable resistance to yellow rust in bread wheat

Yellow rust, caused by Puccinia striiformis, is one of the most damaging diseases affecting bread wheat in temperate regions. Although resistance to yellow rust is frequently overcome by new virulent races, a durable form of resistance in the French bread wheat Camp Rémy (CR) has remained effective since its introduction in 1980. We used 217 F₇ recombinant inbred lines (RILs) derived from the cross between CR and the susceptible cultivar Récital to identify and map quantitative trait loci (QTLs) involved in durable yellow rust resistance. Six significant QTLs that were stable over a 4-year period were detected. Two QTLs, denoted QYr.inra-2DS and QYr.inra-5BL.2, were located on the short arm of chromosome 2D and the long arm of chromosome 5B, respectively. Each explained on average 25–35% of the observed phenotypic variation and were probably inherited from Cappelle Desprez, a parent of CR that confers durable adult plant resistance to yellow rust. QYr.inra-2DS probably corresponds to the Yr16 gene. The most consistent QTL, designated QYr.inra-2BL, was located on the centromeric region of chromosome 2B and explained 61% of the phenotypic variation in 2003. This QTL was responsible for seedling-stage resistance and may correspond to a cluster of genes, including Yr7. The remaining QTLs were mapped to the short arm of chromosome 2B (R²=22–70%) and to the long arm of chromosomes 2A (R²=0.20–0.40) and 5B (R²=0.18–0.26). This specific combination of seedling and adult plant resistance genes found in CR and CD may constitute the key to their durable resistance against yellow rust.     

Genetic analysis of durable leaf rust resistance in winter wheat

Quantitative resistance that delays the epidemic development of leaf rust in wheat is an important source for durable resistance breeding. The Swiss winter wheat variety ’Forno’ shows a high level of quantitative resistance against leaf rust. This resistance has been effective for more than 10 years and can therefore be considered to be durable. In order to map quantitative trait loci (QTL) for durable leaf rust resistance we analysed 204 F₅ recombinant inbred lines (RILs) of the cross between the winter wheat ’Forno’ and the winter spelt ’Oberkulmer’ for their level of leaf rust resistance (LR) and leaf tip necrosis (LTN) in four different environments. Both traits showed a continuous distribution and were significantly correlated (r=−0.5). Across environments we detected 8 QTL for leaf rust resistance (6 inherited from ’Forno’) and 10 QTL for the quantitative expression of LTN (6 inherited from ’Forno’). Of the 6 QTL responsible for the durable leaf rust resistance of ’Forno’, 1 major QTL coincided with a thaumatin locus on 7BL explaining 35% of the phenotypic variance. Four QTL for LR coincided with QTL for LTN. At these loci the alleles of ’Forno’ increased the level of resistance as well as the extent of LTN, indicating pleiotropy. Received: 1 July 1999 / Accepted: 30 July 1999     

Extraction of quantitative characteristics describing wheat leaf pubescence with a novel image-processing technique

Leaf pubescence (hairiness) in wheat plays an important biological role in adaptation to the environment. However, this trait has always been methodologically difficult to phenotype. An important step forward has been taken with the use of computer technologies. Computer analysis of a photomicrograph of a transverse fold line of a leaf is proposed for quantitative evaluation of wheat leaf pubescence. The image-processing algorithm is implemented in the LHDetect2 software program accessible as a Web service at http://wheatdb.org/lhdetect2. The results demonstrate that the proposed method is rapid, adequately assesses leaf pubescence density and the length distribution of trichomes and the data obtained using this method are significantly correlated with the density of trichomes on the leaf surface. Thus, the proposed method is efficient for high-throughput analysis of leaf pubescence morphology in cereal genetic collections and mapping populations.     

Genetic characterization of storage proteins in a set of F1-derived haploid lines in bread wheat

Wheat storage proteins were evaluated by SDS-PAGE in a population of 206 doubled haploid (DH) lines, produced from a cross between bread wheat cvs Chinese Spring (CS) and Courtot (CT). The analysis of gliadins and high- and low-molecular-weight glutenins gave rise to 11 protein markers between parental varieties. Among these, one each was encoded at the Glu-A1, Gli-A1, Gli-A2, Gli-A5, Glu-B3, Gli-B1 and Gli-D1 loci and four were encoded at the Glu-D3 locus. Only the Gli-A2 marker showed a distorted segregation. A distance of 1.94 cM was evaluated between the Gli-A1 locus and the recently found Gli-A5 locus. Among the DH lines, only nine exhibited an unexpected pattern. The chromosome allocation was determined for almost all the LMW-GS and gliadin bands of CS using nullitetrasomic and ditelosomic lines. Two C LMW-GS were found to be coded by 6DS. Similarly, substitution lines into CT allowed the allelic determination of numerous LMW-GS and gliadin bands. A correspondence between gliadin markers separated in SDS-PAGE and in A-PAGE revealed that the common allele Gli-Aa between CS and CT determined in A-PAGE was able to be separated into two alleles when SDS-PAGE was used.     

Molecular-genetic analysis of the breeding bread wheat lines with starch of amylopectin type

PCR-analysis with primers to Wx-loci of T. aestivum L. genome lets us run the controlled selection of genotypes with null-alleles of Wx-genes while creating bread wheat lines with amylopectin type of starch. Microsatellite analysis of selected individual plants which were the carries of three null-alleles of Wx-genes (Wx-A1b, Wx-B1b, Wx-D1b) and the cluster analysis in the complex allowed us to pick out four genotypes, which were very close related genetically to the parent form variety Kuyalnik.     

Genetic dissection of grain yield in bread wheat. I. QTL analysis

Grain yield forms one of the key economic drivers behind a successful wheat (Triticum aestivum L.) cropping enterprise and is consequently a major target for wheat breeding programmes. However, due to its complex nature, little is known regarding the genetic control of grain yield. A doubled-haploid population, comprising 182 individuals, produced from a cross between two cultivars ‘Trident’ and ‘Molineux’, was used to construct a linkage map based largely on microsatellite molecular makers. ‘Trident’ represents a lineage of wheat varieties from southern Australia that has achieved consistently high relative grain yield across a range of environments. In comparison, ‘Molineux’ would be rated as a variety with low to moderate grain yield. The doubled-haploid population was grown from 2002 to 2005 in replicated field experiments at a range of environments across the southern Australian wheat belt. In total, grain yield data were recorded for the population at 18 site-year combinations. Grain yield components were also measured at three of these environments. Many loci previously found to be involved in the control of plant height, rust resistance and ear-emergence were found to influence grain yield and grain yield components in this population. An additional nine QTL, apparently unrelated to these traits, were also associated with grain yield. A QTL associated with grain yield on chromosome 1B, with no significant relationship with plant height, ear-emergence or rust resistance, was detected (LOD ≥2) at eight of the 18 environments. The mean yield, across 18 environments, of individuals carrying the ‘Molineux’ allele at the 1B locus was 4.8% higher than the mean grain yield of those lines carrying the ‘Trident’ allele at this locus. Another QTL identified on chromosome 4D was also associated with overall gain yield at six of the 18 environments. Of the nine grain yield QTL not shown to be associated with plant height, phenology or rust resistance, two were located near QTL associated with grain yield components. A third QTL, associated with grain yield components at each of the environments used for testing, was located on chromosome 7D. However, this QTL was not associated with grain yield at any of the environments. The implications of these findings on marker-assisted selection for grain yield are discussed.     

Genetic analysis of durable resistance against leaf rust in durum wheat

The Italian durum wheat cultivar Creso possesses a high level of durable resistance to leaf rust based on both hypersensitive and non-hypersensitive components. In order to investigate the genetic basis of this resistance, a segregating population composed of 123 recombinant inbred lines (RILs) derived from the cross Creso × Pedroso, was evaluated for disease severity in adult plants under field conditions. Furthermore, the resistance of parents and RILs was evaluated by assessing macroscopically the latency period and microscopically the number and type of pathogen colonies formed following artificial inoculation with a specific isolate. This experiment was performed at controlled conditions at two developmental stages. Besides some minor QTLs, one major QTL explaining both reduction of disease severity in the field and increased latency period was found on the long arm of chromosome 7B, and closely associated PCR-based and DArT markers were identified. Daniela Marone and Ana I. Del Olmo contributed equally to the work.     

Analysis of flavonoids in pubescence of soybean near-isogenic lines for pubescence color loci

T and Td loci control pubescence color of soybean with epistatic effects (TT TdTd, tawny; TT tdtd, light tawny or near-gray; tt TdTd or tt tdtd, gray). The objective of this study was to investigate the nature of flavonoids in the pubescence of near-isogenic lines (NILs) for these loci. Flavonoids were extracted with methanol from pubescence of cultivar Clark with tawny pubescence (TT TdTd) and its NILs; from Clark-t with gray pubescence (tt TdTd) and Clark-td with near-gray pubescence (TT tdtd); and from a pair of NILs, To7B with tawny (TT TdTd) and To7G with gray pubescence (tt TdTd). Primary flavonoids were flavone aglycones. Luteolin and apigenin were predominant in NILs with tawny and gray pubescence, respectively. Small amount of 7-O-glucosides of the 2 flavones were also detected. Alleles at T locus were associated with 3'-hydroxylation in the B-ring of the flavones. The primary flavonoids in Clark-td were luteolin similar to Clark, but its amount was halved. High performance liquid chromatography peaks probably corresponding to isoflavonoids were found only in Clark-td in 2003. However, the peaks were not observed in 2005. The above results suggest that Td may encode a structural or a regulatory gene controlling flavone biosynthesis. Pigments remained visible in pubescence after methanol extraction, suggesting that a major part of the pigments was polymerized. Surface rinsing experiments revealed that flavone aglycones exist outside the surface of cells.     

Genetic analysis of carbon isotope discrimination and agronomic characters in a bread wheat cross

Carbon isotope discrimination () has been suggested as a selection criterion to improve transpiration efficiency (W) in bread wheat (Triticum aestivum L.). Cultivars Chinese Spring with low A (high W) and Yecora Rojo with high (low W) were crossed to develop F₁, F₂, BC₁, and BC₂ populations for genetic analysis of and other agronomic characters under well-watered (wet) and water-stressed (dry) field conditions. Significant variation was observed among the generations for only under the wet environment. Generation x irrigation interactions were not significant for . Generation means analysis indicated that additive gene action is of primary importance in the expression of under nonstress conditions. Dominance gene action was also detected for , and the direction of dominance was toward higher values of . The broad-sense and the narrow-sense heritabilities for were 61 % and 57% under the wet conditions, but were 48% and 12% under the draughted conditions, respectively. The narrow-sense heritabilities for grain yield, above-ground dry matter, and harvest index were 36%, 39%, and 60% under the wet conditions and 21%, 44%, and 20% under dry conditions, respectively. The significant additive genetic variation and moderate estimate of the narrow-sense heritability observed for indicated that selection under wet environments should be effective in changing in spring bread wheat.     

Genetic analysis of grain protein-content,grain yield and thousand-kernel weight in bread wheat

Grain yield and grain protein content are two very important traits in bread wheat. They are controlled by genetic factors, but environmental conditions considerably affect their expression. The aim of this study was to determine the genetic basis of these two traits by analysis of a segregating population of 194 F(7) recombinant inbred lines derived from a cross between two wheat varieties, grown at six locations in France in 1999. A genetic map of 254 loci was constructed, covering about 75% of the bread wheat genome. QTLs were detected for grain protein-content (GPC), yield and thousand-kernel weight (TKW). 'Stable' QTLs (i.e. detected in at least four of the six locations) were identified for grain protein-content on chromosomes 2A, 3A, 4D and 7D, each explaining about 10% of the phenotypic variation of GPC. For yield, only one important QTL was found on chromosome 7D, explaining up to 15.7% of the phenotypic variation. For TKW, three QTLs were detected on chromosomes 2B, 5B and 7A for all environments. No negative relationships between QTLs for yield and GPC were observed. Factorial Regression on GxE interaction allowed determination of some genetic regions involved in the differential reaction of genotypes to specific climatic factors, such as mean temperature and the number of days with a maximum temperature above 25 degrees C during grain filling.     

Composition and functional analysis of low-molecular-weight glutenin alleles with Aroona near-isogenic lines of bread wheat

Background

The polyphenolic products of the phenylpropanoid pathway, including proanthocyanidins, anthocyanins and flavonols, possess antioxidant properties that may provide health benefits. To investigate the genetic architecture of control of their biosynthesis in apple fruit, various polyphenolic compounds were quantified in progeny from a 'Royal Gala' × 'Braeburn' apple population segregating for antioxidant content, using ultra high performance liquid chromatography of extracts derived from fruit cortex and skin.

Results

Construction of genetic maps for 'Royal Gala' and 'Braeburn' enabled detection of 79 quantitative trait loci (QTL) for content of 17 fruit polyphenolic compounds. Seven QTL clusters were stable across two years of harvest and included QTLs for content of flavanols, flavonols, anthocyanins and hydroxycinnamic acids. Alignment of the parental genetic maps with the apple whole genome sequence in silico enabled screening for co-segregation with the QTLs of a range of candidate genes coding for enzymes in the polyphenolic biosynthetic pathway. This co-location was confirmed by genetic mapping of markers derived from the gene sequences. Leucoanthocyanidin reductase (LAR1) co-located with a QTL cluster for the fruit flavanols catechin, epicatechin, procyanidin dimer and five unknown procyanidin oligomers identified near the top of linkage group (LG) 16, while hydroxy cinnamate/quinate transferase (HCT/HQT) co-located with a QTL for chlorogenic acid concentration mapping near the bottom of LG 17.

Conclusion

We conclude that LAR1 and HCT/HQT are likely to influence the concentration of these compounds in apple fruit and provide useful allele-specific markers for marker assisted selection of trees bearing fruit with healthy attributes.     

Genetic analysis of bread-making quality scores in bread wheat using a recombinant inbred line population

Bread-making quality has been evaluated in a progeny of 194 recombinant inbred lines (RILs) from the cross between the two French cultivars Récital and Renan, cultivated in three environments. These cultivars have been previously identified as having contrasting grain protein content and dough rheology properties, although they achieve similar scores for the official bread-making test used for cultivar registration in France. However the progeny displayed a wide range of variations, suggesting that favourable alleles at several loci are present in the two parental lines. Correlation analyses revealed that bread-making scores are poorly correlated among environments, as they are poorly predicted by multiple regression on dough rheology parameters and flour-protein content. However, loaf volume was the most heritable and predictable trait. A total of seven QTLs were found for bread scores, each explaining 5.9–14.6% of trait variation and six for the loaf volume (10.7–17.2%). Most bread-making QTLs, and particularly those detected in all environments, co-located with QTLs for dough rheology, protein content or flour viscosity due to soluble pentosans (Fincher and Stone 1986; Anderson et al. in J Cereal Sci 19:77–82, 1994). Some QTL regions such as those on chromosome 3A and chromosome 7A, which display stable QTLs for bread-making scores and loaf volume, were not previously known to host obvious genes for grain quality.     

Analysis of the gliadin multigene loci in bread wheat using nullisomic-tetrasomic lines

Summary The polypeptides specified by mRNAs hybridizing to several wheat storage protein cDNAs were determined by one-and two-dimensional gel electrophoresis of hybrid-selected translation products. Some of the polypeptides could be assigned to chromosomes on the basis of results gained from two-dimensional fractionation of the in vitro translation products of poly A⁺ RNA from nullisomic-tetrasomic lines of wheat. cDNA clones belonging to different hybridization groups contained sequences related to different gliadin polypeptide types. In order to determine the chromosomal location and copy number of homologous sequences in the wheat genome, selected cDNA clones were hybridized to restriction endonucleasedigested wheat DNA. The cDNA clones hybridized to sequences derived either from the group 1 chromosomes (-3 gliadin and pTag 544 type) or from the group 6 chromosomes (/, pTag 53 type). The / type sequences are present in 25–35 copies per haploid genome and pTag 544 type sequences in 10–15 copies per haploid wheat genome. Partial sequencing of some of the cDNAs revealed low level homology between the different gliadin cross-hybridization groups, a high-molecular-weight glutenin cDNA sequence and a clone encoding the barley storage protein B-hordein. The significance of these findings is discussed with respect to the probable ancestral relations between wheat endosperm storage protein genes.     

Genome-wide linkage disequilibrium analysis in bread wheat and durum wheat.

Bread wheat and durum wheat were examined for linkage disequilibrium (LD) using microsatellite markers distributed across the genome. The allele database consisted of 189 bread wheat accessions genotyped at 370 loci and 93 durum wheat accessions genotyped at 245 loci. A significance level of p < 0.001 was set for all comparisons. The bread and durum wheat collections showed that 47.9% and 14.0% of all locus pairs were in LD, respectively. LD was more prevalent between loci on the same chromosome compared with loci on independent chromosomes and was highest between adjacent loci. Only a small fraction (bread wheat, 0.9%; durum wheat, 3.2%) of the locus pairs in LD showed R2 values > 0.2. The LD between adjacent locus pairs extended (R2 > 0.2) approximately 2-3 cM, on average, but some regions of the bread and durum wheat genomes showed high levels of LD (R2 = 0.7 and 1.0, respectively) extending 41.2 and 25.5 cM, respectively. The wheat collections were clustered by similarity into subpopulations using unlinked microsatellite data and the software Structure. Analysis within subpopulations showed 14- to 16-fold fewer locus pairs in LD, higher R2 values for those pairs in LD, and LD extending further along the chromosome. The data suggest that LD mapping of wheat can be performed with simple sequence repeats to a resolution of <5 cM.     

Modeling and phylogeny analysis of bread wheat MnSOD

Superoxide dismutase (SOD) acts as first line of defense against oxidative and genetic stress. Manganese superoxide dismutase (MnSOD), found in mitochondria or peroxisomes, contains Mn(III) at the active site. Therefore, it is of interest to study MnSOD from bread wheat (a grain crop). However, a structure model is not yet solved for bread wheat MnSOD. Hence, we describe the structure model of bread wheat MnSOD developed using homology model. The model provides molecular insight to metal binding molecular function towards the understanding of oxidative stress resistance in plants. The distinction of bread wheat (a monocot) MnSOD from dicots is also shown using phylogenetic analysis.