Origin and variation of gliadin proteins associated with pasta quality in durum wheat

Summary Studies were made of the presence and frequency of occurrence of gliadin bands 42 and 45 in three samples of Aegilops sharonensis Eig and 59 samples of wild tetraploid wheat (Triticum dicoccoides Korn.) from natural distributions of these species in Israel.Two samples of Ae. sharonensis possessed a band in position 45 and one possessed no bands corresponding to either band 45 or band 42. In T. dicoccoides, band 45 was either present or not and 42 was always absent. In its grassy and intermediate growth habit forms, (believed to be more primitieve than the cercal forms) band 45 appeared to be more frequent than in the cereal form.The presence of band 45 in the Ae. sharonensis, and its relatively high frequency in T. dicoccoides, populations from Mt. Hermon (likely to be relatively free from introgression from cultivated tetraploid wheat) indicate the likelihood of a primary origin of the allele coding for band 45. The absence of band 42 from all Ae. sharonensis and T. dicoccoides populations in this study, indicates a more recent evolutionary origin of the allele coding for this band, possibly arising as a mutation during the domestication of tetraploid wheat.The results have implications for breeding programmes in tetraploid wheat.     

Discriminating durum wheat cultivars using highly polymorphic simple sequence repeat DNA markers

The winter type durum wheat varieties of Anatolia used in this study were differentiated for the first time by using simple sequence repeat (SSR) DNA markers or microsatellites. Seven microsatellite markers were used to distinguish four well‐adapted landrace selections, five cultivars and seven recently obtained advancing lines. The loci of seven microsatellites were all homozygous, but the WMS6 locus occurred with two alleles in all the genotypes. The genotypes were all distinguished from each other, with the number of alleles ranging from five to 13. The lowest and highest polymorphism information content (PIC) values were observed to be 0.609 and 0.872, respectively. Three markers alone, WMS6, WMS30 and WMS120, can distinguish all 16 genotypes. UPGMA dendogram, based on a similarity matrix by a simple matching coefficient algorithm, is in accordance with the available pedigree information.     

SPAD readings and associated leaf traits in durum wheat, barley and triticale cultivars

SPAD readings may represent a useful screening criterion in breeding programs aimed at increasing the rate and duration of leaf photosynthesis. A two-year trial was conducted on 17 cultivars of durum wheat, 8 of triticale and 18 of barley at two experiment stations in Sardinia, Italy, to evaluate the existence of genetic variation for SPAD readings, and to quantify the genetic associations between SPAD readings, area per leaf blade (LA), specific leaf area (SLA), leaf nitrogen concentration (LNC) and leaf nitrogen per unit of leaf surface (LN) in the period between beginning of tillering and flag leaf appearance. Plants were grown at sufficient nitrogen fertilization. The average SPAD reading of barley was 9–10 units lower than that of durum wheat and triticale. The combined ANOVA indicated that, in all the three species, the genotype by environment interaction variance associated with SPAD readings was lower than the genetic variance. In durum wheat and barley, SPAD readings exhibited a greater genetic variance in comparison with LNC, LN and SLA. In durum wheat and triticale, SPAD readings were genetically correlated with LN and SLA. Durum wheat differed from triticale because its genetic variation in SLA was not associated with LA. A screening based on both SPAD readings and LA values should identify lines with good photosynthetic machinery that is not associated with low area per leaf blade. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breeding durum wheat for pasta quality in Canada

Canada was the largest durum wheat (Triticum turgidum var durum) producer in 1994, and in recent years supplied over 70% of world export trade in durum. Breeding for pasta quality is, therefore, a primary objective in Canadian durum breeding programs. Control of cultivar registration and stringent grading standards ensure that durum of consistent high quality is produced for domestic and export markets. The objectives of breeding programs include: improvement of traits related to production concerns, such as grain yield, disease resistance and sprouting resistance, and those related to end-use quality, such as protein concentration and quality; milling quality factors, such as semolina yield; colour of the wheat, semolina and pasta; and cooking quality. Selection and testing for quality begins at very early generations and becomes more stringent for advanced inbred lines. Selection is practised at the F₁ or F₂, where appropriate, using monoclonal antibodies to identify desirable gamma gliadins (γ-45 ) or low molecular weight glutenin subunits (LMW 2) that have been shown to be related to end-use quality. Grain from early generation yield trials, starting at F₄, is screened for protein concentration and pigment content by Near Infrared reflectance, and for gluten strength by sodium dodecyl sulphate (SDS) sedimentation and micro-mixograph. Promising lines entered into multi-location yield trials are screened with more time-consuming procedures to fully assess suitability for pasta processing. These tests include semolina yield, ash and colour, and predictions of gluten strength such as mixograph and alveograph, and cooking quality. Candidate cultivars with quality equal to or better than the mean of the check cultivars can be proposed for registration after three years in the Durum Cooperative Test. It takes approximately 10 years from performing a cross to registrating a new cultivar. This revised version was published online in August 2006 with corrections to the Cover Date.     

Breeding for yield and quality in durum wheat

Three populations of an intervarietal durum wheat cross IWP5308/PDW208, F₅, F₅BIP₁ (population derived after intermating in F₂) and F₅BIP₂ (population derived after intermating in BIPF₁), were evaluated under three different agronomic environments for mean performance and stability of genotypes for grain yield, yield components and protein content. Though the biparental progenies indicated a higher mean performance, they did not differ significantly from progenies of the pedigree method for almost all characters. The biparental progenies, however, produced a higher number of stable genotypes for grain yield per plant, grains per ear and protein content. The F₅ population had a higher number of stable genotypes for 1000 grain weight and number of tillers per plant. The BIP progenies also had a higher number of genotypes with above average mean performance, and many were significantly higher than the checks WH896 and WH542, compared with F₅ progenies. Hence, in spite of high G x E interactions, the use of cycles of biparental mating and selection of top yielding lines on the basis of yield components can enable selection of stable genotypes with high protein content. Number of tillers per plant and 1000 grain weight were the yield component characters which made maximum contribution to phenotypic stability of the genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationships among adaptation patterns, morphophysiological traits and molecular markers in durum wheat

Breeding for specific or wide adaptation would be more cost-efficient if preliminary indications on genotype adaptive responses could be provided by easily-detectable morphophysiological or molecular characteristics. We investigated the consistency among adaptation parameters, morphophysiological traits and SSR markers in estimating and structuring the genetic diversity among 24 durum wheat genotypes. Additive main effects and multiplicative interaction adaptation parameters were estimated across 14 Algerian locations belonging to a low- or a high-elevation subregion. Eight morphophysiological traits were assessed in two locations per subregion. Genotype Euclidean distances based on adaptation parameters were closely related to those based on morphophysiological traits ( r  = 0.75, P = 0.01). Marker-based distances exhibited low correlation with those based on adaptation parameters ( r  = 0.26, P = 0.01) or morphophysiological traits ( r  = 0.32). The consistency between adaptation parameters and morphophysiological traits for genotype ordination and classification was greater than that between either information layer and SSR markers. Optima of phenology and plant height differed between subregions, whereas many kernels per spike and fertile tillers were associated with adaptation to both subregions.     

Genetic changes in durum wheat yield components and associated traits in Italian and Spanish varieties during the 20th century

Twelve field experiments comparing 24 durum wheat varieties from three periods—old (<1945), intermediate (1950–1985) and modern (1988–2000)—were carried out in order to ascertain the advances made in durum wheat yield components and related traits in Italian and Spanish germplasm. Grain yield improvements were based on linear increases in the number of grains per m² and harvest index, while grain weight and biomass remained unchanged. Yield per plant increased at a rate of 0.36 and 0.44% y⁻¹ and the number of grains per m² improved by 39% and 55% in Italian and Spanish varieties, respectively. The mean rate of increase in the number of grains per m² was 0.55% y⁻¹. Plants per m², spikes per plant and grains per spike contributed 20%, 29% and 51%, respectively, to the increase in the number of grains per m². The enhance of the number of grains per m² was due to the greater grain set in the modern varieties, since the number of spikelets per spike remained unchanged. Harvest index increased overall by 0.48% y⁻¹ (0.40 and 0.53% y⁻¹ in Italian and Spanish varieties, respectively). Plant height was the trait that suffered the most dramatic changes (it decreased at a rate of −0.81% y⁻¹, with little difference between the varieties of the two countries), as consequence of the presence of the Rht-B1 dwarfing gene. Harvest index and plant height, which were the traits that most contributed to discriminating between periods, remained unchanged from 1980 to 2000. The higher rates of improvement in Spain are discussed in the context of the contrasting strategies followed to improve durum wheat yield in the two countries.     

QTL analysis of main and epistatic effects for flour color traits in durum wheat

The aim of this work was to map quantitative trait loci (QTLs) associated with flour yellow color (Fb*) and yellow pigment content (YPC) in durum wheat (Triticum turgidum L. var. durum). Additionally, QTLs affecting flour redness (Fa*) and brightness (FL*) color parameters were investigated. A population of 93 RILs (UC1113 × Kofa) was evaluated in three locations of Argentina over 2 years. High heritability values (>94%) were obtained for Fb* and YPC, whereas FL* and Fa* showed intermediate to high values. The main QTLs affecting Fb* and YPC overlapped on chromosome arms 4AL (4AL.2), 6AL (6AL.2), 7AS, 7AL, 7BS (7BS.2) and 7BL (7BL.2). The 7BL.1 QTL included the Psy-B1 locus, but one additional linked QTL was detected. A novel minor QTL located on 7AS affected Fb*, with an epistatic effect on YPC. An epistatic interaction occurred between the 7AL and 7BL.2 QTLs. The 4AL.2 QTL showed a strong effect on Fb* and was involved in two digenic epistatic interactions. The 6AL.2 QTL explained most of the variation for Fb* and YPC. The main QTLs affecting FL* and Fa* were located on 2BS and 7BL, respectively. These results confirm the complex inheritance of flour color traits and open the possibility of developing perfect markers to improve pasta quality in Argentinean breeding programs.     

Variation in endosperm protein composition and technological quality properties in durum wheat

Durum wheat quality is controlled by endosperm protein content and composition. Electrophoretic, protein content and SDS sedimentation analyses were carried out on a large collection of accessions of durum wheat from Turkey, and compared with Italian cultivars. A number of patterns were detected, resulting from the combination of different alleles at genomes A and B, and new allelic variants were identified. Genotypes with the same allele at Gli-B1 showed inconsistencies in the comparison of low molecular weight glutenin subunits (LMW-GS), suggesting caution in considering γ-gliadins as genetic markers for pasta quality. Variation in protein content and SDS sedimentation values was wider in the Turkish material than in the Italian cultivars, the values of which were in line with cultivars from Australia, Canada, France, and the USA. A substantial amount of the variation in gluten properties was explained in terms of protein composition, with LMW-GS making the largest contribution. Reversed phase high performance liquid chromatography (RP-HPLC) analyses were carried out on two biotypes of the Italian cultivar Lira that differ at the Gli-B1/Glu-B3 loci (Lira 42 has γ-42, LMW-1, and poor quality; whereas Lira 45 has γ-45, LMW-2, and good quality). The results indicated that differences in quality may be due to: 1) the absolute amount of LMW glutenins which was greater in LMW-2; 2) the relative predominance of LMW-s type and LMW-m type subunits in Lira 45 glutenins which act as polymer chain extenders; and 3) the higher proportion of the α-type and γ-type glutenin subunits, in Lira 42 glutenins, which have an additional (nine) cysteine residue in the N-terminal region and act as glutenin chain terminators. The conclusion reached was that breeding for quality should consider selection for LMW-GS and against α-type and γ-type glutenin subunits. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physiological attributes associated with yield and stability in selected lines of a durum wheat population

Further increasing yield potential remains one of the main objectives of wheat breeding, even in stressful environments. In general, past genetic gains were associated with increases in harvest index, and future gains should be related to greater biomass. Identifying genetic sources for such improvement may be relevant. Researchers of TRITIMED identified DH lines of durum wheat apparently possessing not only high yield potential but also good yield stability. We aimed to determine physiological attributes responsible for yield and stability among a set of genotypes derived from two parents (Cham 1 and Lahn) and four of the most promising lines of the DH population (2401, 2408, 2410, 2517). Seven field trials were carried out within the Mediterranean agricultural region of the Ebro Valley, under a wide range of conditions (ca 2–10 mg ha⁻¹). In four of these experiments, sub-plots were included with source-sink manipulations imposed after anthesis. Cham 1, a cultivar known for high yields in semi-arid conditions, showed the highest yield potential. Although it showed less yield stability than Lahn, even under the lowest yielding conditions its yield was not significantly lower than that of Lahn. RILs 2408, 2410, 2004 and 2517 slightly outyielded Lahn in high-yielding conditions, but under poorer environments they tended to yield less. Interestingly, yield differences were closely related to their biomass rather than harvest index. Thus yield differences relating to the number of grains per m² were due to differences in spike dry matter at anthesis, reflecting in part genotypic differences in crop growth from jointing to anthesis. In general grain weight did not respond to spike trimming after anthesis, although in two experiments the grain weight of Cham 1 did so. Thus, even the highest-yielding cultivar possessed grains that overall seemed more limited by its constitutive capacity to grow than by the availability of resources to reach this capacity (though occasionally they may be co-limited). Overall, the most interesting feature was the empirical evidence that improvement of biomass within elite material is a worthwhile objective.     

Morphological attributes associated with early-season drought tolerance in spring durum wheat in a mediterranean environment

Impacts of drought during the reproductive development phase of wheat have been thoroughly investigated, while studies of the early-season drought effects are lacking. Field experiments were conducted to study the effect of duration of drought stress during the period from emergence to the end of tillering on the growth and performance of different wheat cultivars, and to identify traits that could be associated with the resistance to early season drought. Experiments were conducted on a Vertic Calcixerol soil in the semiarid cereal-growing region of Morocco in 1995 and 1996. Six spring durum wheat (Triticum durum Desf.) cultivars selected on the basis of variation in morphology, phenology, and zone of adaptation were subjected to four water regimes, including a well-irrigated control. The three water stress treatments were imposed by withholding water during the period from emergence to either the onset, middle, or the end of tillering. Subsequent irrigations provided adequate soil moisture for the remainder of the growing season. Results from both years were generally consistent. The differential responses of the six cultivars was mainly due to differences in numbers of kernels produced. High yields under early-season drought were attributed to high leaf area index under stress and, upon recovery, and to high tiller survival rate. The consistency observed over years in the relationships between grain yield and those traits that proved to be most associated with the resistance to early-season drought, would suggest the usefulness of these traits as selection criteria for breeding for improved drought resistance in a Mediterranean climate type of North Africa. This revised version was published online in July 2006 with corrections to the Cover Date.     

江苏省优质软麦品种品质特性与饼干加工品质的关系

明确软麦品种在大田生产中的品质表现和品质育种筛选指标,对于优质生产及提高育种效率具有重要意义。选用江苏淮南麦区15份优质软麦品种(系),鉴定其高分子量麦谷蛋白亚基(HMW-GS)组成,开展3个试验点次的大田种植,分析了小麦样本的籽粒硬度、灰分含量、蛋白质含量和质量参数、粉质仪参数、揉面仪参数、溶剂保持力、贮藏蛋白组分含量参数、黏度仪参数等品质性状和饼干加工品质。结果表明,不同类型的品质参数受基因型和环境的影响不同。所有样本的蛋白质含量、湿面筋含量、稳定时间均不达国标(GB/T 17320-2013、GB/T 17893-1999),部分品种(系)的沉淀值达标,所有样本的籽粒硬度和吸水率全部达标。相关性分析表明,籽粒硬度、灰分含量和黏度仪参数与饼干加工品质无显著相关性。沉淀值、粉质仪吸水率、粉质仪稳定时间、揉面仪峰值时间、揉面仪衰落角、水溶剂保持力、碳酸钠溶剂保持力、乳酸溶剂保持力、谷蛋白/醇溶蛋白比、不溶性谷蛋白含量和不溶性谷蛋白百分含量与饼干直径呈显著(r≤–0.520)或极显著(r≤–0.652)负相关,相关系数分别为–0.657、–0.601、–0.617、–0.659、–0.6...     

Relationships between different prolamin proteins and some quality properties in durum wheat

The objective of this paper was to study the differences between some prolamin variants coded at the loci Glu-3/Gli-1, Glu-1 and Gli-A2 and their relative roles in durum-wheat quality. F₃ lines from four durum wheat crosses (‘Abadia’בMexicali’. ‘Oscar’בArdente’, ‘Oscar × Mexicali’ and ‘Alaga’בC. of Balazote’) were analysed for gliadin and glutenin composition by electrophoresis. Whole-grain-derived samples were analysed for SDS sedimentation (SDSS) value, mixing properties, and contents of protein and vitreousness. The glutenin patterns LMW-2. LMW-2^? and LMW-2 (CB) at Glu-B3/Gli-B1 were associated with better gluten quality than were LMW-1 and LMW-2*. The glutenin subunits LMW4 and LMW3 + 15 at Glu-A3/Gli-A1 and HMW-1 showed better mixing properties than LMW7 + 12, LMW5 and the null phenotype. respectively. The HMW glutenin subunits 20 + 8 at Glu-B1 showed a negative association with gluten quality, but the rest of the HMW glutenin subunits and α-gliadins did not show any influence on gluten quality. Correlations between the results of the SDSS test and the mixograph were highly significant, but no correlation was found between these results and protein and vitreousness contents. The results are discussed in relation to the development of durum wheat varieties with improved qualities.     

Evaluation of end use quality and root traits in wheat cultivars associated with 1RS.1BL translocation

1RS.1BL translocation in wheat, exploited for its multiple disease resistance (Lr26, Yr9, Sr31 and Pm8), has  maintained significance due to its agronomical advantages. However, this translocation exhibits serious defects in dough quality due to the presence of Sec-1 loci on 1RS arm. In the present investigation micro SDS sedimentation test (MST), high molecular weight glutenin subunits (HMWGS) and bread making analysis of 26 genotypes were studied along with their root phenotyping in the field and under hydroponic culture system. The MST values showed that genotypes having Sec-1 loci had low MST values but in the presence of Glu-D1 (5?+?10) with Glu-B1 (7?+?9) and (7?+?8) they had high MST values, thus overcoming the negative effects of secalin on dough quality. The loaf volume showed positive correlation with MST values of the genotypes. The translocation of 1RS arm led to higher root biomass and longer root length than Pavon 76 without 1RS. Better root traits in recombinant 1RS 44:38 and 1B?+?38 than Pavon 1RS.1BL suggested the role of negative epistatic effects between different QTL regions in 1RS arm. The results suggest that it should be possible to harness the useful alleles associated with good dough quality, better root traits, high yield and stress tolerance with or without secalin.     

Inheritance of cleistogamic flowering in durum wheat (Triticum durum)

Summary Generally durum wheat flowers are chasmogamous but very rarely, cleistogamy may be observed. Genetic studies based on six crosses and back crosses showed that chasmogamy was determined by a single dominant gene Cl, plants homozygous for the recessive allele, cl, were cleistogamous. The flowering behaviour phenotypes were unaffected by environmental conditions. Cleistogamy was attributed to poorly developed lodicules and stiff perianth.     

Quantitative trait locus analysis of wheat quality traits

Milling and baking quality traits in wheat (Triticum aestivum L.) were studied by QTL analysis in the ITMI population, a set of 114 recombinant inbred lines (RILs) generated from a synthetic-hexaploid (W7985) × bread-wheat (Opata 85) cross. Grain from RILs grown in U.S., French, and Mexican wheat-growing regions was assayed for kernel-texture traits, protein concentration and quality, and dough strength and mixing traits. Only kernel-texture traits showed similar genetic control in all environments, with Opata ha alleles at the hardness locus Ha on chromosome arm 5DS increasing grain hardness, alkaline water retention capacity, and flour yield. Dough strength was most strongly influenced by Opata alleles at 5DS loci near or identical to Ha. Grain protein concentration was associated not with high-molecular-weight glutenin loci but most consistently with the Gli-D2 gliadin locus on chromosome arm 6DS. In Mexican-grown material, a 2DS locus near photoperiod-sensitivity gene Ppd1 accounted for 25% of variation in protein, with the ppd1-coupled allele associated with higher (1.1%) protein concentration. Mixogram traits showed most influence from chromosomal regions containing gliadin or low-molecular-weight glutenin loci on chromosome arms 1AS, 1BS, and 6DS, with the synthetic hexaploid contributing favorable alleles.Some RI lines showed quality values consistently superior to those of the parental material, suggesting the potential of further evaluating new combinations of alleles from diploid and tetraploid relatives, especially alleles of known storage proteins, for improvement of quality traits in wheat cultivars.Contribution number 06-77J from the Kansas Agricultural Experimental Station.     

Phenotypic divergence for morphological and yield-related traits among landrace genotypes of durum wheat from Jordan

Summary Landrace genotypes of durum wheat, from 10 districts in Jordan, have been evaluated for 18 morphological and yield related traits. Results of multivariate analysis, including analysis of variance, cluster analysis and canonical discriminant analysis, indicate that the magnitude of phenotypic divergence in these landrace genotypes is large, especially when compared with a world collection of durum wheat. These results provide an experimental evidence for phenotypic differentiation as a result of variation in altitude and long-term average rainfall of collection sites, but not on the basis of district of collection. R²-values for fit to least squares model ranged from 67.0–78.0%, and from 18.5–30.0%, for the first and second cases, respectively. Landrace genotypes from different districts formed 5 clusters on the basis of altitude and long-term average rainfall of collection site. Three canonical factors accounted for 92% of total variance in these clusters. The first canonical factor accounted for 57% of total variance and was mainly correlated with spike length, awn length and spikelets/spike. The second canonical factor accounted for 22% of total variance and was positively correlated with peduncle length, seed weight per plant, kernel weight and ratio of peduncle length to plant height. However, it was negatively correlated with awn length. The phenotypic diversity found in these landrace genotypes could help identify genetically different genotypes for durum wheat improvement.     

Genetic relationships of Brassica vegetables determined using database derived simple sequence repeats

Sequence databases were screened to identify simple sequence repeats (SSRs) in Brassica oleracea sequences. A total of 512 B. oleracea DNA sequences were screened and 43 potential SSRs were identified. Thirty-six primer pairs were designed to amplify target sequences. Of the 36 primer pairs, six failed to amplify fragments of expected sizes, and 17 primer pairs failed to generate polymorphisms. Thirteen SSRs were used to assess genetic similarity between 54 B. oleracea cultivars, belonging to 3 variteal groups (cabbage, cauliflower, and broccoli). Pairwise genetic similarities were calculated for cultivars, and a dendrogram of relationships was produced. All cabbage cultivars were distinguished from each other and clustered in two separate groups. Five cauliflower cultivars could not be distinguished with SSR markers used in the study. Three broccoli cultivars clustered with cauliflower cultivars, and two cauliflower cultivars grouped with broccoli cultivars. The varietal group with the narrowest genetic variation in the study was cauliflower (B. oleracea var. botrytis) followed by broccoli (B. oleracea var. italica) and cabbage (B. oleracea var. capitata) groups. Polymorphism information content (PIC) values and number of alleles produced per marker ranged between 0.25 to 0.86 and 1 to 8, respectively, for database derived SSR markers.     

Genetics of spike length in durum wheat

Gene effects were analyzed using mean spike length of 12 populations, viz., both parents, F₁, F₂, first back cross generation, BC₁ and BC₂, second backcross generations, BC₁₁,BC₁₂, BC₂₁ and BC₂₂ along with BC₁ self and BC₂ self derived by selfing BC₁ and BC₂populations of three crosses involving six diverse cultivars of Triticum durumto determine the nature of gene actions governing spike length through generation mean analysis under normal and late sown environments. The six-parameter model was adequate in most of the cases to explain genetic variation among the generation means under both the sowing environments. Additive (d) gene effect was significant in all the cases, whereas dominance (h) gene effect was not so frequently observed significant. Epistatic effects, particularly digenic types were predominant over additive and dominance effects in most of the cases under both normal and late sown environments except in the cross Cocorit 71 × A-9-30-1 (normal sown).Additive × dominance × dominance (y), trigenic interaction played significant role in controlling the inheritance of this trait in the cross HI 8062 × JNK-4W-128under late sown condition. Duplicate epistasis was observed in the cross HI 8062× JNK-4W-128 (normal sown). Non-fixable gene effects were of higher magnitude than fixable gene effects in almost all cases, confirmed the major role of non-additive gene effects to control the inheritance of spike length in durum wheat. Significant heterosis over better parent was not observed. Similarly, inbreeding depression was not commonly observed. Favourable and suitable environment must be considered before finalizing breeding programme for its simple inheritance to get desirable improvement for high grain yield. Hybridization systems, such as biparental mating and / or diallel selective mating, which exploit both additive and non-additive gene effects, simultaneously, could be useful in the improvement of spike length in durum wheat. This revised version was published online in July 2006 with corrections to the Cover Date.