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.     

Leaf and green area development of durum wheat genotypes grown under Mediterranean conditions

Future increases in the potential yield of wheat will require an improvement in the photosynthetic area in early growth stages. Our aim was to investigate the genotypic and environmental effects on the pattern of leaf and green area development of durum wheat (Triticum turgidum L. cv. durum). Twenty-five genotypes were grown during 2 years under irrigated and rainfed conditions in Lleida (northeastern Spain). Leaf area index (LAI) and green area index (GAI) were determined on eight occasions from seedling to maturity and data were fitted to an asymmetric logistic peak curve. Multivariate analysis of variance was used to assess the curve characteristics responsible for differences between years, sites and genotypes. Genotypic differences in the pattern of changes in LAI and GAI from sowing to maturity were not statistically significant, indicating a lack of genetic diversity for these traits in the germplasm used in this study. A decrease in the peak of the curves of 27% for LAI and 35% for GAI was observed under rainfed conditions compared to the irrigated site. Drought caused a lengthening of crop development until anthesis of about 2% (3–4 days). Contrarily, the time from sowing to the maximum LAI and GAI values were reduced by drought in around 10%, causing an acceleration of the onset of plant senescence. Once started, the senescence of the green organs of the plant was more rapid at the irrigated than at the rainfed site. It is concluded that LAI and GAI patterns were more influenced by the environment (mainly water availability) than by the genotype. The results suggest a certain degree of independent regulation for phenological development and the swiftness of green area accumulation in the plant.     

Variation in durum wheat populations from three geographical origins. I. Material and spike characteristics

Summary Sixteen durum wheat landraces. i.e. 6 from Algeria, 5 from Ethiopia and 5 from Italy were analysed in order to ascertain the amount of variation for all 11 spike characters. For each population the differences among spike progenies were significant for all the observed characters. Principal component analysis showed that 4 factors accounted for 80% of the total variation. Component 1 accounted for 32% of the total variation and was associated with spike width, spike density, number of kernels per spikelet and kernel weight. Component 2 accounted for 24% of the total variation and was associated with number of fertile spikelets, total number of spikelets and spike length. In a scatter diagram of all 1127 spike progenies for the first two principal components, the material from Ethiopia and Italy clustered at two opposite sides, while the material from Algeria had the largest swarm and overlapped the other two groups of material. Differences among populations from the same origin were found. The ecological and anthropological causes that may have played a role in the creation of the observed variation in the examined populations, are discussed.     

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.     

Environmental and genetic determination of protein content and grain yield in durum wheat under Mediterranean conditions

The unpredictability of the Mediterranean climate causes fluctuations in wheat yield and quality, but offers the opportunity for obtaining high‐quality durum wheat in terms of grain protein content. Twenty‐five durum wheat genotypes were grown under irrigated and rainfed conditions at each of two latitudes in Spain during 1998 and 1999. Differences between latitudes in grain protein content and chlorophyll content in the flag leaf were attributable to nitrogen fertilization management. Cycle length until anthesis was less affected by the environment than grain‐filling duration, and was longer under irrigated conditions than in the rainfed sites. A negative asymptotic curve was the best equation to fit the relationship between yield and protein content, suggesting that yield improvements in fertile environments may be attained with negligible reductions in protein content. ‘Jabato’, ‘Waha’, ‘Lagost‐3’, ‘Massara‐1’ and ‘Vit?on’ showed medium to high yield, yield stability and high protein content. Chlorophyll content in the flag leaf, measured at anthesis with the soil‐plant analysis development (SPAD) portable field unit, may be useful for the fast and cheap detection of durum wheat genotypes with high grain protein content in drought‐stressed Mediterranean environments.     

Genetics of yield, quality and shelf life characteristics in tomato under normal and late planting conditions

Seventy nine genotypes of tomato (15 lines, four testers and their 60 F₁ hybrids produced in line × tester fashion) were evaluated under normal (E₁) and late planting (E₂) conditions in the Department of Vegetable Crops, Punjab Agricultural University, Ludhiana, India, to determine the nature of gene action controlling yield, quality and shelf life characteristics and to identify a few good combiner genotypes which may be used in further breeding programmes to extend the fruit availability period of tomato in North Indian plains. The lines were significantly different from testers for most of the characters thereby justifying the choice of testers. Additive gene action was predominant for days to ripening, total yield per plant, marketable yield per plant, number of fruits per plant, average fruit weight, fruit shape index and lycopene in both the environments, whereas non-additive genetic variance predominated in controlling firmness index, number of locules, pericarp thickness, alcohol insoluble solids (AIS), dry matter, total soluble solids (TSS), titratable acidity, TSS:Acid ratio, pH, ascorbic acid and shelf life, under both normal and late planting conditions. The best general combining ability (gca) effects, among females, in respect of yield per plant were shown by Spectrum in E₁ and by LT-42 in E₂. Among the testers, the best gca values in both the environments were possessed by nor-RM-1 for total yield per plant, marketable yield per plant, number of fruits per plant, dry matter and TSS; by rin-RM-2 for firmness index, pericarp thickness and alcohol insoluble solids; by alc-IIHR-2050 for average fruit weight, number of locules and shelf life and by alc-IIHR-2052 for lycopene. The gca of ripening mutants had a nice consonance with their per se performance for most of the characters indicating that additive gene action was operative in these mutants for majority of the traits.     

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.     

Inheritance of resistance to the Russian wheat aphid in an Iranian durum wheat line

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a major economic pest of small grains in many countries. An experiment was therefore conducted to determine the inheritance of gene(s) controlling resistance to RWA in a resistant tetraploid durum wheat line. This resistant line,‘1881′, was crossed to a susceptible line, ‘Orejy‐e‐Kazeroon’, and then F₁ F₂ and BCF₁ (backcross to susceptible line) seedlings were screened in a greenhouse for RWA resistance following artificial infection. Resistance in ‘1881’ was apparently controlled by one dominant gene. Since Dnl, Dn2, dn3, Dn4 and Dn5 have been reported to be located on genome D, it was reasoned that the resistance gene in ‘1881’ is not allelic to them.     

Characterization and mapping of novel chlorophyll deficient mutant genes in durum wheat

The yellow-green leaf mutant has a non-lethal chlorophyll-deficient mutation that can be exploited in photosynthesis and plant development research. A novel yellow-green mutant derived from Triticum durum var. Cappelli displays a yellow-green leaf color from the seedling stage to the mature stage. Examination of the mutant chloroplasts with transmission electron microscopy revealed that the shape of chloroplast changed, grana stacks in the stroma were highly variable in size and disorganized. The pigment content, including chlorophyll a, chlorophyll b, total chlorophyll and carotene, was decreased in the mutant. In contrast, the chla/chlb ratio of the mutants was increased in comparison with the normal green leaves. We also found a reduction in the photosynthetic rate, fluorescence kinetic parameters and yield-related agronomic traits of the mutant. A genetic analysis revealed that two nuclear recessive genes controlled the expression of this trait. The genes were designated ygld1 and ygld2. Two molecular markers co-segregated with these genes. ygld 1 co-segregated with the SSR marker wmc110 on chromosome 5AL and ygld 2 co-segregated with the SSR marker wmc28 on chromosome 5BL. These results will contribute to the gene cloning and the understanding of the mechanisms underlying chlorophyll metabolism and chloroplast development in wheat.     

Inheritance of evapotranspiration and transpiration efficiencies in diallel F1 hybrids of durum wheat (Triticum turgidum L. var. durum)

Inheritance of water use and transpiration efficiency was studied in diallel F₁ hybrids from six cultivars of T. durum, selected for their different responses to drought stress. Plants were grown in 10 l pots at optimal (control) and low soil moisture levels in the glasshouse. GCA and SCA effects were significant at both soil moisture levels. Results demonstrated that evapotranspiration (ETE) and transpiration efficiency (TE) were under additive and dominant gene control. Interactions of GCA and SCA with moisture levels were also highly significant. GCA effects were the major components of the genetic variance of the biological and generative measures of ETE and TE. Narrow sense heritabilities for both ETE and TE based on grain yield were higher at the soil stress moisture level. Heritability estimates of ETE and TE based on the total biological yield, however, declined under the lower soil moisture level. Measures of ETE and TE showed significantly high and positive genotypic and phenotypic correlations among them as well as with grain yield and harvest index. In most cases, genotypic correlations were higher than phenotypic correlations. The results suggest that selection for high ETE and TE in terms of grain yield should be undertaken under both stress and optimal conditions. Selection in early segregating generations may lead to effective identification of desirable recombinants. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diversity of five glutenin loci within durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husn.) germplasm grown in Algeria

The HMW and B‐LMW glutenin subunits composition of 120 durum wheat germplasm grown in Algeria was examined using SDS‐PAGE. All together, 39 glutenin patterns were detected, including eight for HMW and 21 for B‐LMW glutenin subunits. Twenty‐six different alleles were identified for the five glutenin loci studied, that is, Glu‐A1 (3), Glu‐B1 (7), Glu‐A3 (5), Glu‐B3 (9) and Glu‐B2 (2). Two new alleles were found at Glu‐B3 locus: Glu‐B3new₁ encodes for five subunits (7 + 8 + 14 + 16 + 18) and Glu‐B3new₂ codes for five subunits (4 + 6* + 12 + 15 + 15*), of which subunit 15* with mobility between bands 15–16 was not described previously. At the Glu‐1 loci, the Glu‐A1c/Glu‐B1e allelic composition was predominant. For the B‐LMW glutenins, the most common allelic composition was Glu‐A3a/Glu‐B3a/Glu‐B2a. The collection analysed shows glutenin alleles and allele combinations related to high gluten strength. This information could be useful to select varieties with improved quality and also as a source of genes to develop new lines when breeding for quality.     

Estimation of grain yield by near-infrared reflectance spectroscopy in durum wheat

Near-infrared Reflectance Spectroscopy (NIRS) is widely used for routine, non-destructive assessment of grain quality in cereals. In this work, we assess the use of NIRS as an indirect indicator of grain yield (GY) in durum wheat grown in Mediterranean conditions. Plants were grown under rain-fed conditions in two sites in NW Syria, Breda and Tel Hadya, and a third trial was planted at Tel Hadya under support irrigation. We measured the spectral reflectance signature between 1100 and 2500 nm in flour from the same grains harvested for yield determination. By Partial Least Squares (PLSR), we obtained a model of the association between agronomic determinations of GY and these spectra. We found significant (p < 0.001) relationships between GY and NIRS-predicted values, with r ²= 0.36 (N= 96), r ²= 0.72 (N= 72) and r ²= 0.52 (N= 138) in Breda, and Tel Hadya rainfed and irrigated, respectively. Full cross validation of these models gave r ² between 0.31 and 0.33 (p < 0.001). When we applied the models to the samples from the other two trials, we found a general decrease in their predictive ability. Compared with other grain traits (carbon isotope discrimination, grain weight, ash and nitrogen content), NIRS showed a similar or even stronger relationship with GY, at least when validated in the same trial. We concluded that NIRS could be used to rank GY during the early generations of a breeding program, when performing yield trials is less feasible. However, further research is required to identify the environments in which this technique is more reliable, as well as to evaluate the heritability of NIRS-predicted GY.     

Analysis of adaptation of barley,triticale, durum and bread wheat under Mediterranean conditions

Summary Yield data obtained from a comparative small grain cereals trial, grown for five consecutive growing seasons at a total of 23 environments in Cyprus, were subjected to regression analysis. Within each environment, yield trials consisted of a standard set of three cultivars or elite lines of barley, triticale, durum and bread wheat. The regression coefficient (b) of crop mean on the environmental index (I) and the mean square deviation from regression (sd²) were calculated for each crop. Each crop tended to have its own characteristic value of sd² and its magnitude was an excellent indicator of specific crop-environment interaction. The causes of large sd², for two of the four crops, were the susceptibilith of barley to lodging, when favourable conditions were encountered at high yielding environments, and triticale dependence on late season precipitation. Durum wheat and triticale had an average response to different yielding environments (b>1.19) and both were significantly different from those of bread wheat (1.08) and barley (0.54). Hence, barley, bread and durum wheat are specifically adapted to low, average and high yielding Mediterranean environments, respectively. The cultivation of triticale at the expence of durum wheat is not feasible. Furthermore, interactions between crops and environments demonstrated by the regression parameters, should constitute the basis for decision making, regarding crop adaptation in a region. The average yield in all environments should not be considered as a proper criterion for adaptation. In this study, triticale had a similar mean grain yield (3,842 kg/ha) to that of bread wheat, but was significantly higher yielding than barley or durum wheat (5 and 7%, respectively).     

The occurrence and inheritance of a brittle rachis phenotype in Italian durum wheat cultivars

Italian and Tunisian durum wheats from different eras of breeding were assessed for the presence of a gene for brittle rachis. Nine of 15 Italian durum landraces had brittle rachides. Strampellis achievement was the release of the well-known variety, Senatore Cappelli, which was derived from a Tunisian landrace, Jenah Rhettifah, which has a brittle rachis. Rachides of two Tunisian landraces were also brittle. Since the 1950s, 16 accessions were released as selections from crosses or mutagenesis involving Senatore Cappelli. Seven of these accessions have brittle rachides. F₂ segregation in intercrosses of Senatore Cappelli with other durum accessions with brittle rachides indicated a common allele for brittle rachis. Segregation of the F₂ from Senatore Cappelli/ANW 10A and the F₂ of Senatore Cappelli/ANW 10B showed that the gene for brittle rachis of Senatore Cappelli was allelic to the brittle allele of the Br-B1 locus on chromosome 3B. Senatore Cappelli was presumably the only source of brittle rachis used in Italian breeding programmes. The genes for brittle rachis have been retained in the gene pool of durum wheat, suggesting that the brittle rachis character is not associated with an appreciable yield loss in modern farming systems in Mediterranean environments.     

Inheritance of β-carotene concentration in durum wheat (Triticum turgidum L. ssp. durum)

Despite being one of the important characteristics in determining pasta quality in durum wheat (Triticum turgidum ssp. durum), there is no direct report on inheritance of β-carotene concentration. The objectives of this study were to determine the inheritance of β-carotene concentration and the number of genes involved in six crosses of durum. For the cross PDW-233 (P₁) × Bhalegaon-4 (P₂), F₁, F₂, BCP₁ and BCP₂ populations were developed. For all other crosses, only the F₁ and F₂ populations were developed. β-carotene concentration was determined for all populations and parents of each cross grown at Hol, Maharastra, India. The cross PDW-233 × Bhalegaon-4 was also evaluated at Dharwad, Karnataka, India. Low β-carotene concentration was partially dominant in most of the crosses. Broad sense heritability was 67 and 91% at Dharwad and Hol, respectively, for the cross PDW-233 × Bhalegaon-4 and varied from 74 to 93% for the other five crosses indicating the presence of additive gene effects. The frequency distributions of the trait in the F₂ populations were not normal and were skewed towards the lower parent. Segregation of β-carotene concentration in the six F₂ populations indicated that at least two major genes and two or three minor genes with modifying effects govern the trait. Analysis of variance indicated that environment had comparatively little influence on the trait and this should allow for easy selection. The joint scaling test revealed additive × additive, additive × dominance and dominance × dominance epistatic interactions in the cross PDW-233 × Bhalegaon-4. These authors contributed equally.     

Biodiversity in a germplasm collection of durum wheat

Summary Over 7,600 durum wheat accessions belonging to 22 country gene pools were evaluated in Syria, during the seasons 1985–86 through 1987–88 under semi-arid Mediterranean climatic conditions. Data on seven agronomic traits are presented to assess the distinctiveness and the phenotypic diversity of these pools. Univariate statistical analysis revealed differences among materials of diverse origins for all traits. Mean phenotypic diversity within countries was highest in the germplasm from India, lowest in that from Bulgaria. In a canonical variate analysis, the first three canonical variables explained 77.7% of the total variance. A cluster analysis was performed to supplement the generated information by the canonical analysis. The multivariate analyses evidenced the distinctiveness of the Ethiopian germplasm. The gene pools from Syria and Jordan, closely resembling each other, appeared separate from all others. A certain peculiarity was also shown by the germplasms from Greece, Morocco and France, while the remaining countries clustered into four groups. The results of the present evaluation could provide useful information for breeding activities, germplasm collection, and establishment of core collections. Evidence is presented that environment played a major role in creating the overall variation for the considered traits, although germplasm exchange seemed also an important factor.     

Inheritance of resistance to yellowberry in durum wheat

Resistance to grain yellowberry in durum wheat (Triticum durum Desf.) was investigated using generation mean analysis in four resistant or intermediate-resistant X susceptible crosses. Significant differences in resistance were observed between generations in all crosses. Generation mean analysis indicated a complex gene action controlling this trait, with additive, dominance and epistatic effects. Additive (d) components were positive in all crosses, suggesting that additive effects contributed more to resistance than to susceptibility. In contrast dominance (h) effects were negative in majority of crosses. The minimum number of genes controlling resistance was estimated at 1.41. Mid-parent heterosis ranged from 28.5 to 52.1 indicating dominance of resistance. Broad-sense heritability estimates ranged from 0.52 to 0.88, while narrow-sense heritability estimates ranged from 0 to 0.79. Estimates of genetic gain for resistance ranged from low to high. Estimates of broad and narrow sense heritabilities indicated that genetic effects were larger than environmental effects. Additive effects represented the largest components of genetic effects.     

New durum wheat with Hessian fly resistance from Triticum araraticum and T. carthlicum in Morocco

Hessian fly is an important pest of wheat on the North American continent and the temperate Mediterranean drylands. Yield losses caused by this insect in Morocco are the heaviest in the Mediterranean region and are estimated to be 36% on average. Genetic resistance to Mediterranean Hessian fly biotypes has not been found in durum wheat, although large numbers of durum accessions were screened. Genes for resistance were found in common wheat; some of which are transferable to durum. However, there is a need to broaden the genetic base for resistance in durum wheat. The objective of this work was to introgress resistance from selected Triticum araraticum and T. carthlicum accessions using multiple backcross methodology. The experimental recipient durum wheat included numerous adapted and high‐yielding lines. Testing for Hessian fly resistance under controlled conditions and field yield data showed that this programme yields Hessian fly‐resistant durum lines with good yields and adaptation.     

Morpho-physiological traits to complement grain yield selection under semi-arid Mediterranean conditions in each of the durum wheat types mediterraneum typicum and syriacum

Summary Some 238 landraces from Algeria and Tunisia representative of the mediterraneum typicum durum wheat type and 265 landraces from Syria and Jordan representing the syriacum type were grown in a semi-arid Mediterranean environment of Northern Syria characterized by moderate drought stress. The germplasm types were compared for mean value, level of variation and relationships with grain yield of various morpho-physiological traits possibly usable for indirect selection of best yielding materials. The syriacum germplasm showed higher yield mainly due to greater earliness of cycle, slightly longer grain filling period, shorter stature, lower early growth vigour and higher drought tolerance expressed by a visual score recorded in another, more stressful environment in the region. It also showed lower variation for all morpho-physiological characters except plant glaucousness, for which it was more variable. The wheat types differed not only for architecture but also for optima of individual morpho-physiological traits required to maximize the yield response in the given environment. Higher yield of syriacum materials was attained at same heading and three to four days delayed maturity with respect to average phenology of three well-adapted control cultivars, and it was favoured by increasing number of kernels per spike, early vigour and drought tolerance. Higher yield of mediterraneum typicum landraces was related to heading and maturity dates approaching those of the control cultivars and to increasing kernel weight, early vigour and drought tolerance. Plant stature hardly affected the yield. Both absent and strong glaucousness could confer a yield advantage in syriacum materials.     

Nitrogen uptake and nitrogen harvest index in durum wheat cultivars varying in their grain protein concentration

Summary In a field experiment, plant (excluding roots) and grain nitrogen at harvest were estimated in 15 durum wheat cultivars varying in their grain protein concentration. They showed significant variation in grain yield, grain protein concentration, biological yield, total plant nitrogen at harvest and residual nitrogen in straw. Harvest index and nitrogen harvest index were calculated from this primary data. Nitrogen harvest index varied from 57 to 83%. Plant nitrogen showed significant positive correlation with biological yield, grain yield and grain protein yield, but the correlations with grain protein concentration, harvest index and nitrogen harvest index were not significant. Nitrogen harvest index was positively correlated with harvest index indicating that the distribution of N between straw and grain to a large extent, but not entirely, depends upon the partitioning of dry matter between the two. Grain protein concentration was neither correlated significantly to plant nitrogen nor to nitrogen harvest index.