Durum Wheat Landraces Research Articles

Ear photosynthesis, carbon isotope discrimination and the contribution of respiratory CO2 to differences in grain mass in durum wheat

ABSTRACTThe role of ear photosynthesis in grain filling was studied in a number of durum wheat (Triticum turgidum var durum L.) landraces and varieties from the Middle East, North Africa, and from the collections of ‘Institut National de la Recherche Agronomique’ (INRA, France) and ‘Centro International de Mejora de Maiz y Trigo’ (CIMMYT, Mexico). Plants were grown in the field in a Mediterranean climate. Flag leaves (blade plus sheath) and ears were kept in the dark from 1 week after anthesis to maturity which reduced grain weight by 22.4% and 59.0%, respectively. In a further experiment, the carbon isotope discrimination ratio (Δ) of ear bracts, awns and flag leaves was measured on samples taken at anthesis and on mature kernels. The mean value of Δ for the water soluble fraction of bracts (17.0‰) and awns (17.7‰) were lower than those of leaves (19.5‰) and fairly similar to those of kernels (17.4‰) averaged across all genotypes. Data indicate that most of the photosynthates in the grain come from ear parts and not from flag leaves. In addition, a higher water use efficiency (WUE) of ear parts than of the flag leaf is suggested by their lower Δ values. Gas exchange in ears and flag leaves was measured during grain filling. Averaged over all genotypes, CO2 diffusive conductance was about five times higher in the flag leaf than in the spike (with distal portions of awns outside the photosynthetic chamber) 2 weeks after anthesis. In absolute terms, the dark respiration rate (Rd) was greater than the net photosynthesis rate (Pn) by a factor of 1.74 in the spike, whereas Rd was much smaller, only 22.1, 65.7 and 24.8% of Pn in blade, sheath and awns, respectively. Data indicate that photosynthesis, and hence the water use efficiency (photosynthesis/transpiration), is greatly underestimated in ears because of the high rates of respiration which diminish the measured rates of net CO2 exchange. Results of 13C discrimination and gas exchange show that genotypes from North Africa have higher WUE than those from the Middle East. The high Rd values of ears as well as their low diffusive conductance suggest that CO2 from respiration may be used as source of carbon for ear photosynthesis. In the same way, the anatomy of glumes, for example, supports the role of bracts using internal CO2 as source of photosynthesis. In the first experiment, the Δ in mature grains from culms with darkened ears compared with control culms provided further evidence in support of this hypothesis. Thus, the Δ from kernels of control plants was 0.40 higher than that from ear‐darkened plants, probably because of some degree of refixation (recycling) of respired CO2 in the grains.

Grain Yield and Quality of Durum Wheat Landraces in a Dry Mediterranean Region of Northern Syria

AbstractTwenty‐two durum wheat landraces of various origins were evaluated for performance and stability of grain yield, protein content and gluten strength (SDS sedimentation volume) at two sites of Northern Syria situated in the drought‐prone part of the local durum wheat belt. Yield was recorded in three seasons, while protein content and SDS volume were assessed in two seasons only. A high “entry X environment” interaction was observed for all traits, which was significantly attributable to heterogeneity of entry regressions on the environmental mean for grain yield only. Compared to the recently‐bred, widely‐grown variety ‘Sham I’, some landraces showed somewhat similar yield responses, whereas others proved more stable without being significantly lower yielding. Significant variation was found for SDS volume, though only few of the best‐ranking landraces for this trait also possessed an acceptable yield level. The entries did not significantly differ for protein content. The broad sense heritability estimates obtained for grain yield (0.59) and SDS volume (0.89) highlighted the interest in some of the landraces examined for improving grain yield and quality in the region.

Field evaluation and simulation of frost tolerance in Syrian durum wheat landraces

Forty-nine Syrian durum wheat landraces were sown in late Nov. 1989 at Tel Hadya, Syria (a low-yielding site) and 38 were sown in mid-Dec. at Homs (a high-yielding site) with or without N + P fertilizer. Jan. frosts caused less than 5% apparent foliar damage in any of the landraces. However, foliar damage by Mar. frosts averaged 23% (range 3-65%). Late frost tolerance of foliage appeared to be related to minimum winter temperatures in the regions of origin, with landraces from coastal regions showing the highest sensitivity. Fertilizer did not significantly affect foliar damage. In simulation studies based on observed foliar damage rates at Tel Hadya due to Mar. frosts, foliar damage alone did not decrease grain yield but decreased straw yield. Additional floret damage decreased grain yield and increased straw yield.

Durum wheat landraces from Syria

Syrian durum wheat landraces from diverse collection sites were evaluated for agronomic performance under arid conditions over two seasons at four locations, at two levels of nutrient availability.

Assessment of glutenin and phenotypic diversity of Syrian durum wheat landraces in relation to their geographical origin

Glutenin and phenotypic diversity within Syrian landraces composed of Triticum turgidu var. durum and T. aestivum was compared and related to some geographical and climatological characteristics.

Durum wheat landraces from syria. II. patterns of variation

Phenotypic variation components were estimated with respect to days to heading, flag leaf length and width, plant height, awn and spike length, awn and spike colour, spikelets per spike and seed shrivelling of 84 Syrian durum wheat landrace populations. Multivariate patterns of variation were established through principal component analysis to describe relationships between landrace groups and regions of collection. Agroecological site characteristics and plant traits were compared with respect to patterns of geographical variation. Grouping on the basis of landrace groups proved more discriminative than on the basis of regions of origin. Landraces originating from sites characterized by favourable growth conditions tended to be later in heading and to have longer spikes with longer awns but with less spikelets. The observed relation between favourable growth conditions in the regions of origin and smaller flag leaves may be caused by genotype × environment interaction.

Durum wheat landraces from Syria. I. Agro-ecological and morphological characterization

A total of 185 durum wheat (Triticum turgidum var. durum Desf.) landraces was collected from 166 sites in the Syrian Arab Republic. With K-means clustering the collecting sites are grouped based on four climatological variables to create relatively homogeneous regions of origin with respect to agro-ecological characteristics. Stepwise Discriminant Analysis confirmed the minimization of variation within regions.

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

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.