Abstract: Irrigation is the most important factor in determining bread wheat (Triticum aestivum L.) yield in Egypt. The effects of different water regimes were investigated during two years on growth and yield components of the cultivar Gemmeiza 9 cultivated under three and four irrigations at 30 days interval, and five and six irrigations at 25 days interval. Grain filling rate and effective grain filling period were also calculated for each treatment. Significant effects of the water regime were found on all measured traits. However, increasing the number of irrigations from five to six, keeping the same interval of time between irrigations, did not significantly increased grain yield, harvest index, number of tillers and spikes per m2, spike length and fertility, thousand kernel weight and grain weight per spike. The grain production obtained by irrigation (or irrigation efficiency) was similar under three and four irrigations at 30 days interval but drastically decreased under five and six irrigations at 25 days interval. For the number of tillers and spikes per m2 as well as for grain yield, gains decreased with each additional irrigation, up to three irrigations. Conversely, for the number of grain per spike and to a lesser extent for thousand kernel weight, the highest gains were noted when both the number and frequency of irrigation increased, i.e. when the crop was irrigated five times at 25 days interval, rather than four times at 30 days intervals. The study emphasizes the importance, for irrigated wheat, to define irrigation timing and frequency that allow maximal yield and optimal use of irrigation water.
Abstract: Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C3 crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency for grain and biomass production (WUEG and WUEB, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as within bread wheat. It was also positively correlated to stomatal density. The highest WUEG and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUEB and biomass than durum wheat. WUEG and WUEB were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUEG was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUEG. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships between WUEG and its different components (water consumed, transpiration efficiency and carbon partitioning).
Abstract: The present study was aimed to examine different agronomic traits in 100 safflower genotypes. The experimental design was a 10 x 10 simple lattice. The results of analysis of variance demonstrated that the differences among genotypes were highly significant (P<0.01) for all studied traits. Phenotypic and genotypic correlations showed that the grain yield per plant is significantly correlated with grain yield per plot, biomass, number of capitula, 100 seed weight, number of secondary branches, and oil yield per plant. There was also a positive correlation between kernel% and oil content, therefore selection for high oil content can be based on thin-hull seeds. High values of phenotypic and genotypic coefficients of variation were obtained for most traits, indicating high variability in the traits under study. Phenotypic coefficients of variation (PCV) ranged from 3.3% in days to maturity to 42% in ineffective capitula and genotypic coefficients of variation (GCV) ranged from 3.65% in days to bud formation to 35.7% in oil yield. The recorded data were subjected to principal component analysis. The results showed that seven principal components with eigen values more than one explained 80.7% of the total variability. The genotypes were classified in four groups: A, B, C and D for safflower breeding goals (high grain and oil yield, short growth duration) based on PC1 and PC2 (as the most important principal components).
Abstract: The relationship between carbon isotope discrimination (Δ), grain yield, and water use efficiency for biomass (WUEB) and grain yield (WUEG) were analyzed in a set of bread wheat (Triticum aestivum L. subsp. aestivum) genotypes including seven landraces as well as the Iranian cultivar Zakros. No significant relationship was found between Δ and grain yield. A significant negative correlation was noted between Δ, WUEG and WUEB. The Iranian landraces and the modern cultivar Zakros mainly differed for grain yield, harvest index and WUEG. These results indicate that under well-watered conditions, Δ does not represent an accurate secondary trait for yield but can be used to estimate water use efficiency. They also suggest that WUEG under well-watered conditions has been improved by modern selection through an increase of harvest index rather than of transpiration efficiency.
Abstract: Wheat crops growing in arid and semi-arid regions generally experience some kinds of water-deficit. Water managing in the crop is partly depended on the stomatal characteristics. Therefore, reliable selection and breeding for suitable stomatal characteristics is of a great importance where water supplies are limited. This study was aimed to investigate different characteristics of stomata in Iranian wheat land races and wheat wild relatives not being studied so far. The results revealed that a huge variation exist between wheat land races and wheat wild relatives and even within the land races and wild relatives for different aspects of stomatal characteristics. Significant differences were found among the accessions of same ploidy level on the both adaxial and abaxial surfaces of flag leaf for stomatal frequency. Variation within diploid accessions was much higher than variation within either tetraploid or hexaploid wheats. The mean of stomatal frequency was the highest in diploids, intermediate in tetraploid and the least in hexaploids. Conversely, stomatal length and width was the lowest in diploids and highest in hexaploids indicating a negative relationship between stomatal frequency and stomatal size. Variations for stomatal area per unit leaf area were also found among and within ploidy levels. Nonetheless a particular trend was not found as the ploidy level changed. In general, this study revealed that wild species of wheat and landraces indicated variation for different aspects of stomatal characteristics and therefore they can be used in wheat breeding programs aiming to manipulate water-transpiration in wheat.
Abstract: Wheat is one of the most important crops in the world. Its study has involved anatomy, ecology, physiology, molecular biology, biotechnology and cultivation. Knowledge of the relationship of diploid, tetraploid and hexaploid wheat with stomatal characteristics and water-use efficiency is spare and is subject to argument. The present study was aimed to examine different characteristics of stomata in 28 Iranian landraces belonging to the species T. monococcum L. subsp. monococcum (2n = 2x =14), T. turgidum L. subsp. durum (Desf.) Husn. (2n = 4x = 28) and T. aestivum subsp. aestivum (2n = 6x = 42), respectively and investigated a possible relationship between these characteristics and water use efficiency by pot cultivation experiments. The results revealed large variation among landraces as well as between the different species for stomatal frequency and size. The diploid wheat species had the highest stomatal frequency and the lowest stomatal length and width. The hexaploid species had a lower stomatal frequency than the tetraploid species. A highly significant relationship was noted between the value of those traits on the adaxial and abaxial surfaces of the leaf. The ratio of adaxial to abaxial values appeared to be constant for a given species. Both stomatal frequency and size were associated with ploidy level, but also with the nature of the constituting genomes of the species. A highly significant negative association was found among accessions between stomatal frequency and size. As a consequence, the variation for stomatal area per unit leaf area was less than for the other traits. Diploid and hexaploid wheat have significantly higher water use efficiency, compared to tetraploid wheat. No clear association was found, however, between water use efficiency and stomatal characteristics
