Nitrogen deficiency tolerance and responsiveness of durum wheat genotypes in Ethiopia

Development of low-nitrogen (N) tolerant and N-responsive durum wheat genotypes is required since nitrogen efficiency has emerged as a highly desirable trait from economic and environmental perspectives. Two hundred durum wheat genotypes were evaluated at three locations under optimum (ON) and low (LN) nitrogen conditions to screen genotypes for low-nitrogen tolerance and responsiveness to an optimum N supply. The results showed significant variations among the durum wheat genotypes for low-N tolerance and responsiveness. The average reduction in grain yield under the LN condition was 48.03% across genotypes. Only 17% of the genotypes tested performed well (grain yield reduction <40%) under LN conditions. Based on the absolute grain yield, biomass yield, and normalized difference vegetative index value, on average, 32, 14, 17, and 37% of the tested genotypes were classified as efficient and responsive, efficient and nonresponsive, inefficient and responsive, and inefficient and nonresponsive, respectively. Considering the absolute and relative grain yield, biomass yield, normalized difference vegetative index values, and stress tolerance indices as selection criteria, 17 genotypes were chosen for subsequent breeding. Among the screening indices, geometric mean productivity, stress tolerance index, yield index, and stress susceptibility index exhibited positive and significant correlations with grain yield under both N conditions; hence, either of these traits can be used to select low-N-tolerant genotypes. The common genotypes identified as LN-tolerant and responsive to N application in this study could be used as parental donors for developing N-efficient and responsive durum wheat varieties

Temperature, planting depth, and genotype effects on seedling characteristics and seeding rate effects on agronomic and quality performance of winter wheat (Triticum aestivum L.)

Temperature levels, planting depths, and cultivars, affected seedling traits as expected. An increase in temperature from 12.8/12.8 to 20/20°C increased coleoptile length by 21 min implying that higher temperatures facilitated coleoptile elongation. An increase in planting depth from 2.5 to 7.5 an increased coleoptile length, shoot length, and fresh weight and decreased root length and germination % of the seedlings across cultivars. Cultivars had a wide range of responses in their mean performance for the seedling traits. Scout 66, Nekota, and Niobrara were considered to have good seedling vigor while Alliance, Arapahoe and Centura, were considered to have poor seedling vigor. Strong and significant positive correlation between coleoptile length and germination %, shoot length and fresh weight, and fresh weight and dry weight were observed. In summary, planting depths and cultivars had a greater impact on seedling traits than did our temperature levels. Planting depth and cultivars are controllable management factors; hence the optimum depth must be practiced for the appropriate cultivar. Coleoptile length is the trait that was most significantly affected by temperature regimes, planting depths and cultivars. It is the best predictor of seedling vigor and hence can be used as a selection criterion in the development of cultivars with vigorous seedlings. While numerous experiments have studied how seeding rates affect agronomic performance of wheat (Triticum aestivum L.) cultivars, there are no or very few experiments which have studied how seeding rates affect end use quality particularly of modern wheat cultivars. Twenty winter wheat cultivars, were evaluated to assess the effect of cultivar and seeding rate on agronomic and quality performance of wheat. Significant differences among environments, seeding rates, cultivars and some of their interactions were identified. Lower seeding rates decreased stand density, grain yield and thousand-kernel weight and caused later flowering. Lower seeding rates also lowered flour yield and mixing time and raised flour protein content and mixing tolerance. Cultivars responded more to environmental conditions than to seeding rates. Agronomic and end use quality traits are greatly influenced by the prevailing environmental conditions, but not as much by seeding rates. Seeding rate is a predictable environmental factor which affects some agronomic and end use quality traits of wheat, hence should be carefully studied to obtain higher grain yields with relatively better end use quality

Low Nitrogen Narrows down Phenotypic Diversity in Durum Wheat

AbstractBreeding for nitrogen use efficiency has become the major global concern and priority to improve agricultural sustainability. In an attempt to quantify genetic variation and identify traits for optimum and low N environments, 200 durum wheat genotypes were evaluated at three locations in the central highlands of Ethiopia during the 2020 growing season. The experiments were arranged in alpha lattice design with two replications. The results revealed significant differences among genotypes for all studied traits under both N conditions, indicating ample opportunities for genetic improvement. All traits except days to heading and maturity, grain filling period and grain protein content were higher under optimum than under low N. High values of genotypic and phenotypic coefficients of variations, broad sense heritability and genetic advance as percent of the mean were observed for number of fertile tillers and number of seed per spike (NSPS) under optimum, and spike length and NSPS under low N conditions. Cluster analysis classified the durum wheat genotypes into thirteen and eight clusters under optimum and low N, respectively. Principal component analysis detected five and four components which explained 81.29% and 73.63% of the total variations under optimum and N stress conditions, respectively. The present study confirmed the existence of wide genetic variability among the durum wheat genotypes under optimum and low N conditions; and low N lowers the level of diversity. Thus, our study paves the possibility for improvement of durum wheat genotypes through selection and hybridization for increased grain yield and adaptation to N stressed conditions

Nitrogen Deficiency Tolerance and Responsiveness of Durum Wheat Genotypes in Ethiopia

Development of low-nitrogen (N) tolerant and N-responsive durum wheat genotypes is required since nitrogen efficiency has emerged as a highly desirable trait from economic and environmental perspectives. Two hundred durum wheat genotypes were evaluated at three locations under optimum (ON) and low (LN) nitrogen conditions to screen genotypes for low-nitrogen tolerance and responsiveness to an optimum N supply. The results showed significant variations among the durum wheat genotypes for low-N tolerance and responsiveness. The average reduction in grain yield under the LN condition was 48.03% across genotypes. Only 17% of the genotypes tested performed well (grain yield reduction <40%) under LN conditions. Based on the absolute grain yield, biomass yield, and normalized difference vegetative index value, on average, 32, 14, 17, and 37% of the tested genotypes were classified as efficient and responsive, efficient and nonresponsive, inefficient and responsive, and inefficient and nonresponsive, respectively. Considering the absolute and relative grain yield, biomass yield, normalized difference vegetative index values, and stress tolerance indices as selection criteria, 17 genotypes were chosen for subsequent breeding. Among the screening indices, geometric mean productivity, stress tolerance index, yield index, and stress susceptibility index exhibited positive and significant correlations with grain yield under both N conditions; hence, either of these traits can be used to select low-N-tolerant genotypes. The common genotypes identified as LN-tolerant and responsive to N application in this study could be used as parental donors for developing N-efficient and responsive durum wheat varieties

Evaluation of seedling characteristics of wheat (triticum aestivum L.) through canonical correlation analysis

To examine the seedling characteristics of nine different bread wheat (Triticum aestivum L.) varieties, several variables regarding seedling size and germination characteristics were analyzed using canonical correlation analysis. Significantly correlated first canonical variate pairs indicated that the variables within each set such as coleoptile length, shoot length and fresh weight within size set, and emergence rate index and germination percentage can be regarded as main factors for vigorous wheat seedlings. The variables such as root number, root weight and dry weight did not seem to have predictive power on seedling size measurements of wheat. Both emergence rate index and somewhat germination percentage within the first canonical variate of germination set appeared to be the correct factors for vigorous germination of wheat seed. Our analysis revealed that compared to other variables, coleoptile length and emergence rate index are powerful determinants of reliable germination, in turn better wheat stand establishment. Selecting for these traits in early generation is expected to increase the seedling vigor of wheat. Canonical correlation analysis was shown to be suitably sensitive to detect relationships between seedling variables in bread wheat

Nitrogen use efficiency and genotype-by-environment interaction in durum wheat genotypes under varying nitrogen supply

Nitrogen (N) use efficiency is important for wheat grain yield and quality. This study evaluated6 durum wheat genotypes in Ethiopia to determine the extent of nitrogen use efficiency (NUE) components and genotype-by-environment interactions under high and low N supply. The results showed that there was significant variation among the genotypes in grain yield and NUE components. Grain yield ranged from 3.30 to 6.22 t ha−1 under high N and 2.30 to 3.78 t ha−1 under low N conditions with an average reduction of 40.1%. Nitrogen harvest index, Nitrogen uptake efficiency (NUpE), Nitrogen utilization efficiency (NUtE) and NUE increased under low N compared to high N. NUtE varied from 28.6 to 43.9 kg kg−1 under high N and 39.5 to 51.2 kg kg−1 under low N while NUE increased from 26.4 under high N to 31.8 kg kg−1 under low N. Grain yield showed significant and positive associations with most of NUE components under both N conditions. NUpE and NUtE are the two important traits that contribute to NUE. N-efficient genotypes were found to be the most stable genotypes. Thus, the study emphasizes the importance of selecting genotypes with improved grain yield and NUE traits under low N conditions.</p

Evaluation of seedling characteristics of wheat ( Triticum aestivum L.) through canonical correlation analysis

To examine the seedling characteristics of nine different bread wheat ( Triticum aestivum L.) varieties, several variables regarding seedling size and germination characteristics were analyzed using canonical correlation analysis. Significantly correlated first canonical variate pairs indicated that the variables within each set such as coleoptile length, shoot length and fresh weight within the size set, and emergence rate index and germination percentage can be regarded as main factors for vigorous wheat seedlings. The variables such as root number, root weight and dry weight did not seem to have predictive power on seedling size measurements of wheat. Both emergence rate index and somewhat germination percentage within the first canonical variate of germination set appeared to be the correct factors for vigorous germination of wheat seed. Our analysis revealed that compared to other variables, coleoptile length and emergence rate index are powerful determinants of reliable germination, and in turn for better wheat stand establishment. Selecting for these traits in early generation is expected to increase the seedling vigor of wheat. Canonical correlation analysis was shown to be suitably sensitive to detect relationships between seedling variables in bread wheat