Epistasis and genotype-by-environment interaction of grain protein content in durum wheat

Dissecting Genotype by Environment Interactions in Moroccan Wheat: An Advanced Biplot and Heatmap Analysis Unveiling Agronomic, Quality Traits, and Genotypic Stability for Tailored Breeding Strategies

This five-year study (2016-2021) across diverse Moroccan agro-climatic zones investigated genotype by environment (G × E) interactions in wheat, focusing on variations in agronomic traits and quality attributes such as protein and gluten content. Significant environmental effects were observed on key traits, like yield, thousand kernel weight (TKW), and spikes per square meter (Spk/m2), highlighting environmental factors' role in wheat yield variability. In the Tassaout (TST) location, notable genotypic effects emerged for traits like biomass, underscoring genetic factors' importance in specific contexts, while in Sidi El Aidi (SEA) and Marchouch (MCH), genotypic effects on yield and its components were predominantly absent, indicating a more substantial environmental influence. These findings illustrate the complexity of G × E interactions and the need for breeding strategies considering genetic potential and environmental adaptability, especially given the trade-offs between yield enhancement and quality maintenance. Insights from the biplot and heatmap analyses enhanced the understanding of genotypes' dynamic interactions with environmental factors, establishing a basis for strategic genotype selection and management to optimize wheat yield and quality. This research contributes to sustainable wheat breeding in Morocco, aligning with global efforts to adapt wheat breeding strategies to changing climatic conditions.

SSR markers and seed quality traits revealed genetic diversity in durum wheat (Triticum durum Desf.)

Genetic diversity and differences among durum-wheat cultivars evolved in various regions of the world are important for sustainable production in the current climate change scenario. Information regarding genetic differences was also important for the correct choice of parental material for the selection of high quality cultivars. Two elite and six obsolete cultivars of durum-wheat were characterized with 25-simple sequence repeats (SSR) markers. All accessions were evaluated for 2-agronomic-traits (Yield (Y) and Thousand-Kernel-Weight (TKW)) and 11 grain quality-traits (grain protein content (GPC), grain moisture contents (H), carotene content (CT), sedimentation test (SDS), gluten content (GC), gluten index (GI), semolina color index (L*, a*, b*) and alveographic parameters (W and P/L)) under randomized complete block design with three replication for two crop seasons (2015-2017). Genetic characterization through SSR markers revealed 126 alleles with an average of 5.04 alleles locus-1 and had average 0.79 polymorphism information content (PIC). The comparisons revealed that elite accessions were more productive in terms of grain yield and TKW, whereas obsolete accessions showed high GPC and end-use quality-traits. The generated dendrogram based on SSR markers, agronomic, seed quality-traits clearly differentiate the genotypes in two main groups obsolete and elite accessions. Analysis of correlation revealed a significant association between the traits TKW, Y, b*, a*, GPC, GC, SDS and H. High genetic diversity found between elite and obsolete cultivars for parameters such as yield, end-use quality and their correlation with SSR markers could help breeders for an eventual breeding program on durum-wheat.

Effects of Heat Stress on Growth, Physiology of Plants, Yield and Grain Quality of Different Spring Wheat (Triticum aestivum L.) Genotypes

Heat stress is one of the major threats to wheat production in many wheat-growing areas of the world as it causes severe yield loss at the reproductive stage. In the current study, 28 crosses were developed using 11 parental lines, including 7 female lines and 4 male testers following line × tester matting design in 2018–2019. Twenty-eight crosses along with their 11 parental lines were sown in a randomized complete block design in triplicate under optimal and heat stress conditions. Fifteen different morpho-physiological and grain quality parameters were recorded at different growth stages. Analysis of variance illustrated the presence of highly significant differences among wheat genotypes for all traits under both optimal and heat stress conditions. The results of combining ability unveiled the predominant role of non-additive gene action in the inheritance of almost all the studied traits under both conditions. Among parents, 3 parental lines WL-27, WT-39, and WL-57 showed good combining ability under both normal and heat stress conditions. Among crosses, WL-8 × WT-17, WL-37 × WT-17, WL-7 × WT-39, and WL-37 × WT-39 portrayed the highest specific combining ability effects for grain yield and its related traits under optimal as well as heat stress conditions. Biplot and cluster analysis confirmed the results of general and specific combining ability by showing that these wheat crosses belonged to a highly productive and heat tolerant cluster. Correlation analysis revealed a significantly positive correlation of grain yield with net photosynthetic rate, thousand-grain rate, and the number of grains per spike. The designated parental lines and their crosses were selected for future breeding programs in the development of heat resilient, climate-smart wheat genotypes.

The use of weighted multiple linear regression to estimate QTL-by-QTL epistatic effects

Knowledge of the nature and magnitude of gene effects, as well as their contribution to the control of metric traits, is important in formulating efficient breeding programs for the improvement of plant genetics. Information concerning a genetic parameter such as the additive-by-additive epistatic effect can be useful in traditional breeding. This report describes the results obtained by applying weighted multiple linear regression to estimate the parameter connected with an additive-by-additive epistatic interaction. Three weight variants were used: (1) standard weights based on estimated variances, (2) different weights for minimal, maximal and other lines, and (3) different weights for extreme and other lines. The approach described here combines two methods of estimation, one based on phenotypic observations and the other using molecular marker data. The comparison was done using Monte Carlo simulations. The results show that the application of weighted regression to the marker data yielded estimates similar to those obtained by phenotypic methods.

Yield vs. quality trade-offs for wheat in response to carbon dioxide and ozone

Although it is established that there exist potential trade-offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO₂ ) and ozone (O₃ ), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO₂ and O₃ , we analysed 57 experiments with CO₂ or O₃ exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O₃ was associated with a change in grain protein yield of 8.1% (R² =0.96), while a change in yield effect of 10% by CO₂ was linked to a change in grain protein yield effect of 7.5% (R² =0.74). Superimposed on this effect, elevated CO₂ , but not O₃ , had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO₂ restricts grain protein accumulation, which is absent for O₃ . Grain mass, another quality trait, was more strongly affected by O₃ than grain number, while the opposite was true for CO₂ . Harvest index was strongly and negatively influenced by O₃ , but was unaffected by CO₂ . We conclude that yield vs. protein trade-offs for wheat in response to CO₂ and O₃ are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO₂ has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO₂ -induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade-offs are very different in wheat exposed to elevated O₃ compared to elevated CO₂ .