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Increasing biomass allocation to the root system may increase soil-organic carbon stocks and confer drought adaptation in water-limited environments. Understanding the genetic bases and inheritance of biomass allocation is fundamental for drought tolerance breeding and soil health. The objective of this study was to determine the general and specific combining ability, maternal effects and the mode of gene action controlling the major yield and biomass allocation related traits in wheat to identify good combiners for breeding and enhanced carbon sequestration. Ten selected wheat genotypes were crossed in a full diallel mating design, and 90 F2 families were generated and evaluated in the field and greenhouse under drought-stressed and non-stressed conditions. Significant differences were recorded among the tested families revealing substantial variation for plant height (PH), kernels per spike (KPS), root biomass (RB), shoot biomass (SB), total plant biomass (PB) and grain yield (GY). Additive gene effects conditioned PH, SB, PB and GY under drought, suggesting the polygenic inheritance for drought tolerance. Strong maternal and reciprocal genetic effects were recorded for RB across the testing sites under drought-stressed conditions. Line BW162 had high yield and biomass production and can be used to transfer favourable genes to its progeny. The parental line LM75 maintained the general combining ability (GCA) effects in a positive and desirable direction for SB, PB and GY. Early generation selection using PH, SB, PB and GY will improve drought tolerance by exploiting additive gene action under drought conditions. Higher RB production may be maintained by a positive selection of male and female parents to capture the significant maternal and reciprocal effects found in this study. [ABSTRACT FROM AUTHOR]

Genetic diversity is invaluable in developing climate-smart and drought-adapted wheat varieties. The aim of this study was to determine the extent of genetic variation present in wheat germplasm collections for biomass allocation and drought tolerance based on complementary phenotypic and root attributes and high-density single nucleotide polymorphism (SNP) markers to select breeding parents. A total of 97 bread wheat (Triticum aestivum L.) genotypes were evaluated in field and greenhouse trials under drought-stressed and non-stressed conditions. The molecular variance analysis showed that the intrapopulation variance was very high at 99%, with a small minimal inter-population variance (1%). The genetic distance, polymorphic information content and expected heterozygosity were 0.20–0.88, 0.24–1.00 and 0.29–0.58, respectively. The cluster analysis based on SNP data showed that 44% and 28% of the assessed genotypes maintained their genetic groups when compared to hierarchical clusters under drought-stressed and non-stressed phenotypic data, respectively. The joint analysis using genotypic and phenotypic data resolved three heterotic groups and allowed the selection of genotypes BW140, BW152, BW157, BW162, LM30, LM47, LM48, LM52, LM54 and LM70. The selected genotypes were the most genetically divergent with high root biomass and grain yield and are recommended for production or breeding. [ABSTRACT FROM AUTHOR]

Combining ability effects for yield related traits can serve as selection criteria to pursue breeding for optimal biomass allocation in wheat (Triticum aestivum). The objective of this paper is to provide information based on a retrospective quantitative genetic analysis on combining ability studies of wheat for yield and yield‐related traits to predict potential genetic gains achievable in improving biomass allocation for drought tolerance and soil carbon storage. The study compares data on the general combining ability and specific combining ability effects of wheat for yield and related traits under optimum and drought stressed conditions from 40 studies around the world. Days to heading (DTH), plant height (PH), number of tillers per plant (TN), kernels per spike (KPS), 1,000‐kernel weight (TKW), shoot biomass (SB), and grain yield (GY) exhibited wide variation for general combining ability (GCA) and specific combining ability effects. Progeny performance increased by 14.30 and 4.04% for SB and GY, respectively, compared with parental values under optimum water conditions. Number of tillers and SB exhibited positive associations with GY (.45 ≤ r ≤.85, p <.05) under both water conditions. Meta effect sizes for drought stress were negative. The highest meta‐effect sizes were calculated for DTH (−4.5) followed by SB (−2.0), whereas KPS (−1.25) had the lowest. The genetic gains for PH, SB, and other yield components showed that divergent crosses involving complementary parents could enhance biomass allocation patterns in wheat. This could be used as a basis for improving biomass allocation to roots. Core Ideas: There is sufficient genetic variation in wheat genotypes for manipulating biomass allocation.The number of kernels per spike is stable under varying moisture conditions.Shoot biomass and grain yield expression are severely confounded by drought.Aboveground traits are important for indirect selection of root traits. [ABSTRACT FROM AUTHOR]

Field assessments of crop water use efficiency (WUE) are resource‐consuming since they require simultaneous assessment of the total amount of water assimilated by crops for biomass and/or grain production. Alternative methods exist, such as estimating the carbon isotopic ratio (13C/12C) of the crop's leaf, aboveground biomass, or grain samples. There is limited information on the determinants of the accuracy of carbon isotopes in estimating water use efficiency between crop types and environments. Therefore, this study aimed to evaluate the extent to which the estimation of the 13C/12C ratio in crop parts constitutes an accurate proxy of WUE, globally. Data on observed WUE (WUEobs) were collated involving 518 experiments conducted worldwide on major cereals and legumes and compared with WUE estimates (WUEest) from carbon isotopes. The mean WUEobs among all experiments was 3.4 g L−1 and the mean absolute error (MAE) was 0.5 g L−1 or 14.7% of WUEobs, corresponding to accurate predictions at p < 0.05. However, the percentage mean absolute error of observed water use efficiency (%MAE) estimated from grains was 3.6 ± 11.5%, which was lower than the %MAE from aboveground biomass collected at harvest (3 ± 22.8%). In addition, the %MAE increased from 1.1 ± 5.1% for soybean, 1.6 ± 7.2% for maize, 1.2 ± 8.6% for rice, 1.8 ± 12.1% for groundnut, 2.1 ± 14.3% for cowpea, 2.3 ± 16.2% for bush bean, 1.8 ± 19.9% for wheat, 2.2 ± 21.4% for barley to 6.3 ± 39.3% for oat, with only the latter corresponding to significant errors. WUEest were, in all cases, unbiased but slightly overestimated from 0.8% (maize) to 15.4% (oat). The accuracy in estimating WUE significantly decreased with the increase in soil clay content, with sand, showing a positive correlation of 0.3 with %MAE, but negatively correlated with the silt content (r = −0.4). Furthermore, a multivariate analysis pointed out a tendency for prediction errors and bias to increase with the decrease in WUEobs and air temperature. Using carbon isotopes for estimating crop WUE thus appeared reliable for all crops and world environments, provided grain samples are considered. The technique tended to perform better under high WUE conditions, such as those generally found in maize and soybean cropping systems. The identified factors that affect the accuracy of using carbon isotopes in measuring WUE provide valuable insights for water resource management and sustainable crop production. These findings contribute to the ongoing discourse on water conservation strategies in agriculture, offering a basis for decision‐making in crop improvement programs. Implementing the recommended practices from this study can potentially improve yield gains and promote resilient and sustainable agricultural systems in the changing environmental circumstances. Further research should investigate the mechanisms that cause low accuracy of the isotopic technique using aboveground biomass and under arid and cool environments. [ABSTRACT FROM AUTHOR]