Bottom‐up redistribution of biomass optimizes energy allocation, water use and yield formation in dryland wheat improvement

Abstract

BACKGROUND Modern wheat cultivars have been developed having distinct advantages in many aspects under drought stress, such as plasticity in biomass allocation and root system architecture. A better understanding of the biomass allocation mechanisms that enable modern wheat to achieve higher yields and yield‐based water use efficiency (WUEg) is essential for implementing best management strategies and identifying phenotypic traits for cultivar improvement. We systematically investigated the biomass allocation, morphological and physiological characteristics of three ploidy wheat genotypes under 80% and 50% field water‐holding capacity (FC) conditions. Some crucial traits were also assessed in a complementary field experiment. RESULTS The diploid and tetraploid genotypes were found to allocate more biomass to the root system, especially roots in the topsoil under drought stress. Our data illustrated that lower WUEg and yield of these old genotypes were due to excessive investment in the root system, which was associated with severely restricted canopy development. Modern hexaploid genotypes were found to allocate smaller biomass to roots and larger biomass to shoots. This not only ensured the necessary water uptake, but also allowed the plant to distribute more assimilates and limited water to the shoots. Therefore, the hexaploid genotypes have evolved a stable plant canopy structure to optimize WUEg and grain yield. CONCLUSION This study demonstrated that the biomass shift from below ground to above ground or a more balanced root:shoot ratio tended to optimize water use and yield of the modern cultivars. This discovery provides potential guidance for future dryland wheat breeding and sustainable management strategies. © 2021 Her Majesty the Queen in Right of Canada Journal of The Science of Food and Agriculture © 2021 Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri‐Food Canada.

Improved Salinity Tolerance-Associated Variables Observed in EMS Mutagenized Wheat Lines

“…Osmotic stress often causes a deterioration of plant monovalent ion balance [ 40 ], but for OA10, no obvious ion imbalance was detected ( Figure 2 , Figure 3 , Figure 4 and Figure 5 ). Studies suggest that modern hexaploid wheat genotypes have shifted their biomass from below ground to above ground to optimize water use [ 41 ], however, this trait was not investigated as part of this study. Moreover, as ABA can prevent transpiration and thereby also decrease Na + movement from the root to the stem [ 42 ], it would be a feature to look for in future studies to understand better the patterns that appeared.…”

Distinctive root system adaptation of ploidy wheats to water stress: A cue to yield enhancement

“…Drought is considered the most severe abiotic stress affecting plant growth and limiting crop yield throughout the domestication process from primitive to modern hexaploid genotypes. Therefore, it is becoming more and more important to develop drought‐resistant varieties (Bruce et al, 2002; Kitchen et al, 1999; Li, Ma, Guo, et al, 2022).…”

“…However, some studies have shown that an overall increase in root biomass does not imply increased water uptake, which should be reduced in crop breeding (Zhang et al, 1999; Reynolds et al, 2006; Aziz et al, 2016). Reduced root mass may reduce root growth redundancy and facilitate redistribution, transferring more dry matter from roots to shoots (Siddique et al, 1990; Zhang et al, 1999; Song et al, 2009; Li, Ma, Guo, et al, 2022). The effect of reducing root size under drought conditions on wheat grain yield has been extensively investigated, but conclusions remain controversial.…”

“…Although root traits are typical features of drought resistance, it is important to elucidate their respective contributions to improving agronomic performance and obtaining more drought‐tolerance varieties. Most studies assessing drought‐resistance improvement programs have focused on above‐ground components (Wang et al, 2016; Li, Ma, Guo, et al, 2022). Plant genetic resources with large untapped root diversity may help develop drought‐resistant varieties (Fang et al, 2017; Nakhforoosh et al, 2021).…”

“…We previously showed that advances in drought resistant breeding shifted biomass from roots to aboveground components, a shift accompanied by changes in root systems and grain production (Li et al, 2016; Li, Ma, Guo, et al, 2022). Most studies on root traits and grain yield under drought conditions have focused on hexaploid wheat, ignoring attention to changes in root traits during the transition from primitive to modern wheat.…”