Contribution of Agro-Physiological and Morpho-Anatomical Traits to Grain Yield of Wheat Genotypes under Post-Anthesis Stress Induced by Defoliation

Post-anthesis drought affects wheat production worldwide, primarily through the limitation of grain filling. The enhanced remobilization of stem reserves induced by drought can provide considerable carbon sources for grain filling. The aim of this study, which was part of an ongoing wheat-breeding program targeting drought tolerance, was to assess the ability of 20 contrasting common wheat genotypes (2 cultivars, 8 F6:7 families (FAM), and 10 parent genotypes (PAR) used to make the families) to remobilize stem dry matter under water-stressed conditions simulated via defoliation 10 days after anthesis, and to estimate the contribution of stem dry matter remobilization to grain weight. In two-year field trials, the genotypes were scored for agro-physiological and peduncle morpho-anatomical traits. Stem reserve contribution to grain weight per spike was significantly enhanced in defoliated plants but did not differ amongst the groups of genotypes. F6:7 families had higher grain-filling rate and 1000-grain weight but without improvement in grain weight per spike under defoliation compared with parental groups. The total area of chlorenchyma, phloem-area-related traits, and stem reserve contribution to grain weight were positively associated with grain weight per spike under defoliation, whilst in both treatments, the grain-filling rate was determined by stem height. These results imply that the grain-filling rate is a trait desirable for drought tolerance that can be improved during the breeding process. © 2023 by the authors