ABSTRACT
Introduction: Wheat grain filling processes under post-anthesis stress scenarios depend mainly on stem traits and remobilization of stem water-soluble carbohydrates (WSC). Methods: A diverse panel of advanced semi-dwarf spring wheat lines, representing a natural variation in stem traits (WSC content, stem diameter, peduncle length, and stem wall width), was used to identify specific traits that reliably reflect the relationship between WSC and grain yield. The panel was phenotyped under various environmental conditions: well-watered, water-limited, and heat stress in Mexico, and terminal-drought in Israel. Results: Environmental stresses reduced grain yield (from 626 g m-2 under well-watered to 213 g m-2 under heat), lower internode diameter, and peduncle length. However, stem-WSC generally peaked 3-4 weeks after heading under all environmental conditions except heat (where it peaked earlier) and expressed the highest values under water-limited and terminal-drought environments. Increased investment in internode diameter and peduncle length was associated with a higher accumulation of stem WSC, which showed a positive association with yield and kernel weight. Across all environments, there were no apparent trade-offs between increased crop investment in internode diameter, peduncle length, and grain yield. Discussion: Our results showed that selecting for genotypes with higher resource investment in stem structural biomass, WSC accumulation, and remobilization could be a valuable strategy to ameliorate grain size reduction under stress without compromising grain yield potential. Furthermore, easy-to-measure proxies for WSC (stem diameter at specific internodes and length of the last internode, i.e., the peduncle) could significantly increase throughput, potentially at the breeding scale.
ABSTRACT
Autonomous seed dispersal is a critical trait for wild plants in natural ecosystems; however, for domesticated crop-plants it can lead to significant yield losses. While seed shattering was a major selection target during the initial domestication of many crops, this trait is still targeted in breeding programs, especially in 'orphan crops' such as sesame, whose capsules dehisce upon ripening. Here we used a mapping population derived from a cross between wild-type (dehiscent) × indehiscent lines to test the hypothesis that the selection against indehiscent alleles in sesame is a consequence of complex genetic interactions associated with yield reduction. We identified a major pleiotropic locus, SiKANADI1, associated with abnormal hyponastic leaf and indehiscent capsule, and genetically dissected its underlying mechanism using a set of near-isogenic lines. Transcriptional, anatomical and physiological information shed light, for the first time, on the polar regulatory gene network in sesame. The pleiotropic effect of SiKANADI1 on leaf and capsule structure and its influence on photosynthetic capacity and final yield are thoroughly characterized. Overall, our results provide new insights on the genetic and morphological mechanisms regulating capsule indehiscence in sesame, and discuss their evolutionary consequences and potential for future sesame breeding.