Mechanism of pod dehiscence in legumes: insights from phenotypic, anatomical, physiological and molecular studies.

Pod shattering describes the sudden splitting of dried mature legume pods to eject seeds via mechanical tension. Though vital for wild legume reproduction, it severely hinders crop harvesting and causes heavy yield losses, making it an unfavorable trait for cultivation. Pod shattering exists in legumes, grasses and brassicas, yet it is most prominent in legumes and a primary focus of crop domestication and breeding. This review analyzes the mechanism of pod shattering in legumes from the perspectives of morphology, anatomy of the pod suture zone, pod valve physiology, and molecular biology, with the aim of providing references for exploring practical strategies to alleviate pod shattering and for breeding cultivars resistant to pod shattering. The relationship between morphology and pod shattering in legumes varies substantially among different varieties, whereas the twisting phenomenon in common bean with longer pods deserves attention. Pod shattering in legumes mainly takes place at the pod ventral suture, modulated by soybean ventral fibrous cap cells, common bean valve margin cells and mesocarp lignification. Endogenous hormones in the pod suture stimulate hydrolases to degrade cell walls within the dehiscence zone and trigger shattering, while susceptible pods exhibit more pronounced fibrosis and lignification. Many legume pod-shattering genes such as Pdh1, SHAT1-5, GmMYB26, PvPdh1 and PvMYB26 have been widely studied. To clarify pod shattering mechanisms, we need to combine genetic improvement, plant structure adjustment and field management. Future work should integrate structural and physiological analyses of dehiscence zones to discover more shattering-related genes and develop practical field mitigation strategies, supporting the domestication and breeding of shatter-resistant legumes.