Pod Shattering Tolerance in Brassica napus: Mechanisms, Genetic Regulation, Phenotyping and Breeding Strategies

Abstract

Brassica napus (oilseed rape/canola) is one of the world's most important oilseed crops, contributing significantly to global vegetable oil production, livestock feed, and industrial applications. However, pod shattering remains a major constraint to its productivity, causing substantial pre-harvest seed losses, reduced harvest efficiency, and economic losses under adverse environmental conditions. The increasing occurrence of climate-related stresses, including high temperature, drought, and strong winds, further exacerbates pod shattering, highlighting the urgent need for the development of shatter-resistant cultivars. This review comprehensively summarizes the current understanding of pod shattering tolerance in B. napus, focusing on its anatomical, physiological, biochemical, genetic, and molecular mechanisms. The structural organization of the silique, differentiation of the dehiscence zone, cell wall remodeling, lignification, and hormonal regulation are discussed as key determinants governing pod dehiscence. Recent advances in identifying major regulatory genes, including SHATTERPROOF (SHP), INDEHISCENT (IND), ALCATRAZ (ALC), FRUITFULL (FUL), and REPLUMLESS (RPL), together with quantitative trait loci (QTLs), have greatly improved the understanding of the genetic architecture underlying pod shattering resistance. The review also highlights conventional and high-throughput phenotyping approaches used to evaluate pod strength and seed retention, emphasizing the importance of standardized evaluation protocols for accurate selection. Furthermore, recent breeding strategies integrating conventional breeding, marker-assisted selection, genomic selection, speed breeding, and CRISPR/Cas-mediated genome editing are discussed as promising tools for accelerating the development of pod shattering-tolerant cultivars. Emerging multi-omics technologies, artificial intelligence-assisted phenotyping, and climate-smart breeding approaches are expected to further enhance breeding efficiency and genetic gain. Overall, integrating advanced molecular technologies with conventional breeding and robust phenotyping will facilitate the development of high-yielding, climate-resilient B. napus cultivars with improved pod shattering tolerance, thereby contributing to sustainable oilseed production, enhanced harvest efficiency, and global food security.