Agronomic and pod traits in relation to pod shattering in cultivated soybeans

Pod dehiscence orpod shattering from mature soybean (Glycine max L.) is one of the most outstanding disadvantages in domesticated cultivars. Pod shattering in relation to 16 quantitative traits and 3 qualitative traits among 140 cultivars of vegetable soybeans, grain soybeans and small-grain soybeans was evaluated over two years. We found the pod shattering percentage is positively correlated with the number of productive branches, pod width, pod length, pod area, 100-seed weight, 1-seeded-pod percentage, 2-seeded-pod percentage and seed protein content, but negatively correlated with the plant height, pod height at the bottom, number of nodes on the main stem, 3-seeded-pod percentage, 4-seeded-pod percentage and seed oil content. The pod shattering percentage in vegetable soybeans is remarkably high, reaching up to 93%, 7.8 times higher than that of grain soybeans. A schematic model of the characteristics for shatter-susceptible and shatter-resistant soybean cultivars is proposed. The pod shattering in vegetable soybeans is related to the “umbrella-shaped” architecture and pod size. It is suggested to select lines with more 2-seeded and 3-seeded pods for vegetable soybeans, but a higher seed oil content and greater node number on the main stem for grain soybeans and small-grain soybeans, to avoid pod shattering in future breeding programmes.