Effect of Node and Seed Position on Pod Thickness Related Indexes in Soybean

Pod thickness is a shape indicator in accordance with seed-filling process of soybean[Glycine max( L.) Merri. ].Four soybean lines with sub-indeterminate or determinate habit,different seed number of pods and similar growth period,including Jidou 12,Handou 5,Ludou 96150 and Qingxian 819-4,were served as materials. Thickness of tagged pods was measured continuously,and relationship between pod thickness and days after flowering was simulated with quadratic function to explore node effect and seed effect of seed-bulging related traits,including starting point,final point and duration of seed-bulging,maximum pod thickness and average rate of pod thickening. The results showed that,based on the effect sequence,sources of variation of tagged pod thickness were showed as inter-plant inter-node within plant,inter-pod within node inter-seed within pod. No difference of seed position effect was detected in 2-seeded pods,but significant difference of seed position effect in 3-seeded pods and 4-seeded pods,with seed position advantage sequencing by middle seed( s) distal seed seed near to pod stalk within a pod. The advantage seed was characterized as early seed bulging,higher seed-bulging rate and maximal pod thickness,as well as less potential of early termination of seed development. The seeds at both ends of the pod were apt to early terminate in the sub-indeterminate soybean lines. Those results will help to measure the pod thickness appropriately in the research of soybean seed-filling characteristics and extend the knowledge of position effect in soybean seed-filling traits.