Variation in Seed Size in Soybean1

Abstract

AbstractSeed size (mass per seed) is an important yield component in soybean [Glycine max (L.) Merr.]; however, little is known of the variation in seed size within a seed lot. Consequently, the variation in seed size within seed lots collected from greenhouse and field experiments was investigated. Treatment variables included in the experiments were planting dates, cultivars (determinate and indeterminate), and source‐sink alterations applied during seed filling. Seed size distributions were determined using round‐hole screens ranging from 3.2 to 8.7 mm in diameter at intervals of 0.8 mm. All seed lots investigated exhibited a wide range in seed size from approximately 90 to greater than 200 mg seed−1. However, 40 to 80% of the seeds stayed on a single screen. The seed size of seeds on a single screen varied significantly among cultivars, planting dates, and years. Determinate cultivars tended to have a greater proportion of the seed on a single screen, but the range in seed size was similar to that exhibited by indeterminate cultivars. Treatments that altered mean seed size usually affected the proportions of the various sized seeds in the lot, more than the range in seed size. Variations in seed size within a seed lot were not associated with differences in seed density, specific seed coat mass, or seed N concentration. The data indicate that variation in mean seed size can be caused by variations in the proportion of the various sized seed in the seed lot, with relatively small changes in the range in seed size.