Mike,
Glad you broached the subject of seed size.

I recall a soybean breeder once telling me that there was an inverse relationship between seed size and yield. Simple as that.

He was a public breeder here in Ontario where a significant amount of our soybeans are exported into the high-end Asian markets. They are looking for large, clear hilum beans. One of the growers in the group was grousing a little that he was giving up too much yield growing for this market, and that the breeder should put some effort into yield.

The breeder then patiently explained that the highest yielding genetics - in general - come with a smaller inherent seed size, so selecting for large seed size was running counter to this trend. Exacerbate this challenge with then having to select only the clear hilum results of any cross ( I think clear hilum is a recessive trait), and the odds of a large seeded, clear hilum cultivar being a yield topper were very slim.

Any soybean crop we grow however, we need to try to maximize the seed size once the number of nodes, pods and seeds have been determined during the growing season...

Luke