Effects of Early Harvest on Hard Seededness in Dry Bean

Effects of Early Harvest on Hard Seededness in Dry Bean

In the food industry, seeds which are used whole – like peas, dry beans, and soybeans – need to have a good hydration capacity, or the ability to absorb water, in order to be desired by consumers. Seeds that do not absorb water are called stone seeds / hard seeds and are considered a negative seed quality characteristic because they must be removed before processing. Cultivars that are known to have large amounts of stone seeds are seen as wasteful by canners and will be discounted in the marketplace.

Legumes are known to have both physical dormancy (PY) and physiological dormancy (PD) by the end of the seed’s development. Having a high PY is noted as the cause of stone seeds, but it is not known when or how it forms during development of the seed. It is theorized that PY develops either just before or just after seed physiological maturity and that PY decreases towards the end of the desiccation stage of bean seed development. In our initial studies, we observed physiological maturity in dry bean occurs approximately thirty-eight days after flowering. Harvesting around this approximate date should help us determine when the seeds begin to develop PY, and when PY begins to drop off while linking this to what the pods look like.

If hard seededness is related to the timing of harvest, it becomes more essential for producers to grow varieties that are not just less susceptible, but also varieties that mature at an appropriate time to ensure premature harvest – which leads to increased PY – does not occur.

There also exists an increased interest in black and navy beans for canning, and black beans are well known for producing stone seeds. Crosses have been done between the navy and black beans to increase the genetic variability in the navy germplasm, and this could potentially lead to an increase in stone seeds found in navy beans as well. Also, the analysis of bean seed biology regarding dormancy and the effects of after ripening of the seed would be useful to advance the rapid generation cycling (RGT) protocol for dry bean. By improving our understanding of seed biology and physiology, specifying the timing of developmental stages in bean, and linking the developmental times to morphological traits, we can improve bean seed quality and advance protocols for RGT.