Purdue University researchers have pinpointed the gene that controls whether soybean seed coats are hard or permeable. The findings, published in Nature Genetics, could be used to develop better varieties for southern and tropical regions, enrich the crop’s genetic diversity, and boost the nutritional value of soybeans.
The researchers found that a mutation in the gene GmHs1-1 causes the tough seed coats of wild soybeans to become permeable. Farmers selected that trait about 5,000 years ago in a key step to domesticating soybeans from their hard-seeded relative, Glycine soja. The gene could be modified to produce improved varieties for growing regions in which seed permeability can be a handicap. GmHs1-1 is also associated with the calcium content of soybeans, offering a genetic target for enhancing the nutrition of soy food products.
Understanding the mechanism that determines seed permeability could also give researchers better access to the largely untapped genetic diversity of wild soybeans to enrich cultivated varieties, whose lack of genetic richness has curbed improvements in yields.
“This is the first gene associated with hard seededness to be identified in any plant species,” said Jianxin Ma, associate professor of agronomy at Purdue. “This discovery could help us quickly pinpoint genes that control this trait in many other plants. We’re also excited about the potential applications for modifying the calcium concentration in seed coats. This could be transformative as we identify similar genes that control calcium levels in other legumes.”
Hard seededness enables the long-term survival of many wild plant species by protecting seeds in severe conditions and inhospitable environments, allowing them to remain dormant until conditions are right for germination. Encased in a water- and airtight coat, seeds can remain viable for extended periods of time, in some cases, more than 100 years. However, this hard skin prevents seeds from germinating quickly and in a uniform, predictable pattern. Wild soybean seeds take from several weeks to months to germinate whereas cultivated soybean seeds can begin absorbing water in 15 minutes.
The researchers’ next goal is to identify genes that interact with GmHs1-1 and understand how they work together to control calcium and possibly other mineral content.
