Seed Storage: Recalcitrance, Dormancy, and Microbes

Successful seed storage is fundamental to plant breeding.  Each year diverse breeding lines and elite varieties need to be properly maintained for future use. Successful seed storage is also crucial for conserving the genetic diversity of plant species ex situ, which is especially important when global biodiversity is declining at ecosystem, species, and genetic levels.

Seed banks all over the world store seeds of thousands of plant species for this purpose. While seed banks store everything from agricultural crops to wild species, northern wild rice has never been successfully stored. This is in large part due to the very nature of the seed itself, its recalcitrant behavior. 

Seed Storage and Longevity source                                                                                   https://ecomyths.org/2015/05/26/myth-seeds-never-expire/             

Long-term Seed Storage

Wild rice seed can only remain viable in storage for one year in our program. This means that all of our breeding germplasm has to be grown out every year or else it would be lost. This takes up limited field space and valuable time. For conservation efforts, this also means that wild rice growing in our lakes and rivers is not preserved in seed banks for future seeding efforts or in case of a catastrophic environmental disaster. 

We have started long-term experiments to help us develop a better understanding of just how long various wild rice germplasm can survive in long-term storage. Every year for five years, we pull seed to test its viability.   

Dormancy

Wild rice enters a dormant state once the seed reaches maturity. Seed must be stored in low temperatures for 4-5 months to break dormancy. This slows the breeding process because winter nurseries are not possible. Dormancy is a complex physiological phenomenon involving physical barriers (seed coat impermeability), chemical barriers (growth inhibitors ie.e absiscic acid and lack of growth promoters), and necessary changes in the seed's physical state. We are currently focused on the chemical barriers to breaking dormancy in wild rice. 

http://www.seedbiology.de/hormones.asp

Microbes

Since wild rice seed cannot survive moisture contents below rougly 20%, the seed cannot be dried down and stored like other crops such as corn, wheat, or rice. As such, microbial growth is fairly commonplace in our seed storage. We are interested in what these microbes are, whether they affect wild rice germination rates, and if treating seed with antimicrobials can improve overall health of the seed. At the very least if we can reduce the stench that comes from all that microbe growth, we think everyone who has to work close to us may enjoy our company a bit more.