Wildrice (Zizania L.) in North America: Genetic resources, conservation, and use

Abstract

Wildrice (Zizania spp.) is an annual aquatic grain, occurring naturally in shallow waters of lakes and streams. Zizania palustris is found mainly in the Great Lakes region of the USA and Canada. This species of wildrice has been harvested from natural stands for many centuries (and still is) by certain groups of Native Americans who consider it sacred. It has also been cultivated in paddies since 1950 and is still undergoing domestication as a crop. Two other species are present in North America: Z. aquatica and Z. texana. The former occurs throughout the Great Lakes, St. Lawrence Seaway, Atlantic Coast, and Gulf Coast regions. The latter is endangered, being present only in a small stretch of the San Marcos River in Texas, as well as in several refugia populations. Genetic studies suggest Z. palustris has a strong syntenic relationship to Oryza sativa. Genetic diversity varies widely among and within stands but is generally high, although inbreeding is higher than expected in certain populations. A recently identified potential threat is the toxic effects of sulfide in sediments under certain conditions. Major preservation concerns include declining or disappearing stands due to hydrology issues and shoreland development, difficulty storing seeds either short term or long term, and narrow stratification and seed moisture requirements to break dormancy. There are no accessions currently being conserved in the US National Plant Germplasm System. Development of ex situ storage protocols should continue while pursuing strategic preservation and restoration of natural stands, guided by knowledge of their population genetics.