Origin of current intermediate wheatgrass germplasm being developed for Kernza grain production

Intermediate wheatgrass (IWG, Thinopyrum intermedium [Host] Barkworth D. R. Dewey) has been developed as a perennial grain crop for human consumption along with providing environmental benefits and ecosystem services. Grain and products derived from IWG cultivars improved for food production have been marketed under the registered trademark, Kernza. Development of IWG as a perennial grain crop began in 1980s with a phenotypic recurrent selection program as the Rodale Institute (RI) and the Big Flats Plant Material Center (BFPMC) used IWG plant introductions (PI) from the National Plant Germplasm System (NPGS) to improve populations of IWG. Initial selections were provided to The Land Institute (TLI) where they were subsequently improved for grain production, yet the identity of the founder material of improved, food-grade IWG has not been publicly documented. Recently recovered original documents have been used to reconstruct the early breeding program to identify the most likely 20 PIs that form the founders of modern food-grade IWG. Molecular data using genotyping-by-sequencing in current elite breeding material, and remnant seed and plant material from the initial RI selections have provided supporting evidence for the historical records. The genetic origin for food-grade IWG is focused between the Black Sea and Caspian Sea in the Stavropol region of Russia, with smaller contributions likely from collections as distant as Kazakhstan in the east to Turkey in the west. This work connects the flow of germplasm and utility of NPGS PIs to present day IWG grain cultivars being developed in multiple breeding programs around the world.