A Step Toward the Development of Perennial Wheat: Characterization of Flowering Genes in Perennial Wheatgrasses and their Relationship to Wheat

Perennial wheat has yet to be realized. If successfully developed, it would provide the basis for a second green revolution based around truly sustainable production practices. Perennial growth habit is the result of continued alternation between vegetative and reproductive growth. An understanding of the basic flowering pathway has been developed in a number of annual species, including wheat, but the genetic basis regulating this process in perennials is very limited. To develop perennial wheat breeding on a repeatable scale, a full understanding of perennial habit in grasses most closely related to wheat must be attained. To complete this, we have cloned and characterized key flowering-time genes VRN1, VRN2, VRN3, PPD1 and TFL1 in the forage grass species Thinopyrum elongatum and Th. ponticum (tall wheatgrass) based on sequence available in public databases from annual cereals. Surprisingly, coding sequences for flowering genes in wheatgrass were highly conserved with annual cereals. Non-coding regions were less conserved and may be important in the regulation of perennial habit. Results from the quantitative expression analysis of these five flowering genes in wheat and wheatgrass show that their expression, when existing knowledge of flowering pathways in wheat and perennial brassica species are considered, follow a somewhat predictable model and is related to the stage of the plant’s life cycle. This first step toward understanding the perennial growth habit in wheatgrass is critical for accelerating the development of perennial wheat and has the additional benefit of providing useful insights for perennial forage grass development.