Patterns of dry matter production, allocation and water use in perennial wheat

Perennial crops offer the prospect of flexible, diversified and stabilized farming systems, by contributing grain and grazing while protecting environmental services. Recently, perennial wheat derivatives developed between bread wheat (Triticum aestivum L. [6n]) and perennial grass (e.g. Thinopyrum intermedium [6n]) have been reported to survive, regrow and contribute grain in the field at Cowra NSW, for up to four years. This PhD project examined the performance of four perennial wheat derivatives, relative to annual wheat and perennial grass, under controlled and field conditions, over three years. Three experiments addressed patterns of dry matter production and partitioning over growth cycles, how they changed under source or sink limitation, and patterns of root growth and water extraction under prolonged water deficit. Perennials developed greater dry matter in successive cycles, especially root dry matter, relative to annually replanted bread wheat, with perennial wheat derivatives intermediate between annual wheat and perennial grass. Perennials showed greater root growth and water extraction capacity at depth in prolonged drought, in controlled conditions and in the field. Perennial wheats differed in the extent of these parameters, but the most promising derivative approached or exceeded the perennial grass. These results added to previous reports, showing how perennial wheat could regrow in subsequent years, with increased root growth allowing greater access to soil water, especially at depth, in controlled conditions and the field. These results confirm the proof of concept of perennial wheat, and that research on perennial wheat should continue.