Responses of Forage Grass Seed Crops to Plant Growth Regulators in the Peace River Region of Canada

Peace river region of Canada is one of the globally reputed regions for the seed production of temperate forages and turf-grasses. Pre-mature lodging reduces seed productivity of those crops, owing to impairment of photosynthesis, pollination and seed development. Controlling plant heights by means of plant growth regulators (PGRs) has been a growing agronomic practice to tackle the lodging problem and thereby reducing yield loss. Those PGRs act on gibberellic acid biosynthetic pathway inhibiting cell elongation. Various study results show that the anti-gibberellic PGRs reduce plant height, lodging and yield losses. A number of field experiments with PGRs were conducted on creeping red fescue (Festuca rubra L. ssp. rubra Gaudin), meadow bromegrass (Bromus riparius Rehm) and timothy (Phleum pratense L.) seed crops at Beaverlodge Research Farm in the Peace Riven region. Three PGRs namely trinexapac-ethyl, chlormequat chloride and ethephon were applied at two-node (BBCH 31-32) and/or early heading (BBCH 51-52) growth stages. The forage seed crop species exhibited differential and weather-dependent responses to PGR application. F. rubra showed no measurable phenotypic response to PGRs. The responses of B. riparius and P. pratense were differentially pronounced in terms of reduction in plant height and lodging, and increase in seed yield in different growing seasons. The crops grown under relatively optimal soil fertility and moisture regimes showed more pronounced responses to PGR application in terms of reduction in plant heights, tolerance to lodging and increase in yield. Further studies are needed to understand how the PGRs interact with photosynthesis, respiration, and anti-oxidant activities under drought, cold and heat stress, which are the agro-ecological realities of the different growing seasons.