The plant growth regulator, trinexapac-ethyl, increases seed yield in annual ryegrass (Lolium multiflorum Lam.)

The plant growth regulator trinexapac-ethyl (TE) is widely used to increase seed yield by reducing lodging in many grass species, including perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.). However, the seed yield responses of annual ryegrass (Lolium multiflorum Lam.) to TE has not been widely investigated. In four field experiments, varying rates of TE (0 to 800 g ha-1) were applied and the plant response measured including components of yield and total seed yield. Seed yield was significantly (P<0.05) increased above the control by all TE treatments with an average response of 51% and 65% for the 200 g and 400 g TE ha-1 treatments, respectively. Seed yield did not increase further for TE rates above 400 g ha-1. Harvest mass and number of reproductive heads m-2 were unchanged. The seed yield response was associated with reduced lodging and shorter stems contributing to 72% more seeds m-2, increased conversion of fertile florets to saleable seed, more seeds per head and 74% more seeds per spikelet reaching a saleable weight. These data indicate the growth regulator TE can contribute to improved seed yield from well managed stands of annual ryegrass.