PREHARVEST SPROUTING IN WHEAT .1. INFLUENCE OF CULTIVAR, RAINFALL ANDTEMPERATURE DURING GRAIN RIPENING

Tolerance to pre-harvest sprouting, measured by the response of grain in intact harvested ears to a standard wetting treatment, varied subst antially from season to season and in all trials declined with time af ter harvest ripeness. The major factor associated with the observed va riation in tolerance at harvest and the decline after harvest ripeness appeared to be the level of grain germinability. Statistical analyses of meteorological data relating to the 10- and 20-day periods prior t o harvest and the period from harvest to wetting treatment, indicated that most of the seasonal variation in tolerance could be explained in terms of the amount of rain during the 20-day period prior to harvest . The potential to use this relationship to develop an early warning s ystem for wheat growers together with implications for wheat breeding and cultivar improvement programs are discussed.