Effect of Weather Variables During Maturation on Preharvest Sprouting of Hard White Wheat1

Abstract

Susceptibility to preharvest sprouting is a major disadvantage of hard white winter wheats (Triticum aestivum L.) as compared with most hard red winter wheat cultivars in the Great Plains. Experiments were initiated to determine differences in susceptibility among genotypes and to identify weather variables affecting preharvest sprouting. Seven white wheat lines and a popular red wheat cultivar were grown at several Kansas locations for 2 years. α‐Amylase enzyme activity was determined in grain from mature spikes before and after treatment with simulated rain. Multiple regression and stepwise regression analyses were used to determine the influence of accumulated temperatures, diurnal temperature fluctuations, and accumulated precipitation on α‐amylase activity before and after the rain treatment. The white wheat lines were uniformly susceptible to preharvest sprouting and the red wheat cultivar was more resistant, α‐Amylase activity before rain treatment was low 1 year and was high at all except one site the 2nd year, but activity in grain from all locations increased after rain treatment both years. Daily temperature fluctuations before physiological maturity and precipitation after physiological maturity significantly affected α‐amylase activity in wheat grain that was not treated with simulated rain. Regression coefficients of weather factors showed sprouting was increased by large daily temperature fluctuations, low daily temperatures, and high precipitation. We concluded that weather factors before as well as after physiological maturity affect preharvest sprouting resistance.