Defferential Agronomic Response of Winter Wheat Cultivars to Preanthesis Environmental Stress

Winter wheat (Triticum aestivum L.) cultivars produced in the semiarid environment of the Canadian prairies are subjected to variable water stresses. Therefore, successful cultivars in this region require both a high production potential and yield stability. This study was initiated to compare the agronomic performance of two winter wheat cultivars that had demonstrated a differential response to the often high drought stress environment of Saskatchewan. Eleven field trials were conducted at seven locations in Saskatchewan from 1984 to 1987. Measurements included dry matter production, yield components, grain yield, harvest index, water use, and water use efficiency. Pan evaporation during the 15-d period immediately prior to anthesis (E) ranged from 64 to 158 mm for the 11 trials and was used as an indicator of environmental stress. There was a significant (P < 0.01) negative relationship between grain yield and E for both cultivars. The difference in grain yield between cultivars (Norwin minus Norstar) ranged from approximately 500 to −1500 kg ha⁻¹. As stress increased, the grain yield for Norwin declined at a significantly higher rate than that of Norstar. The differential response of these cultivars to stress was related to differences in kernel number m⁻² (KNO). Under high E (approximately 8.0 mm d⁻¹), KNO for both cultivars was associated with preanthesis dry matter production. Under low E (approximately 5.0 mm d⁻¹), significantly higher KNO for Norwin was attributed to a more favorable preanthesis dry matter distribution (KNO per unit of aerial dry matter present at anthesis) compared to Norstar. Other factors that contributed to the observed genotype by environment interaction were harvest index and water use efficiency (kg grain ha⁻¹ mm⁻¹ evapotranspiration). M. H. Entz present address: Dep. of Plant Science, Univ. of Manitoba, Winnipeg, MB, R3T 2N2, Canada. Supported in part by a grant from the New Crop Development Fund of Agriculture Canada and in part by a grant from the Canada-Saskatchewan Economic Regional Dev. Agreement.