STUDIES ON DROUGHT RESISTANCE IN SPRING WHEAT

Abstract

The results of a number of preliminary investigations regarding the nature of drought resistance in wheat are presented.A study of the susceptibility of wheat plants to drought at different stages of development showed that the shooting and the soft-dough periods were the most critical, from the point of view of grain yield. Heavy foliage losses occurred when plants were exposed during the shooting period, and recovery was very slow. Exposure of plants during the stooling stage resulted generally in transient injury, as the capacity for recovery was particularly great at this time. Plants subjected to drought during the hard-dough stage sacrificed little in kernel plumpness.Hardening of wheat plants by soil drought, or by limited exposures to atmospheric drought, increased their resistance to exposures of severe atmospheric drought.The drought-resistant varieties Milturum and Caesium were found to possess a more highly branched primary root system than the non-resistant varieties Marquis and Reward. The durum varieties, Pentad and Pelissier, were found to excel in numbers of primary roots produced, having an average of five per plant. Milturum, Caesium and Baart had more than four primary roots per plant on the average; while Canus, Federation, Reward, Marquis, Garnet and Red Bobs No. 222 had from 3.2 to 3.6. Reliance wheat and wild oats had not more than three primary roots per plant.The addition of superphosphate to the soil resulted in a slight decrease in number of primary roots of Milturum, Caesium and Marquis, and a slight increase in the number of Reward.The kernels of the drought-resistant varieties, Milturum and Caesium, did not show any marked superiority to those of Marquis, Reward, Garnet and Red Bobs No. 222, in capacity to germinate in the more concentrated solutions of sodium chloride, potassium chloride and sucrose. A higher energy of germination was displayed by the kernels of Milturum, Caesium and Garnet than by those of the other three varieties tested.Milturum and Canus exhibited high resistance to injury from windburn when tested m the late stooling to early shooting growth stages. The durum varieties Pentad and Kubanka and the soft wheat, Baart, on the other hand, showed high susceptibility. The soft wheat, Federation, and the variety Red Bobs No. 222 were moderately susceptible.