Studies on frost injury to wheat. I. Laboratory freezing tests in relation to the behaviour of varieties in the field

Abstract

Factors influencing the reactions of different varieties of wheat to stem and ear frosting were studied under controlled conditions and in the field. Artificial freezing tests were successful in demonstrating varietal differences in resistance, but these were not always in agreement with behaviour under commercial cultivation. Thus, whereas the American winter wheat Cheyenne showed resistance superior to that of the Australian varieties Bencubbin and Gabo, the observed superiority of Bencubbin over Gabo in the field was not maintained under controlled conditions. A possible explanation for this anomaly lies in the unequal distribution of temperature which obtains within a crop. On several frosty nights the ears and stems of Gabo, owing to their more forward development, were observed to be in a colder zone than those of Bencubbin. These conditions were not reproduced in the freezing cabinet, and comparisons between plants at different stages of growth failed to show any marked change in resistance with age up to the time of ear emergence. The relationship between temperature of freezing and degree of injury was established under different sets of conditions. In one case interaction between the effects of temperature and variety showed that this factor may be of some importance in the interpretation of results of freezing trials.