Plant Damage after Freezing, and the Frost Resistance of Varieties from the Facultative and Winter Wheat Observation Nurseries

Abstract

In the first experiments, studies were made on the survival % of four winter wheat varieties with good frost resistance and two with poor frost resistance, and on the degree of plant damage after freezing at −14°C and −16°C under phytotron conditions. In the second experiment the frost resistance of the varieties included in the 9^th Facultative and Winter Wheat Observation Nurseries (FAWWON) was determined after freezing in the phytotron at −15°C. The scores gave a good reflection of the variety ranking determined on the basis of survival % and of the different effects of the two freezing temperatures. On the basis of the scores, the plants were divided into two groups for each treatment and each variety: plants which suffered frost damage (a score of 2–3), and plants which suffered no frost damage (a score of 4–5).

Twenty plants from each group were raised to maturity in pots. The yield parameters of plants damaged by freezing at −14°C were reduced to a lesser extent than those frozen at −16°C. Of the eight parameters tested, the reduction in the number of ears per plant and consequently in the number of grains in the side ears, the grain mass and the total grain yield, gave the clearest indication of the extent of plant damage. The results of the second experiment indicated that in some cases the frost resistance of the varieties could be predicted from the wheat production zone (e.g. varieties from Eastern Europe and Nebraska have excellent frost resistance), while in other zones winter hardiness and frost resistance depended rather on the country or on the breeding location.