Abstract:

rost often causes young ear injury at the elongation stage of wheat, the frost-sensitive period, leading to yield reduction. The objectives of this study were to understand how frost resistance of young ears (FRYE) varied with development progression to find the most frost-sensitive stage, and the factors affecting the FRYE, which is of importance for determining the feasible phase to evaluate the frost resistance of different wheat cultivars and, providing guidance to select the cultivars with frost resistance, as well as developing the frost prevention technologies. In this study, change in FRYE with development progression was investigated with 4 cultivars of winter wheat (Triticum aestivum L.), using the Movable Artificial Climate Chamber. Frost resistance of young ears of 21 cultivars were tested at earlier stage of anther connective formation phase (ACFP) using the Room Climate Chamber and the effects of several factors on FRYE, such as cultivars, varietal types, winter hardiness, and soluble sugar content of leaves were analyzed. Degree of injury was examined using the microscopes. The results showed that there was a decreasing trend for FRYE with process of development and a sharp drop at the beginning of ACFP, suggesting that the sensitive phase to low temperature for young ears started with ACFP. Frost resistance of young ears closely related to development progression, and difference in frost injury among cultivars was mostly caused by differences in plant development progression; no significant differences could be found among most of the cultivars, except a few ones with a strong frost resistance; no significant correlations existed between varietal pattern and FRYEs, between FRYEs and winter hardiness, and between FRYEs and soluble sugar contents of leaves. Therefore, evaluation of FRYE and selection of cultivars with frost resistance need to perform in same development stage, especially in the frost-sensitive stage. And some indices for winter hardiness can not be used to estimate frost resistance of cultivars.

Key words: Winter wheat, Young ear, Frost resistance, development stage