Challenges in sunflower breeding for cold tolerance

Аннотация

Introduction. Sunflower is grown as an oilseed crop worldwide. For sunflower production, it is vital to have cold-tolerant hybrids. An appropriate method to assess cold tolerance is a prerequisite for successful breeding of cold-tolerant sunflower.

Purpose and Objectives. To evaluate cold tolerance of sunflower in the laboratory and its tolerance in the field, to identify promising combinations, to assess the capacity of a laboratory test to predict tolerance of sunflower in the field and to verify relationships of cold tolerance with ripeness group and yield.

Materials and Methods. Sunflower was grown in compliance with standard farming techniques. In total, 192 F₁ hybrids were obtained. The lines and hybrids were screened for ability to germinate at above-zero low temperature by laboratory test. The field tolerance  at the initial stages of plant growth was determined with a 9-point scale. Relationships between the investigated parameters were analyzed by linear regression.

Results and Discussion. The highest field tolerance at the initial stages of plant growth was recorded for Kh4713V, Skh777А and Skh808А lines. However, they only conferred tolerance to some of their hybrids. On the other hand, several hybrids were fairly tolerant in the field though the tolerance scores of their parental lines ranged 1 to 5 points. There was no relationship between the ‘emergence – anthesis’ period and cold tolerance. A great degree of uncertainty is associated with predicting field tolerance of sunflower from its cold tolerance assessed by laboratory test. This laboratory test cannot be used to predict field tolerance of either lines or hybrids. There was a strong positive correlation between the field tolerance and seed yield in the lines, but the correlation coefficient for the hybrids indicated no significant correlation between these parameters.

Conclusions. At non-freezing low temperatures, the yield of the inbred sunflower lines was positively correlated with the field tolerance score at the early stages of plant growth and development. There was no significant difference in responses of early- and medium-ripening sunflower genotypes to cold exposure. Lakhanov’s cold germination test is not appropriate for evaluation of field tolerance in sunflower lines and hybrids.