Individual Crown Selection for Resistance to Freezing Stress in Winter Oats 1

In recent years, crown freezing tests have been used to classify germplasm of small grain crops for resistance to freezing stress, a major component of winter hardiness. Selection has been based, however, on large numbers of crowns, and techniques for individual plant selection have not been developed. Our objective was to develop a system for growing and hardening winter oats ( Avena byzantina K. Koch and A. saliva L.) that will provide uniform expression of the freezing resistance trait and facilitate accurate individual crown selection. A technique of growing plants in individual tubes under controlled conditions of light, temperature, and moisture was developed. Individual crowns were frozen in capped vials on rotating shelves in a freezing chamber. Crowns that survived severe freezing stress and regenerated new roots were saved as selections. Effectiveness of the technique was tested by applying two cycles of crown selection to a four cultivar blend. After cycles 1 and 2, the mean injury scores of the population were 95.6 and 100%, respectively, of the most hardy component cultivar. In a second experiment, crowns of an F 6 bulk population were frozen and only 16 out of 640 survived. In subsequent tests of these lines, nine were equal to the hardy parent and 13 were equal or superior to the population mean. Thus, our crown selection technique provided a degree of precision that should be useful in breeding for increased resistance to freezing stress and improved winter hardiness.