IMPROVEMENT OF WINTER HARDINESS IN OAT FROM 1935 TO 1992

The Uniform Oat Winter Hardiness Nursery was initiated in 1926 to improve the probability of selecting more winter-hardy oat (Avena sativa L.) germplasm under field conditions. The nursery has been grown at 141 locations in 31 U.S. states and four Canadian provinces and 986 cultivars and experimental Lines have been tested. Survival data from 1935 to 1992 was used to (i) summarize nursery information, and (ii) evaluate progress in winter hardiness improvement. Analysis of variance (ANOVA) for 10 check cultivars revealed four hardiness categories. Analysis of the same 10 checks by the method of pairwise rank superiority confirmed the relative rankings from the ANOVA results. Regression analyses from more than 1000 location-years in which differential winter killing occurred indicated significant genetic improvement in average winter hardiness of entries submitted for testing during the first 35 yr (1935 to 1970); the hardiness of elite entries has improved throughout the period of analysis (1935 to 1992) at an estimated rate of 0.26% per year. The decreased progress in average hardiness of entries since the mid1970s may be a result of reduced effort in breeding for winter hardiness due to lack of funding and/or exhaustion of genetic potential.