IMPROVEMENT OF WINTER HARDINESS IN OAT FROM 1935 TO 1992

The Uniform Oat Winter Hardiness Nursery was initiated in 1926 to impr ove 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 culti vars and experimental Lines have been tested. Survival data from 1935 to 1992 was used to (i) summarize nursery information, and (ii) evalua te progress in winter hardiness improvement. Analysis of variance (ANO VA) for 10 check cultivars revealed four hardiness categories. Analysi s of the same 10 checks by the method of pairwise rank superiority con firmed the relative rankings from the ANOVA results. Regression analys es from more than 1000 location-years in which differential winter kil ling occurred indicated significant genetic improvement in average win ter 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% p er 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 potentia l.