Diallel Analyses of Winterhardiness in Peas 1

The parental lines and 36 F 2 populations obtained from a nonreciprocal diallel cross among nine lines of peas [ Pisum sativum L. and P. sativum subsp. arvense (L.) Poir] were evaluated for winterhardiness in the field at Moscow, Idaho and for freezing tolerance in a programmable freezer at −3 and −6 C. Combining ability analyses indicated that general combining ability (GCA) played a significant role in conditioning survival under both field and laboratory conditions. The ratio of sum of squares for GCA and GCA plus specific combining ability (SCA) ranged from 0.59 to 0.87, indicating there was sufficient GCA in these populations to allow successful selection for winterhardiness. Under field conditions the lines ‘Melrose’ and ID 2 exhibited high levels of winterhardiness, had high mean parental effects and large estimated GCA effects which indicate these lines were good parents for winterhardiness. Although the three spring lines did not differ in winterhardiness in the field, the mean parental effects and estimated GCA effects of ‘Tracer’ indicated this line was a better parent to use in crosses with winter‐hardy parents than the other two spring lines. Although differential survival was measured in laboratory evaluations of freezing tolerance, the results were not as distinct as in the field evaluation. Correlation coefficients of only 0.55** and 0.59** (Significant at the 0.01 level.) were measured between percent survival in the field and percent survival at −3 and −6 C, respectively. Because survival in the field is dependent on factors other than freezing tolerance, such as soil drainage, snow cover, and disease infection, these relatively low correlation coefficients were expected. Final selection for winter survival should be made under field conditions.