Logit models for estimating lethal temperatures in apple

Abstract

Logit models were used to analyze freeze-survival data of apple (Malus domestica Borkh.). The effects of hardening and dehardening treatments and two treatment durations on lethal temperature were studied using two cultivars. The major benefits of logit models were 1) the form of the sampling variation in the qualitative response variable was taken into account, 2) the lethal temperatures could be estimated with confidence intervals, and 3) the effects of treatments could be interpreted and compared easily using odds ratios. The momentary frost resistance estimates for 'Antonovka' and 'Samo' were -46 and -43C, respectively. Dehardening at 14C raised the lethal temperature by 12 to 15C, whereas hardening at -15C did not affect the frost resistance of either cultivar.