Selection for extreme frost resistance

AFOCEL commenced a breeding programme for Eucalyptus in 1972 after several tentative species introductions had been undertaken by the Administration Porestiere Francaise. Introductions of Eucalyptus into France had been stopped previously because of the exceptionally cold winter of 1956. Interest in eucalypt plantations for pulpwood production increased following the success of trials established near Toulouse, in the south of France (Marquestuat et al. 1978. Marien and Cauvin 1984) and was encouraged by more than a century of growth of eucalypts as ornamentals near the Mediterranean coast. The good growth rates and survival of species such as Eucalyptus datrympleana. E. viminalis, E. macarthurii and E. nitens as well as the slower growing, but more frost resistant species such as E. gunnii resulted in the development of an intensive eucalypt breeding programme (Cauvin 1984; Cauvin et at. 1987) and approximately 400 hectares of industrial plantings of clonal selections had been established prior to the devastating frost of 1985 (Figure 1). Up until the winter of 1985,considered as extreme as that of 1956. AFOCEL had proposed a group of clones for the industrial plantations which principally comprised E. gunnii x dalrympleana hybrids. These clones represented what, at the time, was considered an acceptable compromise between vigour and frost resistance given the low probability of another extreme winter. However, since the frost of 1985 which killed even the more frost resistant species such as E. gunnii to ground level (potts and Potts 1986). industrial plantings were stopped and AFOCEL has since concentrated on selection of eucalypt clones for extreme frost resistance. AFOCEL is selecting close to the natural limits of the frost resistance of the genus and the challenge is to develop plants which are resistant to relatively infrequent, unpredictable extreme frost temperatures; yet suitably productive to remain economically competitive with more traditional species.