Frost tolerance in Acacia mearnsii: A review of past breeding research

Moreno Chan J
Publication Type
Publication Year

Acacia mearnsii de Wild (black wattle) is an important plantation species for bark extract production and woodchip exports in South Africa. The total area planted to black wattle in South Africa is currently 110 000 ha of which about 29% is located in areas prone to radiation frost in south-eastern Mpumalanga and northern KwaZulu-Natal. In the rest of the wattle-growing areas, including the KwaZulu-Natal Midlands, frost damage occurs in low-lying areas (frost hollows/pockets or valley bottoms). The economic impact of blanking and/or re-planting damaged compartments in frostprone areas is significant for individual farmers and the whole wattle industry.
Early work at the Natal Tanning Extract Company (NTE) and research at the Wattle Research Institute (WRI) (now the Institute for Commercial Forestry Research (ICFR)) has provided a good understanding of frost hardiness in black wattle. Past research at the WRI/ICFR has shown that only a very few Australian provenances can tolerate extreme frost events (i.e. temperatures of -8°C to -10°C), and has also characterised traits of economic importance (growth, stem form, bark quality and tolerance to gummosis) for several Australian provenances and seedlots. Over the past six decades, breeding efforts at the WRI/ICFR have remained at the seedlot or provenance level, and genetically improved seed for frost prone areas is not yet available for wattle growers. It is therefore necessary to accelerate breeding work in this area.
The purpose of this report is three-fold; firstly to understand frost hardiness in black wattle, secondly to provide a critical review of past breeding efforts and accurately ascertain the genetic material already introduced and tested on cold sites, and lastly to review work on alternative Acacia species and hybrids for frost tolerance. All these aspects are important for current and future breeding strategies.