Economic returns from environmental problems: Breeding salt- and drought-tolerant eucalypts for salinity abatement and commercial forestry

Remediation of agricultural landscapes affected by salinity requires modification of land use practices to re-establish water balance at the catchment scale. Forest plantations established throughout the landscape, from recharge to discharge areas, have the potential to play an important role in this regard given their deep rooting habit, high perennial water use and low leakage of rainfall below the rootzone relative to annual crops. However, areas affected by salinity in Australia often present environmental conditions challenging to commercial growth. In 1996, the XylonovA R&D Syndicate commenced a collaborative breeding program to combine the salt and drought tolerance of Eucalyptus comaldulensis, with the growth rate, stem form and wood properties of the commercial species Eucalyptus grandis and Eucalyptus globulus. These hybrids exhibited heterosis under saline irrigated conditions, with the mean stem volume of hybrids at 85 months exceeding the best pure species parent by 140-252%. Gains in stem volume based on the mean of a commercial selection of hybrid clones ranged from 287 to 481%. Gains were more modest under non-saline, medium to low rainfall conditions (531-707 mm/year). Hybrid population means were similar to alternative pure species, but the hybrids were more stable across sites. Gains in mean stem volume from selection of the top 10% of hybrid clones over the best performing pure species ranged between 40 and 45%. The opportunity for commercial plantations of improved eucalypt hybrids integrated with agriculture in medium to low rainfall areas to address salinity and sustainability is discussed. (C) 2007 Elsevier B.V. All rights reserved