Progress in selection and production of jarrah (Eucalyptus marginata) resistant to Phytophthora cinnamomi for use in rehabilitation plantings

Resistance to Phytophthora cinnamomi in jarrah (Eucalyptus marginata) is under strong genetic control. It has high heritability, is probably polygenic, and is durable in field trials. Seedlings from healthy mother trees, either growing on long-tenn dieback sites or from a provenance collection made across the range of the species, were grown in the glasshouse and resistant seedlings selected from inoculation trials. These were micropropagated by tissue culture. The resulting clonal lines were planted in field validation trials on dieback-affected sites and soil at the base of the plants was also inoculated with P.'cinnamomi to test survival and growth of resistant plants. In spite of some drought deaths, survival of most resistant lines has been high. Some 45 unrelated resistant lines have been selected. However, due to high costs of production and establishment problems in forest sites, it is not feasible to use the clonal jarrah directly in large-scale operational plantings. Clonal seed orchards are now being planted to supply seed of resistant jarrah for use in the rehabilitation of dieback-affected forest and plantings on cleared land