The aims of the project are to:
collect and exchange citrus rootstock material, including species native to China and Australia, local clonal selections and hybrids arising from breeding programs; and
cooperate in the evaluation of potential rootstock material with respect to isozyme analysis, disease tolerance, salt tolerance and horticultural attributes.
For disease tolerance, attention will be focused on Phytophthora infection and tristeza. Pathogenic strains of the citrus tristeza virus (CTV) and species of the fungus Phytophthora vary in each country.
Citrus industries depend on the availability of suitable rootstocks. In both China and Australia, salinity and alkalinity problems are concerns in citrus-producing areas. Researchers are seeking improved, disease-tolerant rootstocks that will adapt to local soil and climatic conditions.
Chinese scientists are now establishing arboreta of wild citrus relatives in Hunan and Sichuan Provinces, using isozyme analysis to help identify native species, and are evaluating selections in field trials. Wild citrus collected in south-western China with potential as rootstocks include Poncirus trifoliata variants, natural P. trifoliata hybrids, several Fortunella species, wild mandarins, and selections of Citrus ichangensis and C. junos.
Australian expertise in rootstock evaluation is widely recognised. Research programs have been enhanced by improved identification of local selections, importations from overseas breeding programs, and limited introductions from areas where citrus originated (China, India and Southeast Asia). The only citrus native to Australia are Microcitrus, Eremocitrus and Clymenia.