Exploiting the clonal variability of Chondrilla juncea to detect virulent strains of Puccinia chondrillina for use in Australia

The use of P. chondrillina, a rust fungus, as a biocontrol agent for skeleton weed (C. juncea) has resulted in stable control of the most prevalent clone of that weed in Australia. However, the two other clones occurring there have remained unaffected due to the extreme specificity of the imported strain of the rust. Recent large scale collections from Eurasia have emphazised the inherent difficulty in finding specific strains that would be efficient against the resistant forms in Australia. Consequently, isozymes have been used to discriminate the Eurasian clones of the weed and to determine their relationships to the Australian clones, thus indicating the probable origin of the latter and also sources of potentially useful strains of the rust.