VARIATION IN PATHOGENICITY OF ISOLATES OF CERCOSPORA SPP ATTACKING HELIOTROPIUM SPP

The pathogenicity of a set of 13 Cercospora samples collected in Franc e, Turkey and Australia from four Heliotropium species has been evalua ted with a detached leaf technique. All of five Euro-Asian Heliotropiu m species tested were susceptible to all Cercospora species isolates. However, variation in the degree of partial resistance to different is olates was observed and showed some similarity for isolates from the s ame region of origin. Further studies are required to clarify the taxo nomy of Cercospora blight strains, but the consequences of the noted d ifferences in pathogenicity are discussed in relation to the biologica l control of H. europaeum L. in Australia.