Metarhizium anisopliae isolates from several insect hosts and from various sugar cane growing areas of Queensland, Australia, were examined for genetic diversity using random amplified polymorphic DNA (RAPD) markers. Thirty isolates of M. anisopliae var. anisopliae and one isolate of M. anisopliae var. majus were examined. Ten randomly chosen 10mer or 11mer primers were used and RAPD banding patterns were compared. Thirty distinct genotypes could be distinguished amongst the 31 isolates tested on the basis of RAPD patterns. Six of the isolates classified as M. anisopliae var. anisopliae exhibited closer similarity to the M. anisopliae var. majus isolate than to other anisopliae strains tested. Isolates exhibiting similar (> 80% similarity) RAPD profiles tended to be isolated from the same geographic area and evidence for the persistence of particular fungal genotypes in specific geographical localities was obtained. Pathogenicity assays suggested that, in some instances, RAPD groupings may also indicate insect host range. The mean similarity amongst isolates measured by band sharing in all pairwise comparisons was 41% and the most distinct pair of isolates shared only 9% of their RAPD bands. We conclude that the isolates tested belonging to the species M. anisopliae, as assessed on morphological grounds, represent a very diverse genetic group. The results also suggest that RAPD markers may be useful for the tracking of specific biocontrol strains in the field.

Phytophthora diseases cause major losses to agricultural and horticultural production in Australia and worldwide. Most Phytophthora diseas

Breeding methodologies for cultivated lucerne ( Medicago sativa L.), an autotetraploid, have changed little over the last 50 years, with reliance on polycross methods and recurrent phenotypic selection. There has been, however, an increase in our understanding of lucerne biology, in particular the genetic relationships between members of the M. sativa complex, as deduced by DNA analysis. Also, the differences in breeding behaviour and vigour of diploids versus autotetraploids, and the underlying genetic causes, are discussed in relation to lucerne improvement. Medicago falcata , a member of the M. sativa complex, has contributed substantially to lucerne improvement in North America, and its diverse genetics would appear to have been under-utilised in Australian programs over the last two decades, despite the reduced need for tolerance to freezing injury in Australian environments. Breeding of lucerne in Australia only commenced on a large scale in 1977, driven by an urgent need to introgress aphid resistance into adapted backgrounds. The release in the early 1980s of lucernes with multiple pest and disease resistance (aphids, Phytophthora , Colletotrichum) had a significant effect on increasing lucerne productivity and persistence in eastern Australia, with yield increases under high disease pressure of up to 300% being recorded over the predominant Australian cultivar, up to 1977, Hunter River. Since that period, irrigated lucerne yields have plateaued, highlighting the need to identify breeding objectives, technologies, and the germplasm that will create new opportunities for increasing performance. This review discusses major goals for lucerne improvement programs in Australia, and provides indications of the germplasm sources and technologies that are likely to deliver the desired outcomes.