Control of bacterial wilt (Psuedomonas solanacearum) by agricultural biotechnology

• Montech, Australia
• University of Queensland, Australia

A major cause of crop losses in vegetables, potatoes, bananas, ground nuts, tobacco and other related crops in tropical regions of the world is Bacterial Wilt, caused by the bacterium P. solanacearum. This soil borne organism has a wide host range combined with high genetic variability. Controls to date have focussed on breeding for resistance and crop rotation practices. AVRDC is the major breeding institute for Bacterial Wilt in Asia for many affected crops and for example in tomatoes finds that a series of potentially resistant cultivars developed at AVRDC over many years, while resistant when grown at AVRDC show susceptibility when grown in the Philippines and Indonesia. Whether this is due to loss of resistance by the cultivars, a change in virulence characteristics of the organism or a location effect remains to be clarified. Linked with ACIAR project CS1/94/52 AVRDC will be involved with epidemiology experiments to correlate ecotypes, genotypes and genome variation in P. solanacearum. The approaches to be used will characterise the genomes of the major ecotypes of P. solanacearum contributing to bacterial wilt of tomato in the Philippines, Taiwan, Indonesia and Australia. Analysis of data to be obtained is expected to show DNA probes are able to provide technically simplified classification system which is of great use than those currently available.

First annual report was received on 16/10/96. CS1/94/52's work plan was finalised during the Bogor meeting. Responsibility of each collaborated institutes was discussed in detail and agreed by everyone. Dr Jaw-fen Wang at AVRDC is responsible for coordinating the subproject on 'Ecotyping of Pseudomonas solanacearum isolated from Agricultural areas and its implication for breeding of bacterial wilt resistant tomatoes". Master catalogues of strains of P. solanacearum for Indonesia, Malaysia, Philippines and Taiwan were finalised. Standard protocol for pathogenicity has been developed at AVRDC and distributed to collaborators. Boiled DNA of different aggressive strains were sent to Australia for developing new probes. Two collaborated scientists from Indonesia were trained in AVRDC Master Class on Bacterial Molecular Genetics. Following this master class the project was expanded to include Dr Nguyen Ngoc Cuong from Vietnam, ACIAR provided funds ($5,000) to purchase the necessary reagents to enable him to carry out PCR experiments with newly isolated strains of P. solanacearum obtained from tomato plants in Vietnam.