Biological threats to Saccharum germplasm and sugar production in Papua New Guinea, Indonesia and Australia

• Indonesian Sugar Research Institute, Indonesia
• Ramu Sugar Ltd, Papua New Guinea
• Australian Quarantine Inspection Service, Australia
• Institute of Arable Crops Research, UK

Sugar cane (Saccharum species) is an important tropical crop both in Australia and in the wider region. The centre of origin of the genus is the island of New Guinea, which contains a rich diversity of germplasm.

Several serious diseases and pests of Saccharum occur in Irian Jaya and Papua New Guinea but not in the rest of Indonesia or in Australia. Conversely, some diseases occur elsewhere but not in Irian Jaya or Papua New Guinea. The various pests and diseases pose a great threat to commercial sugar production in all three countries, and especially worrying is their movement into new areas. Knowledge of the distribution of the pathogens and pests is still very scant and, in some cases, so are the details of their ecology.

The germplasm within the island of New Guinea is likely to be useful in counteracting the problems faced by commercial growers, as long as it can be used without bringing its pathogens with it. At an international conference on sugarcane quarantine and germplasm exchange in Brisbane in 1995, it was agreed that research was urgently needed on conserving Saccharum germplasm and on minimising the threats from its pests and diseases - which would include increased awareness and more effective methods of quarantine.

This project surveyed the distribution of pathogens and pests across the region, research the ecology and possible control measures for these biological threats, and provide the necessary lab equipment and training to improve research skills and quarantine operations in the region.

The aim of the project was to study the pests and diseases of sugar cane, and improve quarantine operations and the skills of researchers and quarantine officers in Australia, Indonesia and Papua New Guinea.

The work was divided into six subprojects and was coordinated by the Bureau of Sugar Experiment Station in Queensland.

The first subproject involved a survey of eastern Indonesia (including Irian Jaya), PNG and northern Australia to update the pest and pathogen status for each country. The greatest threats to commercial sugar production in each country were identified and realistic defensive strategies devised.

The second subproject identified ways of screening for resistance to the disease sugar cane smut. This involved the establishment of cooperative arrangements with Indonesia and a survey of the resistance status of some commercial cultivars.

A similar approach was used in the third subproject which examined resistance screening for the stalk-boring insect Sesamia. This pest could devastate the sugar cane industry in Australia or Indonesia.

Of equal seriousness is the disease Ramu stunt, which formed the subject of the fourth subproject. Ramu stunt was thought to be caused by a virus; the scientists hoped to confirm this and devise more sensitive methods of detecting the pathogen in plant tissue. This would then allow germplasm to be transported between countries without the risk of introducing the disease.

The fifth subproject identified unknown viruses or other infectious agents (such as phytoplasmas) in sugar cane germplasm in Indonesia and PNG.

The entire sixth subproject was devoted to training staff in pathology and entomology in all participating countries. This will provide the skills necessary to improve detection and identification of diseases and thereby upgrade quarantine procedures.

Regional surveys revealed significant new informtion about pest and disease distribution. For example, spread of hybrid material is leading to disease spread and loss of S. officinarum germplasm in PNG, Indonesia and Torres Strait Islands.

Variety selection trials showed that there are differences between varieties in susceptibility to shoot borer infestation; a number of varieties have been identified as standards (resistant and susceptible) in these trials and these will be used in future work.

The screening program has screened over 1000 clones for resistance to sugarcane smut and a high percentage of Australian clones were found to be susceptible to the disease.

Diseased leaves were imported through quarantine from Ramu Sugar into Australia for molecular assay work to develop a sensitive assay for the disease Ramu stunt for use in germplasm exchange.

Workshops were held in PNG, Torres Strait Islands and Indonesia to train quarantine staff. The first PNG sugarcane pest and disease manual, with photos and text, was produced and distributed to personnel at the PNG workshop. This will enable quarantine staff and others to become acquainted with sugarcane pest and disease issues. A similar manual was produced for Australian quarantine staff in the Torres Strait. Posters were produced in English, Motu and Pidgin to highlight quarantine issues in PNG.

The incidence of unknown forms of sugarcane mosaic virus in Indonesia and PNG were noted during the regional surveys.