By Tony Pattison, Department of Agriculture and Fisheries (DAF), South Johnstone
Panama disease Tropical Race 4 (TR4) was first found in the Tully valley in March 2015.
The unknowns surrounding this discovery left banana growers and the future of the Australian banana industry in a precarious position. Actions were taken to increase awareness and improve farm biosecurity in the short-term. However, investments were also made to look at long-term solutions for the worst-case scenario, if Panama disease could not be contained.
The project The Fusarium wilt Tropical Race 4 Research Project was a result of that investment and has recently been completed.
So where has this investment left the Australian banana industry in terms of its ability to deal with Panama disease?
The Fusarium wilt TR4 Research Program set about to develop long-term management strategies, which meant that the outcomes from the research would not impact on banana growers until 5-15 years after the project was started. In establishing the project there were three main themes;
1. Prevention – through strengthening onfarm biosecurity tools,
2. Resilience – by providing growers with knowledge and awareness of practices that could suppress Panama disease and;
3. Resistance – through the development of banana cultivars with improved resistance and acceptability for the Australian banana industry.
The prevention of Panama disease builds on biosecurity outcomes from previous projects. The aim was to provide Australian banana growers with improved capability to prevent Panama disease spreading further.
• On-farm biosecurity options for banana growers have been enhanced by developing an on-line version of the BMP Biosecurity manual, https://bmp.abgc.org.au/
• QBAN clean planting material scheme to ensure provision of clean, disease-free planting material has also been enhanced by conversion to an industry led program.
A Panama disease resilient farming system aims to slow the progress of the disease. The basis of a resilient production system has been developed by understanding the plant-pathogen-microbe interactions, the infection process and how inoculum can build up in the soil.
The identification of the core microbiome of bananas benchmarks a microbial community for healthy banana plants. Where the core microbial community can be maintained or enhanced, Panama disease progress is slowed, and symptoms are less readily displayed. This tends to occur in north Queensland banana soils which have a higher clay content, increased vegetated ground cover and where nitrogen fertilisers are not overused. Fusarium species, like the organism that causes Panama disease, are a dominant part of the banana soil fungal community. It is when the microbial competition is reduced or disrupted that the Panama disease organism can dominate to rapidly infect plants. The “disruptors” to a stable microbial community can be environmental stresses, such as weather extremes, heat, cold, waterlogging and drought, and those imposed by management practices, such as nutritional deficiencies, excessive nitrogen, poor soil management, soil acidity, loss of microbial diversity and tillage. Further work on understanding how to manage the banana soil microbial community is continuing in another project.
All plants found within banana plantations, such as weeds and ground covers, have the potential to host the Panama disease organism. A guide for banana growers has been produced to help understand the potential that other plants have for retaining Panama disease in banana paddocks.
Banana cultivars with improved resistance are the foundation to continuing banana production where TR4 has become widespread. The project used a mutation breeding approach, called mutagenesis, to develop improved banana varieties with TR4 resistance. The mutagenesis program has demonstrated that it is possible to have a relatively low budget banana improvement program using the available resources within Australia. The basis for the improvement program was commencing with cultivars that already have some resistance to TR4, and selecting plants with improved agronomic characteristics. This approach has allowed banana lines with potential suitability for Australian production to be selected, with improved TR4 resistance and productivity equivalent to Williams. The successful cultivars at the basis of the improvement approach were the Cavendish varieties GCTCV 119, CJ19 and GCTCV 215. All retained their resistance to TR4.
The cultivar Goldfinger, which is highly resistant to TR4, was also used in the mutagenesis process to improve the fruit’s eating characteristics. The on-going cultivar improvement process is now continuing in another banana levy funded project.
The Fusarium TR4 Research Program has built a strong foundation for the Australian banana industry to manage Panama disease with minimal impact on production. It has been a collaboration between state agricultural agencies and universities to fast track technological advances in science into applied agricultural research.
The project has contributed to the national exposure of the problem of TR4 and shown to an international audience how the Australian banana industry has been proactive in combating the problem.
The full final report for the project can be accessed through Hort Innovation https:// www.horticulture.com.au/growers/help-yourbusiness-grow/research-reports-publicationsfact-sheets-and-more/ba14014/