Continued analyses of the effect of silicon on Fusarium wilt on banana (BA10024)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Fusarium wilt at the time caused large losses in banana production worldwide. In Australia Ladyfinger and Ducasse production was affected by race 1 strains of the Fusarium wilt fungus whereas Cavendish production until recently (2012) was only affected in south east Queensland and northern NSW where subtropical race 4 of the fungus was present. However in the Northern Territory, Cavendish had succumbed to tropical race 4 of the Fusarium wilt fungus. There was increasing concern that this particularly aggressive strain could have devastated Cavendish production in Northern Queensland if accidently introduced to that region.

In our investigations to look at the interaction of the Fusarium wilt fungus with banana and to assess possible control methods, we examined the potential use of silicon supplements. We previously showed that when silicon was applied either in tissue culture or as a supplement to small pot plants that subsequent Fusarium wilt disease levels were reduced.

In this current study we investigated where the silicon was deposited in the plant tissues when added as a supplement. We found that the silicon was taken up and deposited throughout the root tissue but that the highest levels were in the zone known as the inner cortex. It was possibly in this zone where the plant was required to exhibit its greatest defence against the invading Fusarium wilt fungus.

We have also determined that certain pathogenicity genes previously identified in the strains of the Fusarium wilt fungus that attack tomato were also present in strains that attack banana. Significantly these pathogenicity genes were absent in the non-pathogenic strains we assessed providing further evidence that they were important in causing disease. We also noted a variation in these pathogenicity genes within the strains that attacked bananas allowing us to distinguishes race 1 and race 4 isolates and further analysis was conducted that allowed us to distinguish tropical (TR4) and non-tropical (ST4) strains of race 4. This provided a very useful tool for molecular diagnostics and also led to a better understanding of the mechanism of pathogenicity of Fusarium wilt which should ultimately allowed for better control strategies.

In our tests on the wild banana line Malaccensis that exhibited resistance to Fusarium wilt we discovered that the resistance was effective against all known pathogenic races of the Fusarium wilt fungus on banana. Work was continued as to allow us to develop a marker for this resistance which could ultimately be used in a banana breeding programme with the aim of producing commercially acceptable Fusarium wilt resistant banana plants.