Bacteria plant growth puzzle

Photo of Grains Research scholar - Vanessa Conn

By Rebecca Thyer

Re-inoculating healthy wheat plants with natural bacteria that live within the plant can promote plant growth and potentially boost grain yield, scientists at South Australia"s Flinders University are discovering.

Actinobacteria are found in soil and play important roles in decomposition and humus formation. But it is their role in promoting plant growth that is intriguing scientists such as biotechnologist and Grains Research Scholar Vanessa Conn. The Flinders University PhD student and her team have isolated actinobacteria from inside wheat roots and found that re-inoculating healthy wheat plants with the bacteria "actually promotes plant growth" while enhancing disease resistance.

[Photo: Vanessa Conn]

"At the moment we don"t know how this is happening, and my role has been to understand the molecular mechanisms behind this interaction," Mrs Conn says.

Any process that can boost growth promotion is obviously important to the grains industry, she says. "The rapid establishment of roots increases seedlings ability to anchor to the soil and to obtain water and nutrients from their environment, therefore enhancing their chances of survival and minimising the opportunity for pathogen infection."

In the absence of disease pressure, the team also found that grain yield increases of five to 14 per cent were possible through re-inoculation, due to growth promotion activity.

"Growth promotion compounds are often plant growth hormones and it was found that many of our endophytic strains are able to produce high levels of the plant growth promoter indole acetic acid (IAA)," Mrs Conn says.

Additionally, re-inoculation causes the plant to turn on its defence system. "Plants have a way of defending themselves through a process called ‘systematic acquired resistance" (SAR) or induced systemic resistance.

"When a plant encounters a pathogen it activates a defensive pathway. Re-inoculating wheat plants ensures this defence pathway is switched on, meaning it has a better chance of warding off other pathogens."

The process has been shown to work in the laboratory model plant Arabidopsis thaliana, a weed from the mustard family. And while a lot of work has been successful on this model, the next step is to isolate the compound responsible, Mrs Conn says. "If we can isolate that, it will really advance our work."

Research work to find a successful biocontrol agent is proving to be difficult. "Our pot trials have been successful and now we are working on field trials."

Mrs Conn finds understanding how plants operate an exciting task. "I wanted to go into research that had a clear focus or outcome. I did my undergraduate degree in biotechnology at Flinders University and decided to continue with my PhD here too," she says. "Eventually, I"d love to work overseas and continue my work in plant research. "

GRDC Research Code GRS49
For more information: Vanessa Conn, 08 8204 8970,