Key points

• A new approach to managing Ascochyta blight in chickpeas is targeting inoculum build-up on stubble between seasons
• Microbial inoculants have shown efficacy against Ascochyta in initial laboratory studies
• The research is part of a broader plan to understand how Ascochyta rabiei inoculum builds up in both the local and broader regional environment

A new approach to improving chickpeas’ ‘high-maintenance’ reputation is targeting Ascochyta blight between cropping seasons.

Chickpeas have a reputation as a difficult crop to grow because Ascochyta blight can easily get out of control, reducing yield and quality. Limiting the impact of Ascochyta blight requires constant vigilance with in-season monitoring and often multiple fungicide applications. GRDC has now invested in a new approach to help chickpeas shake off their troublesome reputation.

The CSIRO-led research is investigating Ascochyta rabiei inoculum on stubble – between seasons – and has already identified potential management opportunities using microbial inoculants.

Microbial action

Microbial inoculants are used globally in row crops and horticultural industries to reduce the level of pathogen inoculum to control disease. Products can be fungal or bacterial, or in combination with the bioactive natural products they produce.

Modes of action can include:

• ability to outcompete the disease-causing pathogen;
• activity to enhance stubble breakdown; and
• production of antifungal chemicals.

CSIRO is testing microbial products from its own commercialisation pipeline and some existing commercial inoculants.

The four microbial inoculants have already shown efficacy against A. rabiei spores in initial laboratory ‘in-vitro’ studies. The process involved transforming A.rabiei with a fluorescent protein, which makes it easier to see and measure, and mixing the spores with different doses of the microbial inoculant. The efficacy of the inoculants was determined by measuring the growth of A. rabiei at different doses using fluorescent imaging technology.

The next step is to screen microbial inoculants for their activity against seed-borne inoculum and on stubble.

The research is part of a broader plan to take a ‘whole-of-system’ approach to understanding how Ascochyta rabiei inoculum builds up in both the local and broader regional environment and identify opportunities to reduce it.

While the initial results are promising, it is still early days and the products need to be proven to be effective, reliable and economically viable. Rates and application timing also need to be determined.

This alternate approach aims to reduce the build-up of inoculum on stubble during the off-season, thereby reducing the frequency and severity of epidemics. It is intended to complement the traditional detailed in-season fungicide management packages that are tailored to levels of genetic resistance.

Broader approach

The research is part of a broader plan to take a ‘whole-of-system’ approach to understanding how A. rabiei inoculum builds up in both the local and broader regional environment and identify opportunities to reduce it. This means understanding more about the factors that influence A. rabiei inoculum survival and growth on chickpea stubble outside the cropping season.

For instance, do different in-season control approaches – such as different levels of varietal resistance or fungicide usage – have an impact on the proliferation of inoculum out of season?

The aim is to develop a model that can analyse the cumulative effect of all the tools in the box – resistant varieties, fungicides, crop rotation and out-of-season inoculum management.

Ultimately, researchers hope the model will not only reduce the disease management burden but serve as a guide for future research investment.

The CSIRO researchers are working with Professor Rebecca Ford at Griffith University to access a range of A. rabiei strains as part of a suite of GRDC investments seeking to improve management of the disease.

More information: Dr Susie Sprague, 0466 643 227, susan.sprague@csiro.au; Dr Luke Barrett, 0419 563 789, luke.barrett@csiro.au