Breakthrough with chickpea disease

Technical officer, Paul Nash, and technical assistant, Gail Chiplin, members of the research team working on Phytophthora root rot research at Tamworth, conducting parallel screening in Jiffy pots in the glasshouse.
Technical officer, Paul Nash, and technical assistant, Gail Chiplin, members of the research team working on Phytophthora root rot research at Tamworth, conducting parallel screening in Jiffy pots in the glasshouse.

A breakthrough has been achieved in the quest to breed chickpea varieties with improved resistance to the most significant disease of chickpeas in northern NSW, Phytophthora root rot.

Chickpeas are the major pulse grown in the north, and the NSW Department of Primary Industries (DPI) is seeking to increase plantings to improve the sustainability of cropping rotations.

Whilst a wild species (Cicer echinospermum) was already known to have greatly improved resistance, and crosses with chickpeas had been made, it was not known which of the species’ progeny carried the resistance genes.

Research by DPI plant pathologist Kevin Moore, chickpea breeder Ted Knights, technical staff Paul Nash and Gail Chiplin at Tamworth appears to have overcome these limitations.

Instead of artificially infesting screening nurseries with Phytophthora root rot (PRR)grown on oat/barley kernels under dryland conditions, researchers are now mimicking the conditions under which the disease will develop and become sufficiently infective to aid research.

An irrigated site has been established at Breeza which allows the nurseries to be flood irrigated at a stage when disease expression is most likely.

A second site has also been set up near Warwick in southern Queensland.

The team has also developed a new form of inoculating the nurseries which consists of growing Phytophthora in the laboratory on a medium that produces oospores. These are the natural survival structures of Phytophthora and also the source of infection.

DPI plant pathologist Kevin Moore, who heads the project, said experiments in the glasshouse and field have shown that oospores are more effective than oat/barley kernels in inducing PRR.

“Even better, oospore inoculum can be produced in less space than the oat/barley inoculum and requires less time - three weeks instead of twelve,” Dr Moore said.

“Thanks mainly to the efforts of Paul Nash and Gail Chiplin, parallel screening in Jiffy pots in the glasshouse is now being considered.

“This will enable many more genotypes to be screened in as little as four weeks, as only one set of field nurseries can be evaluated each season.”

He said results in the past have been variable, partly because PRR requires saturated soil to infect and develop and also because the oat/barley kernel inoculum has not always been sufficiently infective.

While the Australian chickpea breeding program at Tamworth Agricultural Institute has made significant progress in developing varieties with improved resistance to PRR, the best variety currently available, Yorker, will still die under high disease pressure.

Unlike Ascochyta blight, which can be controlled in crop with foliar fungicides, nothing can be done to help a chickpea crop that has PRR. Once a plant is infected with the Phytophthora organism, it usually dies.

Current recommendations for minimising losses from PRR include avoiding paddocks with a history of PRR, seed treatment and variety selection.
However, seed treatment only offers protection early in the year so a crop can still be lost later in the season.

The research has been funded by the Grains Research and Development Corporation.