New varieties lead fight against ‘sneaky’ root rot
By Bernie Reppel
NSW Agriculture’s Tamworth-based chickpea team – breeder Ted Knights and pathologists Ron Southwell and Kevin Moore – believe they have Ascochyta blight (AB) pretty well licked, but worry about the damage potential of phytophthora root rot (PRR) and botrytis grey mould (BGM).
Phytophthora root rot, according to Mr Knights, is endemic across the north and “such a sneaky disease, like tooth decay you don’t know you have. It can cut yields by 10 percent without you being able to see it’s there”.
“You can’t spray for PRR. Once you’ve got it, there’s nothing you can do about it,” explains Dr Moore. “If chickpeas get infected with botrytis grey mould or Ascochyta blight, and conditions cease to be favourable for the disease, there’s a possibility of the plants recovering. Most PRR infected plants succumb.”
Five years ago an outbreak of AB rendered much of the northern region’s prerelease chickpea genetic material almost obsolete, and the two varieties released since then – Howzat and Jimbour– remain susceptible to the disease.
Management strategies developed by the industry, including a strict fungicide spray program, have allowed growers to manage AB in these varieties, although they do add to production costs.
“In a couple of years we are going to move from a situation of having chickpea varieties that sustain serious yield loss if they’re not sprayed in years favourable to AB, to varieties which, in most years, may require no fungicide sprays at all,” Dr Moore says.
“If new varieties to be released in 2005-06 reduce the need for fungicides – as we expect they will – botrytis grey mould could emerge as the next major challenge. Its importance hasn’t been appreciated in the north in recent years, because the AB management strategy has also controlled BGM.
“Unfortunately, seasons that favour high chickpea yield also favour BGM and managing it will be essential if farmers are to capture the yield potential of those good years.
“We need to know the extent of BGM’s potential to reduce yields and depending on that, may need to have a management plan in place to coincide with the release of the new varieties, because they are susceptible to BGM.”
It is something of a juggling act for Ted Knights to incorporate the different disease resistances into new chickpea varieties; they also have to meet industry quality standards for the grain.
The northern chickpea industry has displayed a readiness to almost totally replace older varieties with Jimbour and Howzat, along with the widespread adoption of associated management packages. This gives Mr Knights confidence that future varieties, with a better balanced combination of Ascochyta and PRR resistance, will meet with similar acceptance.
Jimbour, for example, can increase yield by as much as 80 percent in PRR infected situations, but it cannot eliminate losses altogether.
“We have two lines for release in 2005 – line ball with the current varieties for all the necessary characteristics – with significantly better AB resistances than Howzat and Jimbour. There is also an improvement in PRR resistance but not as big as for AB,” Mr Knights says.
“The line 9113-13N-2 will be released for the areas of northern NSW west of the Newell Highway, where the pressure from PRR is more likely than AB.
“93011-1021 will suit the better areas east of the Newell Highway, where the relative importance of the two diseases reverses.
“It’s fair to say our control of AB is better than that of PRR, but there is material in the breeding program much more resistant to PRR and readily accessible.” 3
For more information:
Dr Kevin Moore & Mr Ted Knights 02 6763 1100
GRDC Research Code: DAN 442, program
Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.