Wild chicks to check the 'todes by Gary Alcorn

Rotations and varietal selection are still best strategy while waiting for builtin resistance.

WILD RELATIVES are rarely welcome in most family situations but, when it comes to selecting superior chickpea varieties for pest resistance, exotic cousins could hold the answer.

Leading root lesion nematode (RLN) researcher John Thompson is currently assessing Cicer echinospermum and C. reticulatum from Turkey in his continuing quest to beat RLNs Pratylenchus thornei and P. neglectus.

These microscopic eel-like organisms enter fine crop roots and feed on nutrients destined for plant cell growth. High populations can depress grain yield in chickpeas and other crops by as much as 30 per cent. While nematicides can be used, the resulting RLN control and yield performance are highly variable.

The GRDC-supported Australian Coordinated Chickpea Improvement Program aims to develop natural nematode tolerance and resistance characteristics in this global pulse crop.

Since the program started in 1997, Dr Thompson and his team at the Leslie Institute in Toowoomba have been conducting both field and greenhouse trials to determine the most successful winter crop rotations when it comes to disrupting RLN populations.

Problem with nematicides

Applied nematicides are not mobile enough to control RLN populations deep in the soil profile, particularly in the heavy black and grey clay soils of the northern zone. The researchers have found nematode populations deep in the soil profile — 10, 000 per kg soil at 45 cm depth and 7, 000 per kg soil at 60 cm.

"It's up to the chickpea plant to carry its own protection which will suit countries demanding chemical-free food grains. "

"We have determined that in-built plant resistance is the most promising research area. Some of the wild relatives of commercial chickpeas have quite high resistance to RLN, so Ted Knights at Tamworth is crossing these to adapted varieties and we are selecting progeny with superior resistance, " he said.

So far Dr Thompson, working with program leader team Dr Knights, reports "excellent identified resistance in the progeny of crosses between various commercial chickpea varieties and C. echinospermum".

"This means with targeted plant breeding we can produce varieties with excellent resistance (rather than tolerance) to P. thornei and probably P. neglectus" he said.

All this takes time. What can growers do now to reduce the impact of RLN on next season's chickpea crop yields?

Interim strategy

Rotations and varietal selection have always played a major role in disrupting crop pest-breeding patterns both above and below ground.

  • Growing chickpea after nematode-resistant, vesicular-arbuscular mycorrhiza (VAM)-building crops such as canary seed (Phalaris canariensis) is a good option to avoid yield loss.
  • Wheat/chickpea rotations are not recommended in nematode-infested fields.
  • There is a wide range of RL tolerance and resistance in commercial chickpea varieties but none as good as that from the wild relatives.

Growers can have RLN population counts done on their paddocks to assist in crop choice decisions.

Program 2 Contact: Dr John Thompson 07 4639 8888 email John.Thompson@dpi.qld.gov.au