Breeding of weed-competitive wheat

Cathrine H Ingvordsen1, Tina Rathjen1, David J Smith2 & Greg J Rebetzke1

1 CSIRO, Agriculture and Food, PO Box 1700, Canberra, ACT, 2601,,,
2 CSIRO, Agriculture and Food, Private Mail Bag, Yanco, NSW, 2703


Weeds are estimated to cost Australian agriculture $4.3 billion a year. In Australia herbicide-resistant weeds are identified with increasing frequency, challenging current weed control methods. Competitive crop varieties are a little used weed control tool despite being low cost and easy to implement with other weed control approaches. Traditionally, Australian wheat varieties have not shown good early vigour, a trait representing more rapid leaf area development through wide leaves and greater biomass at stem elongation. Early vigour is a common mechanism of competition in natural plant communities and could be useful in managed farming systems. This paper describes a pre-breeding approach to develop Australian competitive wheat varieties. Overseas wheats with great early vigour were sourced and the vigour combined in one vigour-donor, which was crossed traditionally with adapted commercial varieties. The developed advanced breeding lines were assessed for agronomic parameters in rows in the field and then distributed amongst Australian commercial breeding companies. To date, ~5000 advanced main-season breeding lines have been distributed to Australian commercial breeding companies and evaluated by commercial breeders for uptake in their breeding programs. A further ~4000 advanced breeding lines including long-season types are under development for release in 2019-20. The feedback from commercial breeders on distributed advanced breeding lines has been positive.


Competitive wheats: does more vigour early matter?

Cathrine H Ingvordsen1, David J Smith2, Tina Rathjen1, Gurjet Gill3, Leslie A. Weston4, Washy Gapare1, Greg J Rebetzke1

1 CSIRO, Black Mountain Science and Innovation Park, Canberra, ACT, 2601,,, 2 CSIRO, Agriculture and Food, Private Mail Bag, Yanco, NSW, 2703, 3 The University of Adelaide, Waite Campus PMB 1, Glen Osmond, SA, 5064,4 Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW, 2678


Weeds are an ongoing challenge and herbicide-resistant weeds are on the rise. Incorporating weed-competitive varieties in the non-herbicide integrated weed management toolbox, make up a low cost and low risk approach to decrease the $4.3 billion weed costs Australian growers every year. We have assessed the competitive ability of a diverse set of 100 entries. The 100 entries vary from historic and modern wheat varieties to wheat lines developed to have wide leaves and greater biomass at stem elongation. Among the entries were also durum wheat, triticale and barley. The 100 entries were grown under field conditions in seven environments over three seasons with and without competition from oat or barley used as a weed-surrogate. Through in season measurements and separation of wheat grains and weed-surrogate grains after harvest we identified that wheats with wide leaves and greater biomass at early stem elongation only experienced yield decreases of 4-10% when grown in competition with weed-surrogate, whereas the best varieties decreased yield by 14% and worst decreased yield by 35%. Weed suppression was greatest in the high vigour lines.

Weed resistance and management in high break crop intensity rotations

Navneet Aggarwal1, Blake Gontar1, Amanda Pearce1, Brian Dzoma1, Arsego Fabio1, Penny Roberts1, Helena Oakey2, Peter Boutsalis2 and Larn McMurray3

1South Australian Research and Development Institute, 155 Main North Road, Clare SA 5453, email:,
2The University of Adelaide, Waite Campus, Urrbrae SA 5064, 3Global Grain Genetics, Clare, SA 5453


Controlling Group A and B herbicide resistant annual ryegrass and Group B resistant common sowthistle is becoming increasingly challenging in high break crop intensity (HBCI) systems in South Australia. Ryegrass resistance to recently released pre-emergence herbicides such as Boxer Gold® and Sakura® has been confirmed in HBCI systems. New herbicide Ultro® (active ingredient carbetamide, Group E), currently under development and expected for registration in 2020, provided significant control of dim-resistant ryegrass in lentils. Ultro® will offer an additional tool to support herbicides with alternative modes of action to control ryegrass in break crops. Imidazolinone resistant common sowthistle was detected in paddocks with and without Imidazolinone herbicides use in the past 5 years. Cross-resistance to sulfonylurea herbicides was also confirmed in common sowthistle. Increased crop competition offered by higher plant density of PBA Bendoc was found to have potential to reduce seed set of broadleaf weeds. The adoption of effective and diverse weed management strategies will aid in reducing the risk of resistance developing in HBCI rotations.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography Graham Centre for Agricultural Innovation, Charles Sturt University

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