Charles Sturt University
Graham Centre for Agricultural Innovation

Graduation: Understanding how wheat and canola can out-compete the weeds

Research by Charles Sturt University (Charles Sturt) PhD graduate Dr James Mwendwa has found early crop vigour and biomass accumulation are important traits in canola and wheat cultivars when it comes to suppressing weed growth.

Provost and DVC Academic Professor John Germov presents Dr Mwendwa with his PhDDr Mwendwa’s PhD through the Graham Centre for Agricultural Innovation involved field trials of wheat and canola at Condobolin and Wagga Wagga from 2014 to 2016.

Dr Mwendwa said it has provided fundamental knowledge about the mechanisms that allow some canola and wheat cultivars to interfere with the growth of broad-acre weeds.

“The field trials examined the above-ground canopy traits including early vigour, canopy closure, crop height, crop and weed biomass, and photosynthetically active radiation (PAR) light interception,” said Dr Mwendwa.

“I found that wheat cultivars with early crop vigour and biomass accumulation generally reduced weed biomass at both locations and over multiple years, suggesting these traits are associated with weed interference.

“The finding also suggests that establishment of competitive wheat cultivars can result in effective suppression of weed growth in the absence of herbicides.

“Similarly, the canola cultivars with the greatest biomass, PAR light interception, leaf area index and visual vigour were the most weed suppressive.

“Hybrid canola cultivars exhibited up to 50 per cent less weed biomass in contrast to open-pollinated cultivars.”

PhD graduate James MwendwaDr Mwendwa also studied what was happening below the ground in wheat crops, to evaluate the plants ability to exude chemicals into the soil around the roots as a defence mechanism against competition from neighbouring plants.

“The project analysed root tissue and soil samples around the roots to profile crop defence metabolites associated with weed suppression in commercial field-grown wheat under standard production practices,” said Dr Mwendwa.

“The findings indicate that these chemicals provide an additional mechanism for weed suppression but more research is needed to see if cultivars that produce these compounds can be targeted for enhanced weed control through biosynthetic modification.

“We also need to understand more about the role of soil microbiota and if they can be regulated to encourage the production and transformation of these potent chemicals.”

Dr Mwendwa was supervised by Professor Leslie Weston, Dr William Brown and Associate Professor Jane Quinn from Charles Sturt, Dr Hanwen Wu from the NSW Department of Primary Industries (DPI), and Professor Jeffrey Weidenhamer from the United States

His research is part of a Grains Research and Development Corporation (GRDC) investment in integrated weed management research at the Graham Centre.

Dr Mwendwa was be awarded his PhD in a ceremony at Charles Sturt in Wagga Wagga on Friday 13 December.