Finding genetic traits behind weed-competitive crops
GroundCover™ Supplement Issue: 128 May - June 2017 | Author: William B. Brown, James Mwendwa, Graeme Heath and Leslie A. Weston
While getting the agronomy right is central to crop competitiveness, the GRDC is also investing in the search for the genetic traits that make some varieties more naturally competitive than others. As more weed populations become resistant to knockdown and post-emergent herbicides, selecting crops with a natural competitive ability is increasingly important in the overall mix of weed control options.
Researchers at Charles Sturt University (CSU) at Wagga Wagga in NSW have identified commercial grain cultivars with characteristics that are highly weed suppressive and competitive. Some crop species and cultivars consistently suppress weeds at standard establishment rates.
The project is also evaluating early breeding material from the CSIRO pre-breeding program led by Greg Rebetzke, which was profiled in the last GroundCoverTMSupplement on wheat pre-breeding (see box).
While weed competitiveness has not traditionally been considered a priority for breeders or growers, interest is building in the potential for combining competitiveness traits with other agronomic advances.
For example, competitive crops that reduce weed growth also have better access to limited resources such as nutrients and soil water.
Each year since 2012, CSU researchers have collected data at the critical plant developmental stages of mid-tillering, stem elongation, flowering, maturity and post-harvest residue to determine which traits are associated with in-crop and post-harvest weed suppression. These included physical characteristics, percentage light interception, the amount of green vegetation through normalised difference vegetative index (NDVI) readings, biomass of crop and weeds, vigour, yield and post-harvest weed suppression.
They have found that crop height and vigour are important early in the season for strongly competitive crops and subsequent weed suppression. Additionally, tillering characteristics, above and below-ground canopy and root architecture, rate of maturity and partitioning of resources are important for overall crop competitiveness (see photos, right).
These characteristics not only suppress weeds but also provide greater yield potential by providing the crop with greater access to nutrients and moisture.
The role of soil microbial communities in weed suppression is also under evaluation. This project will provide information to plant breeders to enable them to incorporate weed-suppressive traits into commercial breeding programs.
Professor Leslie A. Weston,
02 6933 4689,
Dr William B. Brown,
02 6933 4689,
GRDC Project Code UCS00020, UCS00022, UCS00023; CSP00182
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