Finding genetic traits behind weed-competitive crops

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Identifying cultivars

CSIRO researchers have inserted above and below-ground traits that confer greater weed competitiveness into existing elite lines for supply to national breeding companies. As traditional wheat dwarfing genes reduce coleoptile length and subsequently early vigour, the program has also included alternative dwarfing genes that do not stunt coleoptile length. While commercial release of these varieties may still be eight years away, the non-destructive imaging system developed by the program will help breeders to identify weed-competitive cultivars during the breeding cycle. 

GRDC Research Code CSP00182

More information:

Greg Rebetzke,
02 6246 5153
greg.rebetzke@csiro.au

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.

Weed suppression

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.

Photo of canopy closure of Condo (left)

Complete canopy closure of Condo (pictured) at 113 days provided better weed suppression than that of the more open canopy of Espada (below).

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.

Crop vigour

Photo of open canopy of Espada (right)

Espada

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.

More information:

Professor Leslie A. Weston,
02 6933 4689,
leweston@csu.edu.au

Dr William B. Brown,
02 6933 4689,
wilbrown@csu.edu.au

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Beat down annual ryegrass – not your profit

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Essential guide to spray application

GRDC Project Code UCS00020, UCS00022, UCS00023; CSP00182

Region North