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Research shows canola’s allelopathic potential against annual ryegrass

PhD student Md Asaduzzaman and Professor Jim Pratley

A study by Charles Sturt University at Wagga Wagga has demonstrated the canola plant’s potential to naturally suppress annual ryegrass growth through chemical interference – also known as allelopathy.

The research, headed by CSU research professor in agriculture Jim Pratley and funded by Advanta Seeds, established allelopathy as a potential future supplement to synthetic herbicides.

“The introduction of herbicide tolerant canola varieties is a significant advance for the crop and the farmers who grow them, but the risk of herbicide resistance is enhanced as key herbicides, notably glyphosate, are transformed in use from the first herbicide in a cropping season to the last and perhaps the only herbicide,” Prof Pratley said.

“The simplification of herbicide use therefore is a threat to the stability in availability of herbicides.

“The results found that most of the canola genotypes evaluated significantly reduced the root growth of ryegrass with increasing density.”

Prof Pratley said the background of the study centred on the fact that crop production in Australia is highly dependent on herbicides to provide effective weed control; however, numerous weed species have evolved resistance to several herbicide modes of action.

“The most notable is annual ryegrass (Lolium rigidum) where resistance is widespread geographically and the range of herbicides affected is extensive.”

He said plants have long had the capability to compete with other species in varying degrees, and one mechanism is for the plant to exude chemicals into the root environment to inhibit the competing plants.

“The competing species will be doing the same thing and the winner will be the one which has the most potency to its competitors while also being tolerant of the chemicals being exuded by those competitors.”

This process is known as allelopathy and the chemicals involved are called allelochemicals.

Hyola hybrids were evaluated as part of the Equal Compartment Agar Method (ECAM) laboratory work, which is a simple and rapid evaluation of plant capability.

“The technique has been widely used and its correlation with field performance has been tested for both rice and canola,” Prof Pratley said.

“This provides a reasonable basis for identifying allelopathy which otherwise is challenging to distinguish from other interference mechanisms such as competitive ability under field conditions.”

Advanta Seeds canola business manager Justin Kudnig said the most suppressive genotype was Hyola 404RR – a popular Roundup Ready hybrid marketed by the company.

“Hyola 404RR resulted in 72 per cent root growth inhibition of annual ryegrass, followed by genotype Hyola 970CL, at 70pc, slightly ahead of the high allelopathy control line at 68pc.

“Hybrids such as Hyola 650TT, Hyola 559TT, Hyola 600RR, Hyola 577CL, Hyola 525RT and Hyola 725RT showed moderate to high allelopathic potential, which is a great result.”

The weakest of the lines evaluated were the open pollinated canola varieties such as Thumper TT and Crusher TT.

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