How weeds defend themselves against one of the most widely used herbicides

How weeds defend themselves against one of the most widely used herbicides

Until now, it was unknown why one of the most used herbicides in olive groves and citrus groves in Spain and, above all, in the Andalusian community, hardly affects the speciesLolium rigidum, one of the most problematic weeds for these crops and one that keeps more than one farmer awake.

A team of researchers from the University of Córdoba (UCO), led by the professor of Agricultural Chemistry and Soil Science Rafael A. De Prado, has discovered that a biotype of this species is resistant to a herbicide widely used in crops, glyphosate . This resistance is due to the fact that, when the pesticide is applied on the weed, it is absorbed and moves little with respect to the susceptible biotype.

The resistance of these weeds
glyphosate is not associated with human actions
nor to weather phenomena

Since the 90s, glyphosate has been used continuously, widely used in olive groves and citrus groves throughout the Spanish geography. This situation led to this herbicide causing selection pressure on two large types of weedsLolium rigidum YConyzaspp. As a result, the first of these weeds have been able to survive glyphosate treatment at doses that should kill it.

Laboratory tests

In the study published in the journalFrontiers in Plant Science The team of scientists verified, by using Carbon 14 and a system called Phosphor Imager, how glyphosate barely penetrates and moves inside the plant. Thus, the non-translocation of the herbicide is actually a defense mechanism of the plant itself. De Prado explains that to reach these results, they conducted surveys, mainly in olive groves in the province of Jaén and citrus groves in Córdoba, Seville and Huelva.

Imitating the contrast CT scans that are done daily in hospitals, the UCO researchers applied theLolium rigidum the field dose of glyphosate herbicide mixed with Carbon 14 and after 96 hours a radiographic image of the plant was taken where they verified that glyphosate is not translocated by certain parts of the weed in question.

Research shows that the resistance of these weeds to glyphosate is not associated with human actions or climatological phenomena, but is something intrinsic in the adapting plant. The team now wonders whether this same mechanism is repeated in other species and with other herbicides.

Bibliographic reference:

Fernández-Moreno, PT; Bastida, F; De Prado, R. "Evidence, Mechanism and Alternative Chemical Seedbank-Level Control of Glyphosate Resistance of a Rigid Ryegrass (Lolium rigidum) Biotype from Southern Spain".Frontiers in Plant Science March 8, 2017


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