A possible involvement of gibberellin in the mechanism of Avenafatua resistance to triallate and cross-resistance to difenzoquat |
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| Authors: | RASHID O'DONOVAN KHAN BLACKSHAW HARKER & PHARIS |
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| Institution: | Alberta Research Council, Bag 4000, Vegreville, AB, Canada T9C 1T4; Agriculture and Agri-food Canada Research Centre, Lethbridge, AB, Canada T1J 4B1; Agriculture and Agri-food Canada Research Centre, Lacombe, AB, Canada T0C 1S0; Plant Physiology Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 1N4 |
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| Abstract: | Avena fatua L. populations from numerous fields in Alberta have simultaneously developed resistance to recommended rates of two dissimilar herbicides, triallate and difenzoquat. We used exogenous applications of gibberellic acid (GA3) to investigate the possibility that endogenous gibberellins were involved in the A. fatua 's resistance mechanism. For control plants, without applied GA3, shoots of the most resistant (R) populations emerged more rapidly and elongated faster than shoots of the susceptible (S) populations. Increases in shoot elongation in response to exogenous GA3 were significantly lower in R populations compared with S populations. This suggests that R populations may have elevated endogenous gibberellin levels, relative to S populations. Additionally, inhibition of S population shoot elongation and shoot anatomical abnormalities caused by relatively low concentrations of triallate and difenzoquat could be prevented by exogenous application of GA3. These results suggest that there may be a phytohormonal involvement in the mechanism of triallate/difenzoquat resistance in A. fatua . That is, higher endogenous gibberellin levels in R populations may result in meristematic growth that is rapid enough to preclude phytotoxic levels of these herbicides from reaching the shoot meristem, which is the likely site of action. |
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