Evolution of paraquat resistance in barley grass (Hordeum leporinum Link. and H. glaucum Steud.)

摘要

The usefulness of herbicides can be eliminated by herbicide resistance in weed species. In Australia 25 weed species have been documented with resistance to one or more of nine herbicide groups. Two weedy barley grass species Hordeum glaucum Steud. and H. leporinum Link., infest crops and pastures in southern Australia. The intensive use of paraquat on these two species, principally in lucerne cropping and in grain crops, has resulted in the evolution of paraquat resistance at a number of sites in southern Australia. The evolution of paraquat resistance occurs after a prolonged period of use, often up to 20 years, suggesting that resistance genes are rare. A recent random survey of 50 Hordeum spp. populations from cropping fields in South Australiafound a single population of H. glaucum resistant to paraquat. This population is highly resistant (-200 fold) during winter conditions; however, resistance decreases under spring and summer conditions, suggesting that the resistance mechanism is strongly influenced by temperature. Knowledge of the variation both within and between populations enables genetic relationship to be established. Preliminary results using RAPD markers for both Hordeum spp. indicate that within population variation is low andthat RAPDs can be used to distinguish between these two species. This work will lead to a better understanding of the how resistance is spread as well as the evolution of paraquat resistance in field populations.