Concurrent evolution of seed dormancy and herbicide resistance in field populations of dominant weed species in Western Australian cropping systems

Abstract

Herbicide resistance, documented in many economically-damaging weed species, is a major threat to global crop production. The injudicious use of herbicides, often in the absence of diverse weed control strategies, poses an immense selection pressure on weed communities for resistance evolution and weed adaptive traits such as high seed dormancy. This study evaluates the interaction among developing herbicide resistance, seed size and seed dormancy of ripgut brome (Bromus diandrus Roth), wild oat (Avena fatua L.) and hare barley (Hordeum leporinum Link; syn. Hordeum murinum L. ssp. leporinum (Link) Arcang.) collected from within intensively-managed fields (in-crop) in comparison with populations in surrounding ruderal (non-crop disturbed) areas with no history of exposure to herbicides within the Western Australian grainbelt. Seed size of the three species varied by farming system (continuous cereal-intensive annual crops, diverse annual crops, pasture-based) and habitat (in-crop, ruderal). Field populations of H. leporinum and B. diandrus tended to have greater seed size compared with ruderal populations. Larger seeds had significantly more dormancy in all three weed species. Field-collected populations that were exposed to herbicide applications for at least the past 5 years exhibited significantly greater seed dormancy compared with their counterparts present in ruderal areas within the same geographical area. The association between increased seed dormancy and developing multiple herbicide resistance further complicates effective weed management.

Diversified germination strategies of Centaurea cyanus populations resistant to ALS inhibitors

“…Different patterns of the germination timing within and between populations indicate the development of adaptive traits by plants in response to different environmental conditions in which they grew, and may suggest the influence of crop management practices on the selection of germination and emergence of weed strategies (Owen et al 2010). The dynamics of germination and emergence are dependent on the seed dormancy period, which is longer in herbicide-treated populations than in populations occurring in ruderal habitats (Maity et al 2022). In our study, part of the plants from T4 belonging to populations 8401 and 9307, showed the smallest reduction in biomass after the florasulam application, indicating that they originated from seeds with a longer dormancy period.…”

“…Adequate germination timing allows the seedlings to avoid pre-sowing practices and to emerge under the best possible conditions for growth (Riemens et al 2022). Knowledge concerning the germination process of resistant plants can be helpful in determining the strategy of preventing the selection and eradication of resistant biotypes (Maity et al 2022).…”