Relationship between weed dormancy and herbicide rotations: implications in resistance evolution

Abstract

It is suggested that selection for late germinating seed cohorts is significantly associated with herbicide resistance in some cropping systems. In turn, it is conceivable that rotating herbicide modes of action selects for populations with mutations for increased secondary dormancy, thus partially overcoming the delaying effect of rotation on resistance evolution. Modified seed dormancy could affect management strategies - like herbicide rotation - that are used to prevent or control herbicide resistance. Here, we review the literature for data on seed dormancy and germination dynamics of herbicide-resistant versus susceptible plants. Few studies use plant material with similar genetic backgrounds, so there are few really comparative data. Increased dormancy and delayed germination may co-occur with resistance to ACCase inhibitors, but there is no clear-cut link with resistance to other herbicide classes. Population shifts are due in part to pleiotropic effects of the resistance genes, but interaction with the cropping system is also possible. We provide an example of a model simulation that accounts for genetic diversity in the dormancy trait, and subsequent consequences for various cropping systems. We strongly recommend adding more accurate and detailed mechanistic modelling to the current tools used today to predict the efficiency of prevention and management of herbicide resistance. These models should be validated through long-term experimental designs including mono-herbicide versus chemical rotation in the field. © 2017 Society of Chemical Industry.

Evolutionary and ecological insights from herbicide‐resistant weeds: what have we learned about plant adaptation, and what is left to uncover?

“…In one, researchers used a crossing design to homogenize the genetic background and found that A. myosuroides individuals with the Gly2078 ACCase resistance allele germinated earlier than wild-type individuals from the same genetic line (without the resistance allele). In comparison, lineages with a different resistance allele, Leu1781, exhibited delayed germination compared with wild-type (D elye et al, 2013b; Darmency et al, 2017). In the context of the Gly2078 allele, selection via herbicides should lead to the evolution of early germinators.…”

Dormancy, a critical trait for weed success in crop production systems

“…Thus, if this delayed sowing date is maintained for a number of years, a more dormant weed seed‐bank population will arise. As previously commented, selection for a higher level of dormancy due to selective pressure associated with pre‐sowing or early control practices has been reported by many authors …”

“…As for many others weed adaptive traits, agricultural practices also exert a strong selection on dormancy characteristics or levels . Preferable dormancy responses are those that allow weeds to survive in agroecosystems.…”

Does genetic variability in weeds respond to non‐chemical selection pressure in arable fields?

“…Much less is understood about responses to selection pressures other than herbicides, although there is increasing evidence in the literature for weed adaptation to non‐chemical control. For instance, there are many examples of within‐population variation in, and artificial selection for, seed dormancy (see references in Darmency et al ., ), including the observation that populations of Lolium rigidum in Australia delay germination in response to intensive cropping (Owen et al ., and references therein). There is also concern about the selection for shorter plants or earlier seed shedding in response to harvest weed seed control (HWSC, Walsh et al ., ).…”