Directional selection for flowering time leads to adaptive evolution in Raphanus raphanistrum (Wild radish)

Abstract

Herbicides have been the primary tool for controlling large populations of yield depleting weeds from agro‐ecosystems, resulting in the evolution of widespread herbicide resistance. In response, nonherbicidal techniques have been developed which intercept weed seeds at harvest before they enter the soil seed bank. However, the efficiency of these techniques allows an intense selection for any trait that enables weeds to evade collection, with early‐flowering ecotypes considered likely to result in early seed shedding. Using a field‐collected wild radish population, five recurrent generations were selected for early maturity and three generations for late maturity. Phenology associated with flowering time and growth traits were measured. Our results demonstrate the adaptive capacity of wild radish to halve its time to flowering following five generations of early‐flowering selection. Early‐maturing phenotypes had reduced height and biomass at maturity, leading to less competitive, more prostrate growth forms. Following three generations of late‐flowering selection, wild radish doubled its time to flowering time leading to increased biomass and flowering height at maturity. This study demonstrates the potential for the rapid evolution in growth traits in response to highly effective seed collection techniques that imposed a selection on weed populations within agro‐ecosystems at harvest.

Modelling crop-weed competition: Why, what, how and what lies ahead?

“…Or we may be more interested in the longer term impacts of the changes to competition, such as the long-term seedbank and population dynamics; resulting changes in future weed management that will be required, such as smaller seedbanks needing fewer herbicide applications; resulting changes to the land use options possible in the system, such as larger seedbanks needing pasture phases to control weed populations; and the overall longterm profitability and sustainability of the system (Holst et al, 2007;Renton and Lawes, 2009). We may even be interested in the impacts of competition on long-term evolutionary dynamics, such as evolution of herbicide resistance or selective shifts in plant structure, phenology, or dormancy (Ashworth et al, 2014(Ashworth et al, , 2016.…”

“…In another exciting future development, we will see modelling of the evolutionary dynamics of more complex phenotypic characteristics under control of a larger number of genes, such as morphology, phenology, and the way that the whole plant structure emerges over time as a result of genetic factors interacting with environmental factors (Renton and Poot, 2014;Renton, 2013). For example, it will become possible to simulate how weed plant growth and phenology will change over generations under selection from harvest seed management (Ashworth et al, 2014(Ashworth et al, , 2016, how this will cause changes in plant structure and thus crop-weed competition, and how this will feed back to alter selection and evolution. As we move ahead, we must also remember the limits of modelling.…”

Morphological differences among Raphanus raphanistrum populations and their relationship to related crops

“…The Nordic DM population had early flowering compared to the other populations from lower latitudes. Latitude gradient in flowering is a frequent feature, and phenological adaptation was already demonstrated in wild radish (Ashworth, Walsh, Flower, Vila‐Aiub, & Powles, ). Differences in vegetative and reproductive performances were much more marked among populations under high interspecific competition and natural pollinators in the oilseed rape field than under low intraspecific interference and abundant presence of a non‐specific pollinator (the domestic fly) in the cages.…”

An ecological perspective on managing weeds during the great selection for herbicide resistance

“…Currently, HWSC tactics have been rigorously evaluated and implemented in various production systems across the globe as a tool for managing herbicide‐resistant weeds . However, they are not a panacea; evolutionary adaptation is very likely for these management tactics when relied upon heavily, through a shift towards early maturity (and shattering) and/or prostrate growth habit. Therefore, a strong consideration to evolutionary processes is critical in developing sustainable weed management solutions …”