Submission Type
Poster
Abstract
The symbiotic mutualism between plants and rhizobial bacteria that occurs within root nodules, wherein plants supply rhizobia with carbon in exchange for biologically fixed nitrogen, provides critical ecosystem services via plant growth promotion and nutrient cycling. However, it is unknown how contemporary anthropogenic stressors such as pesticide pollution affects this important ecological relationship. We grew red clover (Trifolium pratense) from 17 genetic families in the greenhouse either alone or in symbiosis with one of two rhizobial strains. We exposed half to a sublethal rate of the herbicide dicamba, equivalent to what wild plants experience when herbicides ‘drift’ off-target by wind, or a control solution. We characterized immediate foliar damage, characteristics of the plant-rhizobia interaction, and plant fitness based on biomass, and assessed whether responses to herbicide drift were influenced by plant family, rhizobial inoculation/strain, or their combination. We found that plant family and rhizobial inoculation interacted to mitigate the foliar damage plants incurred immediately following drift exposure. Aspects of the plant-rhizobia interaction in terms of quantity (nodule number) and quality (nitrogen fixation) were influenced by the joint effects of plant family, rhizobial strain, and herbicide treatment, or only the latter interaction (nodule size). Drift also significantly reduced plant fitness similarly across plant and rhizobial pairings. Altogether, these findings suggest that low levels of herbicide stress can not only significantly impact plant health but also plant-microbe symbioses; however, the magnitude and direction of these impacts often depend on the genetic backgrounds of both plant and microbe.
Impacts of herbicide drift on the plant-rhizobia mutualism is dependent on genetic variation in both mutualists
The symbiotic mutualism between plants and rhizobial bacteria that occurs within root nodules, wherein plants supply rhizobia with carbon in exchange for biologically fixed nitrogen, provides critical ecosystem services via plant growth promotion and nutrient cycling. However, it is unknown how contemporary anthropogenic stressors such as pesticide pollution affects this important ecological relationship. We grew red clover (Trifolium pratense) from 17 genetic families in the greenhouse either alone or in symbiosis with one of two rhizobial strains. We exposed half to a sublethal rate of the herbicide dicamba, equivalent to what wild plants experience when herbicides ‘drift’ off-target by wind, or a control solution. We characterized immediate foliar damage, characteristics of the plant-rhizobia interaction, and plant fitness based on biomass, and assessed whether responses to herbicide drift were influenced by plant family, rhizobial inoculation/strain, or their combination. We found that plant family and rhizobial inoculation interacted to mitigate the foliar damage plants incurred immediately following drift exposure. Aspects of the plant-rhizobia interaction in terms of quantity (nodule number) and quality (nitrogen fixation) were influenced by the joint effects of plant family, rhizobial strain, and herbicide treatment, or only the latter interaction (nodule size). Drift also significantly reduced plant fitness similarly across plant and rhizobial pairings. Altogether, these findings suggest that low levels of herbicide stress can not only significantly impact plant health but also plant-microbe symbioses; however, the magnitude and direction of these impacts often depend on the genetic backgrounds of both plant and microbe.
Comments
Elizabeth M. Rarick (University of Pittsburgh, Pittsburgh, PA, USA)
Tia-Lynn Ashman (University of Pittsburgh, Pittsburgh, PA, USA)