Biology subjects

Armstrong, M. R.

Publications and source records attributed to Armstrong, M. R..

4 recordsLinked to original sources

bioRxiv2026

Tolerance to herbicide drift in "weedy" species is context-dependent and driven by early vegetative growth

While plant communities that exist at the edges of agricultural fields are typically composed of 'weedy' species, they provide essential resources for insect pollinators and other wildlife. However, little is known about how sublethal exposures to herbicides via drift (off-target chemical movement by air) affects the fitness of weedy plant species across varying agro-ecological environments. If weed species vary in sensitivity to herbicide drift, then this could result in plant community shifts in favor of more tolerant species. Consequently, these changes in species composition could alter resource availability in agroecosystems. Here, we replicated a common garden experiment in three US states where agriculture is a major form of land use (Michigan, Pennsylvania, and Tennessee). We exposed nine weed species to a sublethal, drift-level rate of the herbicide dicamba and examined plant fitness. We found that fitness in the presence of dicamba drift depended on both the weed species and the environmental context. For some species, dicamba drift significantly reduced fitness. For others, it had no effect, indicating greater tolerance to the herbicide. However, more variation in tolerance to dicamba drift among species was observed in Michigan compared to Pennsylvania or Tennessee, a result that was partially explained by the severity of damage from insect herbivory that occurred at each location. In a follow-up study, we explored the relationships between plant developmental traits and fitness to determine the functional pathways that underlie tolerance to dicamba drift using structural equation modeling. This approach revealed that weedy plants that are better able to buffer the effects of dicamba drift on short-term growth are then better equipped to minimize effects on flower production and ultimately fitness (seed set). Overall, our work advances knowledge about how wild plant populations in different contexts are responding to unintentional, yet increasingly common occurrences of anthropogenic stress in the form of off-target herbicide exposures.

ecology↗

bioRxiv2024

Off-target drift of the herbicide dicamba disrupts plant-pollinator interactions via novel pathways

Assessing the impact of herbicide drift on plant-pollinator interactions is crucial for providing insight into the causes of ongoing pollinator declines. The recent exponential increase in the use of the synthetic auxin herbicide dicamba, which is known to drift long distances following application, renders this concern especially acute. However, experimental data on the consequences of dicamba drift on plant-pollinator interactions are lacking from weed communities in natural settings. We assessed the indirect effects of dicamba drift on pollinator visits for 11 weeds of agricultural crops using a common garden field experiment, focusing on the potential for changes in pollinator abundance and alterations to both plant traits and patterns of pollinator visitation. We found variation among plant species in the extent of damage from dicamba drift exposure, and variation in how growth, flowering time, and flower displays were impacted, with some species showing negative impacts and others showing little effect. Pollinator frequencies were reduced in dicamba-exposed plots, and pollinator approaches and foraging visits were reduced for some weed species yet not others. Structural equation modeling revealed that the relationship between flower display and pollinator visits was disrupted in the presence of dicamba compared to control plots. Our study provides the most comprehensive picture to date of the impacts of dicamba drift on plant-pollinator interactions, with findings that highlight an underappreciated role of services supplied by weedy communities at the agroecological interface.

ecology↗

bioRxiv2022

SMRT-AgRenSeq-d in potato (Solanum tuberosum) identifies candidates for the nematode resistance Gpa5

Potato is the third most important food crop in the world. Diverse pathogens threaten sustainable crop production but can be controlled, in many cases, through the deployment of disease resistance genes belonging to the family of nucleotide-binding, leucine-rich-repeat (NLR) genes. To identify functional NLRs in established varieties, we have successfully established SMRT-AgRenSeq in tetraploid potatoes and have further enhanced the methodology by including dRenSeq in an approach that we term SMRT-AgRenSeq-d. The inclusion of dRenSeq enables the filtering of candidates after the association analysis by establishing a presence/absence matrix across resistant and susceptible potatoes that is translated into an F1 score. Using a SMRT-RenSeq based sequence representation of the NLRome from the cultivar Innovator, SMRT-AgRenSeq-d analyses reliably identified the late blight resistance benchmark genes R1, R2-like, R3a and R3b in a panel of 117 varieties with variable phenotype penetrations. All benchmark genes were identified with an F1 score of 1 which indicates absolute linkage in the panel. When applied to the elusive nematode disease resistance gene Gpa5 that controls the Potato Cyst Nematode (PCN) species Globodera pallida (pathotypes Pa2/3), SMRT-AgRenSeq-d identified nine strong candidates. These map to the previously established position on potato chromosome 5 and are potential homologs of the late blight resistance gene R1. Assuming that NLRs are involved in controlling many types of resistances, SMRT-AgRenSeq-d can readily be applied to diverse crops and pathogen systems. In potato, SMRT-AgRenSeq-d lends itself, for example, to further study the elusive PCN resistances H1 or H3 for which phenotypic data exist.

plant biology↗

bioRxiv2018

Tracking disease resistance deployment in potato breeding by enrichment sequencing

Following the molecular characterisation of functional disease resistance genes in recent years, methods to track and verify the integrity of multiple genes in varieties are needed for crop improvement through resistance stacking. Diagnostic resistance gene enrichment sequencing (dRenSeq) enables the high-confidence identification and complete sequence validation of known functional resistance genes in crops. As demonstrated for tetraploid potato varieties, the methodology is more robust and cost-effective in monitoring resistances than whole-genome sequencing and can be used to appraise (trans)gene integrity efficiently. All currently known NB-LRRs effective against viruses, nematodes and the late blight pathogen Phytophthora infestans can be tracked with dRenSeq in potato and hitherto unknown polymorphisms have been identified. The methodology provides a means to improve the speed and efficiency of future disease resistance breeding in crops by directing parental and progeny selection towards effective combinations of resistance genes.

plant biology↗