Biology subjects

Dorais, M.

Publications and source records attributed to Dorais, M..

3 recordsLinked to original sources

bioRxiv2023

Forest tree extracts induce resistance to Pseudomonas syringae pv. tomato in Arabidopsis

BackgroundThe widespread use of conventional pesticides to control plant fungal and bacterial pathogens poses significant risks to human health and the environment, and there is an urgent need for safer and more sustainable alternatives in agricultural management. Studies have shown that plant extracts can be effective in controlling plant diseases either by directly targeting the pathogens or by reinforcing the host plants own defenses. Here, we examined the potential of ethanolic extracts from forest tree species eastern hemlock, English oak, eastern red cedar and red pine for their antibacterial activity against Pseudomonas syringae pv. tomato (Pst) strain DC3000 and the ability of these forestry by-products to trigger effective defense responses in the model plant Arabidopsis thaliana. ResultsThe four tree extracts exhibited direct toxic effects against Pst DC3000, as notably observed for the English oak extract inhibiting bacterial growth and showing bactericidal activity at relatively low concentrations. Using an Arabidopsis line expressing reporter protein {beta}-glucuronidase under the control of a salicylic acid-inducible pathogenesis-related protein gene promoter, the extracts were shown also to induce defense-related genes expression in leaf tissue. RT-qPCR assays with DNA primers for different gene markers further confirmed this conclusion and highlighted gene-inducing effects for the tree extracts triggering, at different rates, the expression of salicylic acid- and oxidative stress-responsive genes. The extracts direct antibacterial effects, combined with their defense gene-inducing effects in planta, resulted in a strong host plant-protecting effect against Pst DC3000 associated with bacterial growth rates reduced by [~]75 to 98% seven days post-infection, depending on the extract. ConclusionsThese findings show the effectiveness of tree extracts as eventual plant protectants against the plant bacterial pathogen Pst. In a broader perspective, they suggest the potential of these forestry by-products as a source of bioactive compounds useful in plant protection and as a sustainable, eco-friendly alternative to conventional synthetic pesticides for the management of economically important plant pathogens.

plant biology↗

bioRxiv2023

Supplemental LED lighting improves plant growth without affecting biological control in a tri-trophic greenhouse system

Artificial lighting, including light-emitting diode (LED) illumination, is increasingly being optimized in protected agricultural systems to maximize plant yield and quality. However, it may also cause other top-down and bottom-up effects in these relatively simple ecological communities that also include insect pests and their natural enemies. While some effects of LED lighting on insects have been demonstrated to date, it is not known how they influence biological control of insect pests in practice. To examine potential top-down and bottom-up impacts of LED illumination on greenhouse biological control with parasitoids, we studied the effects of artificially lengthened days on a tri-trophic system in cages and in a greenhouse. We grew plants under a 12-hour photoperiod of white-supplemented light with 6 hours of additional 1) white light or 2) red and blue light, or 3) with no additional light. We exposed the plants to the pest aphid Myzus persicae (Hemiptera : Aphididae) with or without its parasitoid wasp Aphidius matricariae (Hymenoptera : Braconidae), or to no insects. The 18-hour light treatments increased mean plant dry mass by 127% compared with the 12-hour control without affecting the aphids population density or the parasitoids biological control efficacy under relatively low light conditions. This suggests that insect communities in protected agriculture can be resilient to even drastic changes in their light environment, and that adjusting crop lighting in a manner that affects plant growth does not necessarily compromise biological controls effectiveness.

ecology↗

bioRxiv2023

The effects of LED daylength extensions on the fecundity of the pest aphid Myzus persicae and the daily activity patterns of its parasitoid, Aphidius matricariae

Supplemental lighting, such as with LED lamps, allows greenhouse producers to maintain yields when natural light levels are low. Since both insect pests and their natural enemies are sensitive to light, both the duration and spectrum of LED daylength extensions could affect biological pest control in greenhouses. Longer days could allow for extended periods of reproduction for pests or foraging activity of biological control agents, possibly depending on the spectra used for these extensions. However, the effects of lengthening days with different LED spectra on the behaviour of biological control agents has mostly been studied in short-term experiments to date, and has not always included the context of the lights effect on their hosts reproduction. In growth chambers, we examined the locomotor activity of the parasitoid biocontrol agent Aphidius matricariae (Hymenoptera : Braconidae) as a predictor for foraging activity and the fecundity of its aphid host Myzus persicae (Hemiptera : Aphididae) over multiple days under different daylength extension regimes representative of those used in greenhouse vegetable production. We compared the effects of 14, 16, 18, and 20 h photoperiods, and 12 h days extended by 6 h with three different spectral qualities. The parasitoids adjusted how their activity was distributed throughout the lit period of the day (i.e., its total duration and peak timing) without changing the total amount of daily activity, regardless of the photoperiod or the light spectrum used for daylength extension. The aphids peak fecundity was not affected by photoperiod or spectral quality. Our results suggest that at least some behavioral and reproductive traits of these insects can be resilient to even drastic changes in their light environment.

ecology↗