Galic, N. | bioRxiv Science

bioRxiv2024

Effects of maize development and phenology on the field infestation dynamics of the European Corn Borer

Phenological match/mismatch between cultivated plants and their pest could impact pest infestastion dynamics in the field. To explore how such match/mismatch of plant and pest phenologies may interact with plant defense dynamics, we studied the infestation dynamics of maize by one of its main pests in Europe, the European Corn Borer (Ostrinia nubilalis; Lepidoptera: Crambidae). A two-year field experiment was carried out on a collection of 23 maize inbred lines contrasted for their earliness. Each inbred line was sown at three different dates in order to expose different developmental stages of maize to natural European corn borer infestation. The effect of the sowing date depended on the inbred line, the pest generation and the year. In 2021, the final pest incidence ranged from 36% to 91% depending on inbred lines and sowing date. In 2022, it ranged from 2% to 77%. This variability in final pest incidence can be related to variations in plant development during plant exposure to pest infestation. However, this relationship was not straightforward. Indeed, the shape and intensity of the relationship depended on the timing of the onset of the pest infestation. When infestation occurred while plants were in a vegetative stage, a non-linear relationship between development and pest incidence was observed with the least and most developed plants being the most infested. When infestation occurred when all plants were in the mature phase, the most developed plants were the least infested. Our results highlight the effect of plant-pest phenological match/mismatch on pest infestation dynamics and underline the importance of taking plant-pest interactions into account to propose relevant control strategies.

ecology↗

bioRxiv2023

The coupling between mutations effects and environment guides the exploration of the phenotypic space as evidenced in artificial selection experiments

Quantitative genetics models have shown that long-term selection responses depend on initial variance and mutational influx. Understanding limits of selection requires quantifying the role of mutational variance. However, correlative responses to selection on non-focal traits can perturb the selection response on the focal trait; and generations are often confounded with selection environments so that genotype by environment (GxE) interactions are ignored. The Saclay Divergent Selection Experiments (DSE) on maize flowering time were used to track the fate of individual mutations combining genotyping data and phenotyping data from yearly measurements (DSEYM) and common garden experiments (DSECG) with four objectives (1) to quantify the relative contribution of standing and mutational variance to the selection response, (2) to estimate genotypic mutation effects, (3) to study the impact of GxE interactions in the selection response, (4) to analyze how trait correlations modulate the exploration of the phenotypic space. We validated experimentally the expected enrichment of fixed beneficial mutations with an average effect of +0.278 and +0.299 days to flowering, depending on the genetic background. Fixation of unfavorable mutations reached up to 25% of incoming mutations, a genetic load possibly due to antagonistic pleiotropy, whereby mutations fixed in the selection environment (DSEYM) turned to be unfavorable in the evaluation environment (DSECG). Global patterns of trait correlations were conserved across genetic backgrounds but exhibited temporal patterns. Traits weakly or uncorrelated with flowering time triggered stochastic exploration of the phenotypic space, owing to microenvironment-specific fixation of standing variants and pleiotropic mutational input.

evolutionary biology↗