ABSTRACT
This paper considers the statistical analysis of entomological count data from field experiments with genetically modified (GM) plants. Such trials are carried out to assess environmental safety. Potential effects on nontarget organisms (NTOs), as indicators of biodiversity, are investigated. The European Food Safety Authority (EFSA) gives broad guidance on the environmental risk assessment (ERA) of GM plants. Field experiments must contain suitable comparator crops as a benchmark for the assessment of designated endpoints. In this paper, a detailed protocol is proposed to perform data analysis for the purpose of assessing environmental safety. The protocol includes the specification of a list of endpoints and their hierarchical relations, the specification of intended levels of data analysis, and the specification of provisional limits of concern to decide on the need for further investigation. The protocol emphasizes a graphical representation of estimates and confidence intervals for the ratio of mean abundances for the GM plant and its comparator crop. Interpretation relies mainly on equivalence testing in which confidence intervals are compared with the limits of concern. The proposed methodology is illustrated with entomological count data resulting from multiyear, multilocation field trials. A cisgenically modified potato line (with enhanced resistance to late blight disease) was compared to the original conventional potato variety in the Netherlands and Ireland in two successive years (2013, 2014). It is shown that the protocol encompasses alternative schemes for safety assessment resulting from different research questions and/or expert choices. Graphical displays of equivalence testing at several hierarchical levels and their interpretation are presented for one of these schemes. The proposed approaches should be of help in the ERA of GM or other novel plants.
ABSTRACT
Insect-plant interactions may be unintentionally affected when introducing genetically modified (GM) crops into an agro-ecosystem. Our aim was to test the non-target effects of a late blight-resistant GM potato on Myzus persicae in greenhouse and climate room experiments and understand how position and number of R gene insertions can affect non-targets in GM events. We also aimed to compare results to baseline differences among three conventional potato varieties varying in resistance to late blight. Aphid development and survival were affected by some GM events in the first generation, though effects disappeared in the second generation. Effects were not dependent on the presence of a marker gene or the insertion of a second resistance gene. Positional effects of gene insertion influenced aphid performance on certain GM events. However, aphid fitness varied considerably more between conventional potato varieties than between Désirée and the GM events. Comparing different GM events to the non-transformed variety is relevant, since unintended effects of insertion can occur. Our protocols can be recommended for in planta risk assessments with aphids. Ecological perspective is gained by selecting several measured endpoints and by comparing the results with a baseline of conventional cultivars.
ABSTRACT
Induced plant defenses against either pathogens or herbivore attackers are regulated by phytohormones. These phytohormones are increasingly recognized as important mediators of interactions between organisms associated with plants. In this review, we discuss the role of plant defense hormones in sequential tri-partite interactions among plants, pathogenic microbes, and herbivorous insects, based on the most recent literature. We discuss the importance of pathogen trophic strategy in the interaction with herbivores that exhibit different feeding modes. Plant resistance mechanisms also affect plant quality in future interactions with attackers. We discuss exemplary evidence for the hypotheses that (i) biotrophic pathogens can facilitate chewing herbivores, unless plants exhibit effector-triggered immunity, but (ii) facilitate or inhibit phloem feeders. (iii) Necrotrophic pathogens, on the other hand, can inhibit both phloem feeders and chewers. We also propose herbivore feeding mode as predictor of effects on pathogens of different trophic strategies, providing evidence for the hypotheses that (iv) phloem feeders inhibit pathogen attack by increasing SA induction, whereas (v) chewing herbivores tend not to affect necrotrophic pathogens, while they may either inhibit or facilitate biotrophic pathogens. Putting these hypotheses to the test will increase our understanding of phytohormonal regulation of plant defense to sequential attack by plant pathogens and insect herbivores. This will provide valuable insight into plant-mediated ecological interactions among members of the plant-associated community.
