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Many parasites can interfere with their host’s defences tomaximize their fitness. Here, we investigated if there isheritable variation in the spider miteTetranychus evansifortraits associated with how they interact with their host plant.We also determined if this variation correlates with mitefecundity.Tetranychus evansican interfere with jasmonate (JA)defences which are the main determinant of anti-herbivoreimmunity in plants. We investigated (i) variation in fecundityin the presence and absence of JA defences, making use ofa wild-type tomato cultivar and a JA-deficient mutant(defenseless-1), and (ii) variation in the induction of JAdefences, in fourT. evansifield populations and 59 inbredlines created from an outbred population originating fromcontrolled crosses of the four field populations. We observed astrong positive genetic correlation between fecundity in thepresence (on wild-type) and the absence of JA defences (ondefenseless-1). However, fecundity did not correlate with themagnitude of induced JA defences in wild-type plants. Ourresults suggest that the performance of the specialistT. evansiis not related to their ability to manipulate plant defences,either because all lines can adequately reduce levels ofdefences, or because they are resistant to them.

Many parasites can interfere with their host's defences to maximize their fitness. Here, we investigated if there is a heritable variation in the spider mite, Tetranychus evansi for traits associated with how they interact with their host plant. We also determined if this variation correlates with mite fecundity. Tetranychus evansi can interfere with jasmonate (JA) defences which are the main determinant of anti-herbivore immunity in plants. We investigated (i) variation in fecundity in the presence and absence of JA defences, making use of a wild-type tomato cultivar and a JA-deficient mutant (defenseless-1), and (ii) variation in the induction of JA defences, in four T. evansi field populations and 59 inbred lines created from an outbred population originating from controlled crosses of the four-field populations. We observed a strong positive genetic correlation between fecundity in the presence (on WT) and the absence of JA defences (on def-1). However, fecundity did not correlate with the magnitude of induced JA defences in WT plants. Our results suggest that the performance of the specialist T. evansi is not related to their ability to manipulate plant defences, either because all lines can adequately reduce levels of defences, or because they are resistant to them.

Additional file 16: Figure S1. Chemical structures of the three products formed from funneling reactions utilized by microorganisms in the breakdown of organic compounds. Catechol and protocatechuic acid degradation proceeds via the β-ketoadipate pathway while hydroxyquinol is formed from protocatechuate and degraded in an alternative pathway found in some bacteria and fungi.

Additional file 20: Figure S5.in situ localization of T. urticae DOG genes (TuDOG11 and TuDOG3). A DIG-labelled antisense probe was used for hybridization and the signal was developed using anti-DIG-AP and FastRed as substrate. The reaction product is visible as a red signal (the cuticle got red staining in both antisense and sense treatment so we consider that as false signals) while the spider mite body shows green auto fluorescence. Abbreviations: C, cuticle; PME, posterior midgut epithelium; PM, posterior midgut; V, ventriculus; VE, ventricular epithelium; Scale bars: 100 μm.

Additional file 4: File S3. Coverage plots of 17 T. urticae DOG genes and their surrounding regions in the genome of Tetranychus urticae. Gene models of DOG genes and their neighboring genes are depicted as follows: large and small orange boxes represent coding sequences and untranslated regions, respectively, whereas introns are shown as connecting lines between the boxes. (+) and (-) represent the forward and reverse strand, respectively. Underneath the gene models of TuDOG7, TuDOG10 and TuDOG11, the length and position of an amplicon obtained by PCR (Fig. S4) is indicated with a red line. Next, coverage plots of Illumina-reads (‘“Illu.’”) from adult T. urticae polyA selected RNA [13] and from genomic DNA sequencing of the EtoxR (‘“Etox’”) and London(‘“Lon’”) strain of T. urticae [13, 110] are shown below the gene models. The Illumina reads coverage plots are followed by a coverage plot of Sanger (‘“San.’”) reads from genomic DNA sequencing of the London strain [13] and by an alignment of these Sanger reads with the T. urticae genome of the London strain. Paired-end Sanger reads for which both reads are mapped in or extend nearby the indicated region are denoted by thin lines to show pair connections [13] (see [43], for mapping details).

Biological control is an important ecosystem service delivered by natural enemies. Together with breeding for plant defence, it constitutes one of the most promising alternatives to pesticides for controlling herbivores in sustainable crop production. Especially induced plant defences may be promising targets in plant breeding for resistance against arthropod pests. Because they are activated upon herbivore damage, costs are only incurred when defence is needed. Moreover, they can be more specific than constitutive defences. Nevertheless, inducible defence traits that are harming plant pest organisms may interfere with biological control agents, such as predators and parasitoids. Despite the vast fundamental knowledge on plant defence mechanisms and their effects on natural enemies, our understanding of the feasibility of combining biological control with induced plant defence in practice is relatively poor. In this review, we focus on arthropod pest control and present the most important features of biological control with natural enemies and of induced plant defence. Furthermore, we show potential synergies and conflicts among them and, finally, identify gaps and list opportunities for their combined use in crop protection. We suggest that breeders should focus on inducible resistance traits that are compatible with the natural enemies of arthropod pests, specifically traits that help communities of natural enemies to build up.