This study investigates behavioural responses of adult western flower thrips (Frankliniella occidentalis Pergande; Thysan., Thripidae) females to direct contact with repellent phenylpropanoid plant compounds (salicylaldehyde and methyl salicylate) applied on bean and cucumber leaves. The residence time of F. occidentalis females until take off was significantly shorter on bean or cucumber leaf discs treated with salicylaldehyde at 1% concentration compared with control leaf discs. A methyl salicylate (1%) treatment of cucumber resulted in shorter time periods until thrips took off the treated leaf discs compared with the control leaf discs. In a choice experiment thrips avoided to settle on a 1% salicylaldehyde treatment of bean and cucumber leaf discs for a maximum of 3 h, on a 1% methyl salicylate treatment for a 5-h period. Within a 24-h period neither the egg-laying nor the feeding activity of F. occidentalis was affected after salicylaldehyde application (0.1%, 1%) on bean or cucumber. In contrast, methyl salicylate (1%) applied on bean and cucumber significantly prevented thrips females from oviposition and reduced the percentage of damaged area caused by their feeding activity for 24 h. As olfactory repellent plant volatiles applied on crop plants may elicit diverse post-landing responses of F. occidentalis, short-and long-term effects should be considered when evaluating the factual applicability of secondary plant compounds in a successful thrips management strategy.
A series of observational bioassays were conducted to investigate the behavioural responses of the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), to an application of a secondary plant compound to two different host plants with dissimilar leaf surface characteristics. Eugenol, a phenylpropanoid compound known to deter feeding and oviposition of the onion thrips, was applied to leek (Allium porrum L.) and cucumber (Cucumis sativus L.) at 1% concentration. Using a video system and special software for computing observational data, influences of this plant compound on the behaviour of T. tabaci females were evaluated. Eugenol treatment significantly prolonged the time periods thrips spent being inactive and moving across the treated leek or cucumber surface. The feeding periods on leek leaves treated with eugenol were clearly shorter compared to periods on untreated leek. The behaviours related to oviposition on leaves from both host species treated with eugenol were slightly reduced. T. tabaci females avoided direct contact with eugenol particularly when applied to leek, showing significantly lower contact duration compared to an untreated surface. This shows that behaviourmodifying secondary compounds such as eugenol may be used in various strategies and may contribute to the enhancement of current biological control measures and/or form novel components of Integrated Pest Management strategies.
Reduced representation library approaches are still a valuable tool for breeding and population and ecological genomics, even with impressive increases in sequencing capacity in recent years. Unfortunately, current approaches only allow for multiplexing up to 384 samples. To take advantage of increased sequencing capacity, we present Multi-GBS, a massively multiplexable extension to Genotyping-by-Sequencing that is also optimized for large conifer genomes. In Norway Spruce, a highly repetitive 20Gbp diploid genome with high population genetic variation, we call over a million variants in 32 genotypes from three populations, two natural forest in the Alps and Bohemian Alps, and a managed population from southeastern Austria using the existing TASSEL GBSv2 pipeline. Metric MDS analysis of replicated genotypes shows that technical bias in resulting genotype calling is minimal and that populations cluster in biologically meaningful ways.
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