Egg Laying of Cabbage White Butterfly (Pieris brassicae) on Arabidopsis thaliana Affects Subsequent Performance of the Larvae

Plant resistance to the feeding by herbivorous insects has recently been found to be positively or negatively influenced by prior egg deposition. Here we show how crucial it is to conduct experiments on plant responses to herbivory under conditions that simulate natural insect behaviour. We used a well- studied plant – herbivore system, Arabidopsis thaliana and the cabbage white butterfly Pieris brassicae, testing the effects of naturally laid eggs (rather than egg extracts) and allowing larvae to feed gregariously as they do naturally (rather than placing single larvae on plants). Under natural conditions, newly hatched larvae start feeding on their egg shells before they consume leaf tissue, but access to egg shells had no effect on subsequent larval performance in our experiments. However, young larvae feeding gregariously on leaves previously laden with eggs caused less feeding damage, gained less weight during the first 2 days, and suffered twice as high a mortality until pupation compared to larvae feeding on plants that had never had eggs. The concentration of the major anti-herbivore defences of A. thaliana, the glucosinolates, was not significantly increased by oviposition, but the amount of the most abundant member of this class, 4-methylsulfinylbutyl glucosinolate was 1.8-fold lower in larval-damaged leaves with prior egg deposition compared to damaged leaves that had never had eggs. There were also few significant changes in the transcript levels of glucosinolate metabolic genes, except that egg deposition suppressed the feeding-induced up-regulation of FMOGS-OX2, a gene encoding a flavin monooxygenase involved in the last step of 4-methylsulfinylbutyl glucosinolate biosynthesis. Hence, our study demonstrates that oviposition does increase A. thaliana resistance to feeding by subsequently hatching larvae, but this cannot be attributed simply to changes in glucosinolate content

シゼン ノ ヤナギ グンシュウ ニ オケル ショクブツ キハツセイ ブッシツ ガ バイカイスル ショクブツ - コンチュウ ソウゴ サヨウ ノ トクイセイ

京都大学0048新制・課程博士博士(理学)甲第14440号理博第3437号新制||理||1504(附属図書館)UT51-2009-D152京都大学大学院理学研究科生物科学専攻(主査)教授 髙林 純示, 教授 工藤 洋, 教授 戸部 博学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

An apparent trade-off between direct and signal-based induced indirect defence against herbivores in willow trees.

Signal-based induced indirect defence refers to herbivore-induced production of plant volatiles that attract carnivorous natural enemies of herbivores. Relationships between direct and indirect defence strategies were studied using tritrophic systems consisting of six sympatric willow species, willow leaf beetles (Plagiodera versicolora), and their natural predators, ladybeetles (Aiolocaria hexaspilota). Relative preferences of ladybeetles for prey-infested willow plant volatiles, indicating levels of signal-based induced indirect defence, were positively correlated with the vulnerability of willow species to leaf beetles, assigned as relative levels of direct defence. This correlation suggested a possible trade-off among the species, in terms of resource limitation between direct defence and signal-based induced indirect defence. However, analyses of volatiles from infested and uninfested plants showed that the specificity of infested volatile blends (an important factor determining the costs of signal-based induced indirect defence) did not affect the attractiveness of infested plant volatiles. Thus, the suggested trade-off in resource limitation was unlikely. Rather, principal coordinates analysis showed that this 'apparent trade-off' between direct and signal-based induced indirect defence was partially explained by differential preferences of ladybeetles to infested plant volatiles of the six willow species. We also showed that relative preferences of ladybeetles for prey-infested willow plant volatiles were positively correlated with oviposition preferences of leaf beetles and with the distributions of leaf beetles in the field. These correlations suggest that ladybeetles use the specificity of infested willow plant volatiles to find suitable prey patches

Non-destructive collection and metabarcoding of arthropod environmental DNA remained on a terrestrial plant

Abstract Reliable survey of arthropods is a crucial for their conservation, community ecology, and pest control on terrestrial plants. However, efficient and comprehensive surveys are hindered by challenges in collecting arthropods and identifying especially small species. To address this issue, we developed a non-destructive environmental DNA (eDNA) collection method termed “plant flow collection” to apply eDNA metabarcoding to terrestrial arthropods. This involves spraying distilled or tap water, or using rainfall, which eventually flows over the surface of the plant, and is collected in a container that is set at the plant base. DNA is extracted from collected water and a DNA barcode region of cytochrome c oxidase subunit I (COI) gene is amplified and sequenced using a high-throughput Illumina Miseq platform. We identified more than 64 taxonomic groups of arthropods at the family level, of which 7 were visually observed or artificially introduced species, whereas the other 57 groups of arthropods, including 22 species, were not observed in the visual survey. These results show that the developed method is possible to detect the arthropod eDNA remained on plants although our sample size was small and the sequence size was unevenly distributed among the three water types tested

The Use of Synthetic Herbivory-Induced Plant Volatiles That Attract Specialist Parasitoid Wasps, Cotesia vestalis, for Controlling the Incidence of Diamondback Moth Larvae in Open Agricultural Fields

<jats:p>We evaluated the effectiveness of using a blend of volatiles that attract <jats:italic>Cotesia vestalis</jats:italic>, a specialist parasitoid wasp of diamondback moth (DBM) larvae, to control DBM larvae on cabbage plants under open field conditions. We set three dispensers of the synthetic <jats:italic>C. vestalis</jats:italic> attractant together with one sugary-food feeder in a cabbage plot (10 m × 1 m; the treated plot) on one side of a pesticide-free open agricultural field (approximately 20 m × 20 m) from June to September in 2010 and July to August in 2011. On the other side of the field, we created a control cabbage plot of the same size in which neither dispensers nor a feeder was set. The incidences of DBM larvae and <jats:italic>C. vestalis</jats:italic> cocoons in the control and treated plots were compared. In 2010, the incidence of DBM larvae in the treated plot was significantly lower than that in the control plot. Poisson regression analyses in 2010 showed that the rate of increase in the number of <jats:italic>C. vestalis</jats:italic> cocoons along with an increase in the number of DBM larvae in the treated plot was significantly higher than that in the control plot. In 2011, the incidence in both the treated and control plots remained low (five larvae per plant or less) with no significant difference between the plots. Poisson regression analyses in 2011 showed that the number of <jats:italic>C. vestalis</jats:italic> cocoons in the treated plot was significantly higher than that in the control plot, irrespective of the number of DBM larvae. This 2-year field study suggested that the dispensers recruited native <jats:italic>C. vestalis</jats:italic> from the surrounding environment to the treated plot, and the dispensers controlled the number of DBM larvae in 2010 when the density of DBM larvae exceeded the economic injury levels for the cabbage crop. We also compared the incidences of other arthropods in the control and treated plots. The incidences of <jats:italic>Pieris rapae</jats:italic> larvae and Plusiinae spp. were not affected by the treatments. The number of aphids in the treated and control plots was inconsistent between the 2 years. Based on these 2-year results, the possible use of <jats:italic>C. vestalis</jats:italic> attractants in open agricultural fields is discussed.</jats:p&gt

Relationship between vulnerability of willow plants and preferences of ladybeetles to willow plant volatiles.

<p>Leaf areas damaged by five larvae of leaf beetle <i>Plagiodera versicolora</i> until pupation was defined as an index of vulnerability of willow plants (mean ± S.E., N = 10). The relative residence time of predatory ladybeetles <i>Aiolocaria hexaspilota</i>, attracted by willow plant volatiles was defined as an index of the preferences of the ladybeetles (mean ± S.E., N = 30). Odour source: (A) infested plants and (B) uninfested plants. Erio: <i>Salix eriocarpa</i>; Chae: <i>S. chaenomeloides</i>; Inte: <i>S. integra</i>; Miya: <i>S. miyabeana</i>; Jess: <i>S. jessoensis</i>; Grac: <i>S. gracilistyla</i> and Tria: <i>S. triandra</i>.</p

Degree of specificity of infested plant volatiles and preferences of ladybeetles to willow plant volatiles.

<p>The degree of specificity of infested-plant volatiles compared with uninfested-plant volatiles was indicated by the dissimilarity distances between volatiles from uninfested and infested plants within a plant species. The relative residence time of predatory ladybeetles <i>Aiolocaria hexaspilota</i>, attracted by willow plant volatiles was defined as an index of the preferences of the ladybeetles. Erio: <i>Salix eriocarpa</i>; Chae: <i>S. chaenomeloides</i>; Inte: <i>S. integra</i>; Miya: <i>S. miyabeana</i>; Jess: <i>S. jessoensis</i>; Grac: <i>S. gracilistyla</i> and Tria: <i>S. triandra</i>.</p

Principal coordinates analysis on volatiles composition of willow plant species.

<p>(A) Plots of axes 1 and 2 (shown in panels b and c) of the principal coordinates analysis of 28 samples based on volatiles composition (▪, <i>Salix chaenomeloides</i>; □, <i>S. eriocarpa</i>; ○, <i>Salix integra</i>; •, <i>S. miyabeana</i>; Δ, <i>S. jessoensis</i>; ▴, <i>S. gracilistyla</i>). The average score of each plant species is shown as a larger symbol. The first and second axes of the PCoA (Dim 1 and Dim 2) explained 30.4% and 27.6%, respectively, of the variation in association between samples, taking the absolute values of negative eigenvalues. (B and C) Relationships between the average scores of each plant species in the first (B) and second (C) axes of the PCoA and the relative residence times of predatory ladybeetles <i>Aiolocaria hexaspilota</i> attracted by infested plant volatiles. The scores (coordinates) of volatile compounds are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051505#pone.0051505.s004" target="_blank">Table S3</a>.</p

Relationship between oviposition preferences of leaf beetles and preferences of ladybeetles to willow plant volatiles.

<p>The number of eggs laid by leaf beetles <i>Plagiodera versicolora</i> was defined as an index of oviposition preferences of leaf beetles (mean ± S.E., N = 9). The relative residence time of predatory ladybeetles <i>Aiolocaria hexaspilota</i>, attracted by willow plant volatiles was defined as an index of the preferences of the ladybeetles (mean ± S.E., N = 30). Odour source: (A) infested plants and (B) uninfested plants. Erio: <i>S. eriocarpa</i>; Chae: <i>S. chaenomeloides</i>; Inte: <i>S. integra</i>; Miya: <i>S. miyabeana</i>; Jess: <i>S. jessoensis</i>; Grac: <i>S. gracilistyla</i> and Tria: <i>S. triandra</i>.</p