A very long chain fatty acid responsive transcription factor, MYB93, regulates lateral root development in Arabidopsis.

Lateral roots (LRs) are critical to root system architecture development in plants. Although the molecular mechanisms by which auxin regulates LR development have been extensively studied, several additional regulatory systems are hypothesized to be involved. Recently, the regulatory role of very long chain fatty acids (VLCFAs) has been shown in LR development. Our analysis showed that LTPG1 and LTPG2, transporters of VLCFAs, are specifically expressed in the developing LR primordium (LRP), while the number of LRs is reduced in the ltpg1/ltpg2 double mutant. Moreover, late LRP development was hindered when the VLCFA levels were reduced by the VLCFA synthesis enzyme mutant, kcs1-5. However, the details of the regulatory mechanisms of LR development controlled by VLCFAs remain unknown. In this study, we propose a novel method to analyze the LRP development stages with high temporal resolution using a deep neural network and identify a VLCFA-responsive transcription factor, MYB93, via transcriptome analysis of kcs1-5. MYB93 showed a carbon chain length-specific expression response following treatment of VLCFAs. Furthermore, myb93 transcriptome analysis suggested that MYB93 regulated the expression of cell wall organization genes. In addition, we also found that LTPG1 and LTPG2 are involved in LR development through the formation of root cap cuticle, which is different from transcriptional regulation by VLCFAs. Our results suggest that VLCFA is a regulator of LRP development through transcription factor-mediated regulation of gene expression and the transportation of VLCFAs is also involved in LR development through root cap cuticle formation.

CRISPR/Cas9-mediated disruption of ALLENE OXIDE SYNTHASE results in defective 12-oxo-phytodienoic acid accumulation and reduced defense against spider mite (Tetranychus urticae) in liverwort (Marchantia polymorpha).

Allene oxide synthase (AOS) is a key enzyme involved in the biosynthesis of 12-oxo-phytodienoic acid (OPDA) and jasmonic acid and plays an important role in plant defense against herbivore attacks. In the liverwort, Marchantia polymorpha, we previously identified cytosol-type MpAOS1 and chloroplast-type MpAOS2 that show AOS activities. However, there is no direct evidence to show the subcellular localization of MpAOSs and their contribution to plant defense via OPDA production in M. polymorpha. In this study, we generated M. polymorpha mutants, with the MpAOS1 and MpAOS2 genes disrupted via CRISPR/Cas9-mediated genome editing; the loss of OPDA production was analyzed in double-knockout mutants. On AOS mutants, the survival rate and oviposition of spider mites (Tetranychus urticae) increased relative to those on wild-type plants. Overall, these findings suggest that defense systems via OPDA-signaling pathways in response to spider mites have been established in M. polymorpha.

Aerial (+)-borneol modulates root morphology, auxin signalling and meristematic activity in Arabidopsis roots.

One of the characteristic aspects of odour sensing in humans is the activation of olfactory receptors in a slightly different manner in response to different enantiomers. Here, we focused on whether plants showed enantiomer-specific response similar to that in humans. We exposed Arabidopsis seedlings to methanol (control) and (+)- or (-)-borneol, and found that only (+)-borneol reduced the root length. Furthermore, the root-tip width was more increased upon (+)-borneol exposure than upon (-)-borneol exposure. In addition, root-hair formation was observed near the root tip in response to (+)-borneol. Auxin signalling was strongly reduced in the root tip following exposure to (+)-borneol, but was detected following exposure to (-)-borneol and methanol. Similarly, in the root tip, the activity of cyclin B1:1 was detected on exposure to (-)-borneol and methanol, but not on exposure to (+)-borneol, indicating that (+)-borneol inhibits the meristematic activity in the root. These results partially explain the (+)-borneol-specific reduction in the root length of Arabidopsis. Our results indicate the presence of a sensing system specific for (+)-borneol in Arabidopsis.

Administration of Aspergillus oryzae suppresses DSS-induced colitis.

Aspergillus oryzae, a filamentous fungus, has long been used for the production of traditional Japanese foods. Here, we analyzed how A. oryzae administration affects the intestinal environment in mice. The results of 16S rRNA gene sequencing of the gut microbiota indicated that after the administration of heat-killed A. oryzae spores, the relative abundance of an anti-inflammatory Bifidobacterium pseudolongum strain became 2.0-fold greater than that of the control. Next, we examined the effect of A. oryzae spore administration on the development of colitis induced by dextran sodium sulfate in mice; we found that colitis was alleviated by not only heat-killed A. oryzae spores, but also the cell wall extracted from the spores. Our findings suggest that A. oryzae holds considerable potential for commercial application in the production of both traditional Japanese fermented foods and new foods with prebiotic functions.

Effects of Prohydrojasmon on the Number of Infesting Herbivores and Biomass of Field-Grown Japanese Radish Plants.

Prohydrojasmon (PDJ), an analog of jasmonic acid (JA), was found to induce direct and indirect defenses against herbivores in non-infested plants. To test whether PDJ can be used for pest control in crop production, we conducted experiments in pesticide-free Japanese radish fields from October 4 to December 12 in 2015. Twenty-four Japanese radish plants in three plots were treated with a 100 times-diluted commercial formulation (5%) of PDJ (treated plants), and 24 plants in three different plots were treated with water (control plants) until November 29 every week. Throughout the observation period, the number of aphids, leaf-mining fly larvae, vegetable weevils, and thrips was significantly lower on the treated plants than on the control plants. In contrast, the number of lepidopteran larvae was not significantly different between the treated and control plants throughout the study period. Parasitized aphids (mummies) were also observed in both plots. Poisson regression analyses showed that a significantly higher number of mummies was recorded on the treated plants as compared to that on the control plants when the number of aphids increased. This suggested that PDJ application to Japanese radish plants attracted more parasitoid wasps on the treated plants than on the control plants. We also identified eight terpenoids and methyl salicylate as the PDJ-induced plant volatiles in the headspace of the treated plants. Some of these volatiles might be responsible for attracting aphid-parasitoid wasps in the field. However, for other insect pests, we did not find any natural enemies. Interestingly, the genes of the JA and salicylic acid signaling pathways were differentially upregulated in the treated plants. We also observed that the PDJ treatments induced the expression of the genes related to glucosinolate biosynthesis and the subsequent isothiocyanate formation. Additionally, the weights of both the aboveground and belowground parts of the treated plants were significantly lower than those of the respective parts of the control plants. These results indicated that the treatment of Japanese radish plants with a 100 times-diluted commercial formulation of PDJ induced their direct and indirect defenses against several insect pest species to reduce their numbers, and negatively affected their biomass.

Field-Grown Rice Plants Become More Productive When Exposed to Artificially Damaged Weed Volatiles at the Seedling Stage.

It is known that undamaged plants that have been exposed to volatiles from damaged con- or heterospecific plants become more resistant against herbivores. This is one of the plants' induced resistant responses against herbivores. To test whether this response can be used for rice production, we conducted the following experiments over 2 years (2012 and 2013). Rice seedlings were first planted in the rice seedling bed for 2 weeks in early May. There, half of the rice seedlings were exposed to artificially damaged weed volatiles three times for 12 days (treated plants). Weeds were randomly collected from the areas that were >100 m away from the seedling bed and the rice paddy fields. The remaining seedlings were not exposed (control plants). In the middle of May, bunches (ca. three seedlings per bunch) were transplanted to the rice paddy field. In July, leaf damage was observed. The total number of leaves in the treated and control plants was not significantly different. In contrast, the total number of damaged leaves in the treated plants was significantly lower than that in the control plants. In September, rice grains were harvested. The average weight of a rice grain from the treated and control plants was not significantly different. However, the weight of grains per bunch of treated plants was significantly higher than that of control plants; this indicated a significant increase of the number of grains by 23% in 2012 and by 18% in 2013 in the treated plants compared to that in the control plants. The volatiles emitted from the weeds included monoterpenoids (40.4% in total), green leaf volatiles (46.5%), short-chain alcohols (5.3%), short-chain ketone (5.4%), short-chain acetate (0.5%), short-chain aldehyde (1.1%), and hydrocarbon (0.7%). These results suggest that exposure of volatiles from artificially damaged weeds to rice seedlings has the potential to increase rice production.

Suppressed Methionine γ-Lyase Expression Causes Hyperaccumulation of S-Methylmethionine in Soybean Seeds.

Several soybean (Glycine max) germplasms, such as Nishiyamahitashi 98-5 (NH), have an intense seaweed-like flavor after cooking because of their high seed S-methylmethionine (SMM) content. In this study, we compared the amounts of amino acids in the phloem sap, leaves, pods, and seeds between NH and the common soybean cultivar Fukuyutaka. This revealed a comparably higher SMM content alongside a higher free Met content in NH seeds, suggesting that the SMM-hyperaccumulation phenotype of NH soybean was related to Met metabolism in seeds. To investigate the molecular mechanism behind SMM hyperaccumulation, we examined the phenotype-associated gene locus in NH plants. Analyses of the quantitative trait loci in segregated offspring of the cross between NH and the common soybean cultivar Williams 82 indicated that one locus on chromosome 10 explains 71.4% of SMM hyperaccumulation. Subsequent fine-mapping revealed that a transposon insertion into the intron of a gene, Glyma.10g172700, is associated with the SMM-hyperaccumulation phenotype. The Glyma.10g172700-encoded recombinant protein showed Met-γ-lyase (MGL) activity in vitro, and the transposon-insertion mutation in NH efficiently suppressed Glyma.10g172700 expression in developing seeds. Exogenous administration of Met to sections of developing soybean seeds resulted in transient increases in Met levels, followed by continuous increases in SMM concentrations, which was likely caused by Met methyltransferase activity in the seeds. Accordingly, we propose that the SMM-hyperaccumulation phenotype is caused by suppressed MGL expression in developing soybean seeds, resulting in transient accumulation of Met, which is converted into SMM to avoid the harmful effects caused by excess free Met.

Targeting diamondback moths in greenhouses by attracting specific native parasitoids with herbivory-induced plant volatiles.

We investigated the recruitment of specific parasitoids using a specific blend of synthetic herbivory-induced plant volatiles (HIPVs) as a novel method of pest control in greenhouses. In the Miyama rural area in Kyoto, Japan, diamondback moth (DBM) (Plutella xylostella, Lepidoptera: Plutellidae) larvae are an important pest of cruciferous crops in greenhouses, and Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of DBM, is found in the surrounding areas. Dispensers of HIPVs that attracted C. vestalis and honey feeders were set inside greenhouses (treated greenhouses). The monthly incidence of DBMs in the treated greenhouses was significantly lower than that in the untreated greenhouses over a 2-year period. The monthly incidences of C. vestalis and DBMs were not significantly different in the untreated greenhouses, whereas monthly C. vestalis incidence was significantly higher than monthly DBM incidence in the treated greenhouses. Poisson regression analyses showed that, in both years, a significantly higher number of C. vestalis was recorded in the treated greenhouses than in the untreated greenhouses when the number of DBM adults increased. We concluded that DBMs were suppressed more effectively by C. vestalis in the treated greenhouses than in the untreated greenhouses.

Synchronous Occurrences of the Diamondback Moth (Lepidoptera: Plutellidae) and its Parasitoid Wasp Cotesia vestalis (Hymenoptera: Braconidae) in Greenhouses in a Satoyama Area.

We characterized the correlation between the occurrences of diamondback moth, Plutella xylostella (L.), larvae and their dominant native parasitoid wasp, Cotesia vestalis (Haliday), in commercial greenhouses in a satoyama area, called Miyama, in Kyoto, Japan. In the three greenhouses used in this study, cruciferous 'mizuna' (Brassica rapa var. laciniifolia [Brassicales: Brassicaceae]) crops were grown. Pesticides against diamondback moth were not routinely applied in the greenhouses. We confirmed that populations of diamondback moth and C. vestalis were maintained on the wild crucifer plant Rorippa indica in the surrounding area from March to December. In the greenhouses, we observed several occurrences of diamondback moth larvae that were, in most cases, followed by occurrences of C. vestalis. We found that C. vestalis females were attracted by volatiles emitted from mizuna plants that were lightly infested with second-stadium diamondback moth larvae under laboratory conditions. The synchronous appearance of diamondback moth larvae and C. vestalis could be explained by the latter being attracted by the volatiles emitted from mizuna plants infested by diamondback moth larvae in the greenhouses.

Oviposition Experience of Parasitoid Wasps with Nonhost Larvae Affects their Olfactory and Contact-Behavioral Responses toward Host- and Nonhost-Infested Plants.

In nature, parasitoid wasps encounter and sometimes show oviposition behavior to nonhost species. However, little is known about the effect of such negative incidences on their subsequent host-searching behavior. We tested this effect in a tritrophic system of maize plants (Zea mays), common armyworms (hosts), tobacco cutworms (nonhosts), and parasitoid wasps, Cotesia kariyai. We used oviposition inexperienced C. kariyai and negative-experienced individuals that had expressed oviposition behavior toward nonhosts on nonhost-infested maize leaves. We first observed the olfactory behavior of C. kariyai to volatiles from host-infested plants or nonhost-infested plants in a wind tunnel. Negative-experienced wasps showed significantly lower rates of taking-off behavior (Step-1), significantly longer duration until landing (Step-2), and lower rates of landing behavior (Step-3) toward nonhost-infested plants than inexperienced wasps. However, the negative-experience did not affect these three steps toward host-infested plants. A negative experience appears to have negatively affected the olfactory responses to nonhost-infested plants. The chemical analyses suggested that the wasps associated (Z)-3-hexenyl acetate, a compound that was emitted more in nonhost-infested plants, with the negative experience, and reduced their response to nonhost-infested plants. Furthermore, we observed that the searching duration of wasps on either nonhost- or host-infested plants (Step-4) was reduced on both plant types after the negative experiences. Therefore, the negative experience in Step-4 would be nonadaptive for wasps on host-infested plants. Our study indicated that the density (i.e., possible encounters) of nonhost species as well as that of host species in the field should be considered when assessing the host-searching behavior of parasitoid wasps.

Silkworms suppress the release of green leaf volatiles by mulberry leaves with an enzyme from their spinnerets.

In response to herbivory, plants emit a blend of volatile organic compounds that includes green leaf volatiles (GLVs) and terpenoids. These volatiles are known to attract natural enemies of herbivores and are therefore considered to function as an indirect defense. Selection should favor herbivores that are able to suppress these volatile emissions, and thereby make themselves less conspicuous to natural enemies. We tested this possibility for silkworms, which were observed to leave secretions from their spinnerets while feeding on mulberry leaves. When we ablated the spinnerets of silkworms, no secretions were observed. Leaves infested by intact silkworms released smaller amounts of GLVs than leaves infested by ablated silkworms, indicating that the spinneret secretion suppressed GLV production. This difference in GLV emissions was also reflected in the behavioral response of Zenillia dolosa (Tachinidae), a parasitoid fly of silkworms. The flies laid fewer eggs when exposed to the volatiles from intact silkworm-infested leaves than when exposed to the volatiles from ablated silkworm-infested leaves. We identified a novel enzyme in the secretion from the spinneret that is responsible for the GLV suppression. The enzyme converted 13(S)-hydroperoxy-(9Z,11E,15Z)-octadecatrienoic acid, an intermediate in the biosynthetic pathway of GLVs, into its keto-derivative in a stereospecific manner. Taken together, this study shows that silkworms are able to feed on mulberry in a stealthy manner by suppressing GLV production with an enzyme in secretions of their spinnerets, which might be a countermeasure against induced indirect defense by mulberry plants.

Parasitoid wasps' exposure to host-infested plant volatiles affects their olfactory cognition of host-infested plants.

Using Cotesia vestalis, a parasitoid wasp of diamondback moth larvae and three crucifer plant species (cabbage, komatsuna, and Japanese radish), we examined the effects of exposure to host-infested plant volatiles from one plant species on a newly emerged wasp's subsequent olfactory cognition of host-infested plant volatiles from the same or different plant species. The preference of C. vestalis between infested and uninfested plant volatiles was tested in a choice chamber. Volatile-inexperienced wasps significantly preferred infested cabbage and infested radish volatiles, but not infested komatsuna volatiles. After exposure to infested cabbage volatiles, wasps showed a significant preference for infested cabbage volatiles, while the significant preference for infested radish volatiles that had been observed in inexperienced wasps was no longer observed. After exposure to infested komatsuna volatiles, wasps significantly preferred infested komatsuna volatiles, and the pre-exposure significant preferences for infested cabbage volatiles and infested radish volatiles remained. After exposure to infested radish volatiles, the significant preferences for infested cabbage and infested radish volatiles did not change. Furthermore, wasps showed a significant preference for infested komatsuna volatiles. The compound compositions of the volatile blends from the three infested plant species were grouped separately in a principal coordinates analysis. The experience-based cognition of C. vestalis for host-infested plant volatiles of three plant species is discussed.

Weeding volatiles reduce leaf and seed damage to field-grown soybeans and increase seed isoflavones.

Field experiments were conducted over 3 years (2012, 2013, and 2015), in which half of the young stage soybean plants were exposed to volatiles from cut goldenrods three times over 2-3 weeks, while the other half remained unexposed. There was a significant reduction in the level of the total leaf damage on exposed soybean plants compared with unexposed ones. In 2015, the proportion of damage to plants by Spodoptera litura larvae, a dominant herbivore, was significantly less in the exposed field plots than in the unexposed plots. Under laboratory conditions, cut goldenrod volatiles induced the direct defenses of soybean plants against S. litura larvae and at least three major compounds, α-pinene, ß-myrcene, and limonene, of cut goldenrod volatiles were involved in the induction. The number of undamaged seeds from the exposed plants was significantly higher than that from unexposed ones. Concentrations of isoflavones in the seeds were significantly higher in seeds from the exposed plants than in those from the unexposed plants. Future research evaluating the utility of weeding volatiles, as a form of plant-plant communications, in pest management programs is necessary.

Intake and transformation to a glycoside of (Z)-3-hexenol from infested neighbors reveals a mode of plant odor reception and defense.

Plants receive volatile compounds emitted by neighboring plants that are infested by herbivores, and consequently the receiver plants begin to defend against forthcoming herbivory. However, to date, how plants receive volatiles and, consequently, how they fortify their defenses, is largely unknown. In this study, we found that undamaged tomato plants exposed to volatiles emitted by conspecifics infested with common cutworms (exposed plants) became more defensive against the larvae than those exposed to volatiles from uninfested conspecifics (control plants) in a constant airflow system under laboratory conditions. Comprehensive metabolite analyses showed that only the amount of (Z)-3-hexenylvicianoside (HexVic) was higher in exposed than control plants. This compound negatively affected the performance of common cutworms when added to an artificial diet. The aglycon of HexVic, (Z)-3-hexenol, was obtained from neighboring infested plants via the air. The amount of jasmonates (JAs) was not higher in exposed plants, and HexVic biosynthesis was independent of JA signaling. The use of (Z)-3-hexenol from neighboring damaged conspecifics for HexVic biosynthesis in exposed plants was also observed in an experimental field, indicating that (Z)-3-hexenol intake occurred even under fluctuating environmental conditions. Specific use of airborne (Z)-3-hexenol to form HexVic in undamaged tomato plants reveals a previously unidentified mechanism of plant defense.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

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.

Effects of time after last herbivory on the attraction of corn plants infested with common arymworms to a parasitic wasp Cotesia kariyai.

Females of the gregarious endoparasitoid Cotesia kariyai were attracted to a blend of volatiles released from corn plants infested with larvae of their host, the common armyworm (Mythimna separata). We investigated the effects of time after the last infestation (1-168 h) on the attractiveness of corn plants infested by host larvae by using a wind tunnel under laboratory conditions. Immediately after the removal of the larvae, parasitoids were attracted more to plants that had been infested with the larvae than to intact plants (control). This attractiveness gradually decreased with time after the last infestation. The attractiveness of the infested plants was significantly higher than that of intact plants when the time after the last infestation was within 1 day. Fifteen herbivore-induced volatiles were recorded in the headspace of infested corn plants irrespective of time. The amounts of some compounds including (Z)-3-hexen-1-yl acetate, which have already been reported to attract C. kariyai, correlated with the attractiveness. The ecological meaning of the duration of production of C. kariyai attractants is discussed.

Herbivore-specific, density-dependent induction of plant volatiles: honest or "cry wolf" signals?

Plants release volatile chemicals upon attack by herbivorous arthropods. They do so commonly in a dose-dependent manner: the more herbivores, the more volatiles released. The volatiles attract predatory arthropods and the amount determines the probability of predator response. We show that seedlings of a cabbage variety (Brassica oleracea var. capitata, cv Shikidori) also show such a response to the density of cabbage white (Pieris rapae) larvae and attract more (naive) parasitoids (Cotesia glomerata) when there are more herbivores on the plant. However, when attacked by diamondback moth (Plutella xylostella) larvae, seedlings of the same variety (cv Shikidori) release volatiles, the total amount of which is high and constant and thus independent of caterpillar density, and naive parasitoids (Cotesia vestalis) of diamondback moth larvae fail to discriminate herbivore-rich from herbivore-poor plants. In contrast, seedlings of another cabbage variety of B. oleracea (var. acephala: kale) respond in a dose-dependent manner to the density of diamondback moth larvae and attract more parasitoids when there are more herbivores. Assuming these responses of the cabbage cultivars reflect behaviour of at least some genotypes of wild plants, we provide arguments why the behaviour of kale (B. oleracea var acephala) is best interpreted as an honest signaling strategy and that of cabbage cv Shikidori (B. oleracea var capitata) as a "cry wolf" signaling strategy, implying a conflict of interest between the plant and the enemies of its herbivores: the plant profits from being visited by the herbivore's enemies, but the latter would be better off by visiting other plants with more herbivores. If so, evolutionary theory on alarm signaling predicts consequences of major interest to students of plant protection, tritrophic systems and communication alike.

Predation-related odours reduce oviposition in a herbivorous mite.

When adult females of the herbivorous mite, Tetranychus urticae, were exposed to the predatory mite, Phytoseiulus persimilis, they laid fewer eggs than females that had not been exposed to P. persimilis when transferred onto a new leaf patch. However, when T. urticae females were exposed to either products of P. persimilis or artificially damaged conspecific eggs on a leaf patch, the number of T. urticae eggs on a new leaf patch did not differ significantly from the control. The reduced oviposition was neither due to the feeding activity on the leaf patch with P. persimilis nor to that on the new leaf patch. There was also no significant difference between the number of T. urticae eggs produced on a new leaf patch following exposure to the odours of a neighbouring leaf patch where there had previously been either P. persimilis or T. urticae adults. However, female T. urticae that had been exposed to odours from neighbouring leaf patches on which both T. urticae and P. persimilis had been placed produced significantly fewer eggs on a new leaf patch than those that had not been exposed to such odours. Neither odours from neighbouring intact leaf patches on which T. urticae eggs were preyed on by P. persimilis, nor odours from a neighbouring Parafilm patch on which T. urticae was preyed on by P. persimilis affected the oviposition of T. urticae. These data suggest that the presence of T. urticae, P. persimilis and a leaf patch are needed for the emission of odours to reduce oviposition in T. urticae.

Intraspecies variation in the Kanzawa spider mite differentially affects induced defensive response in lima bean plants.

The Kanzawa spider mite, Tetranychus kanzawai, is a polyphagous herbivore that feeds on various plant families, including the Leguminacae. Scars made by the mite on lima bean leaves (Phaseolus lunatus) were classified into two types: white and red. We obtained two strains of mites--"White" and "Red"--by selecting individual mites based on the color of the scars. Damage made by the Red strain induced the expression of genes for both basic chitinase, which was downstream of the jasmonic acid (JA) signaling pathway, and acidic chitinase, which was downstream of the salicylic acid (SA) signaling pathway. White strain mites also induced the expression of the basic chitinase gene in infested leaves but they only slightly induced the acidic chitinase gene. The Red genotype was dominant over the White for the induction of the acidic chitinase gene. The amount of endogenous salicylates in leaves increased significantly when infested by Red strain mites but did not increase when infested by White strain mites. JA and SA are known to be involved in the production of lima bean leaf volatiles induced by T. urticae. The blend of volatiles emitted from leaves infested by the Red strain were qualitatively different from those infested by the White strain, suggesting that the SA and JA signaling pathways are differently involved in the production of lima bean leaf volatiles induced by T. kanzawai of different strains.