Native Host Plants Research Articles

Concordant population dynamics of Lepidoptera herbivores in a forest ecosystem

It is frequently assumed that population fluctuations are largely independent within a community of trophically-similar species, but this need not be so. If population fluctuations are partly synchronized or concordant, this will produce interannual variability in the community’s aggregate abundance and generate temporal variance in ecosystem structure. We studied the community of Lepidoptera inhabiting northern hardwood forests in New Hampshire, USA, to evaluate the hypothesis that fluctuations in consumer communities can arise from concordant dynamics of constituent populations. Interannual comparisons of moth abundances for � 75 species sampled at three sites over four years revealed that concordant dynamics contribute strongly to interannual variability in the abundance of consumers. A conspicuous decline in community abundance from 2004 to 2005 was the result of predominantly negative population growth rates of the component species, while an increase in community abundance from 2006 to 2007 was the result of predominantly positive population growth rates. Population dynamics most strongly linked species that feed in the early season (perhaps due to shared responses to climatic effects), but not species that might share natural enemies or host plants. The observed concordant dynamics introduced conspicuous temporal variation in the abundance of primary consumers relative to plants and secondary consumers, thereby altering the forest’s trophic structure. Such variance in the aggregate abundance of forest primary consumers could generate time-lagged fluctuations in abundances of secondary consumers and will generally have important consequences for ecosystem properties and processes that are nonlinear functions of consumer abundance, such as plant community structure and nutrient cycling.

Comparing Host Plant Resistance, Engineered Resistance, and Insecticide Treatment for Control of Colorado Potato Beetle and Potato Leafhopper in Potatoes

The Colorado potato beetle,Leptinotarsa decemlineata(Say) Order Coleoptera and the potato leafhopper,Empoasca fabae(Harris) Order Homoptera, are the major insect pests of potato in eastern North America. In two years of field trials, we compared the effectiveness of three pest management options for the control of Colorado potato beetle and potato leafhopper: natural host plant resistance (glandular trichomes), engineered resistance (Bacillus thuringiensis[Bt] Berlinercry3Agene) and a susceptible potato cultivar (Superior) with an at-planting application of the insecticide thiamethoxam. Similar and acceptable control of the Colorado potato beetle larvae was obtained with theBt-cry3Alines and the thiamethoxam treated “Superior” variety. The glandular trichome cultivar had significantly less Colorado potato beetle damage than did the untreated “Superior” in 2004, although damage was significantly greater than in theBt-cry3Alines and the insecticide-treated potatoes for both years, and was the only treatment that consistently had very little potato leafhopper damage. These data demonstrate that although each type of host plant resistance mechanism (Bt-cry3Aor glandular trichomes) was as effective as the chemical control against one of the insects, neither provides adequate resistance to both Colorado potato beetle and potato leaf hopper.

Response of the Vitis vinifera L. cv. ‘Nebbiolo’ proteome to Flavescence dorée phytoplasma infection

Flavescence dorée is a serious phytoplasma disease affecting grapevine in several European countries. We studied the interaction of Flavescence dorée phytoplasma with its natural plant host by monitoring the effects of infection on the protein expression profile. Among the 576 analyzed spots, 33 proteins were differentially regulated in infected grapevines. Grouping into MIPS functional categories showed proteins involved in metabolism (21%), energy processes (9%), protein synthesis (3%), protein fate (18%), cellular transport and transport routes (6%), cell defense and virulence (42%). Among the differentially regulated proteins, we selected six targets (thaumatin I, thaumatin II, osmotin-like protein, plant basic secretory protein, AAA(+) Rubisco activase and proteasome α5 subunit) and we analyzed their expression by quantitative RT-PCR on samples collected in 2008 and 2009 in several vineyards in Piedmont region, Italy. There was a positive correlation between mRNA and protein expression for most of the genes in both the years. We discuss the involvement of these proteins in the specific response to phytoplasma infection. To our knowledge, this work is the first to investigate the response of the grapevine proteome to Flavescence dorée phytoplasma infection, and provides reference protein profiles for future comparative proteomic and genomic studies.

Establishment of a self-propagating population of the African malaria vector Anopheles arabiensis under semi-field conditions

BackgroundThe successful control of insect disease vectors relies on a thorough understanding of their ecology and behaviour. However, knowledge of the ecology of many human disease vectors lags behind that of agricultural pests. This is partially due to the paucity of experimental tools for investigating their ecology under natural conditions without risk of exposure to disease. Assessment of vector life-history and demographic traits under natural conditions has also been hindered by the inherent difficulty of sampling these seasonally and temporally varying populations with the limited range of currently available tools. Consequently much of our knowledge of vector biology comes from studies of laboratory colonies, which may not accurately represent the genetic and behavioural diversity of natural populations. Contained semi-field systems (SFS) have been proposed as more appropriate tools for the study of vector ecology. SFS are relatively large, netting-enclosed, mesocosms in which vectors can fly freely, feed on natural plant and vertebrate host sources, and access realistic resting and oviposition sites.MethodsA self-replicating population of the malaria vector Anopheles arabiensis was established within a large field cage (21 × 9.1 × 7.1 m) at the Ifakara Health Institute, Tanzania that mimics the natural habitat features of the rural village environments where these vectors naturally occur. Offspring from wild females were used to establish this population whose life-history, behaviour and demography under semi-field conditions was monitored over 24 generations.ResultsThis study reports the first successful establishment and maintenance of an African malaria vector population under SFS conditions for multiple generations (> 24). The host-seeking behaviour, time from blood feeding to oviposition, larval development, adult resting and swarming behaviour exhibited by An. arabiensis under SFS conditions were similar to those seen in nature.ConclusionsThis study presents proof-of-principle that populations of important African malaria vectors can be established within environmentally realistic, contained semi-field settings. Such SFS will be valuable tools for the experimental study of vector ecology and assessment of their short-term ecological and longer-term evolutionary responses to existing and new vector control interventions.

The Asian black truffle Tuber indicum can form ectomycorrhizas with North American host plants and complete its life cycle in non-native soils

The Asian black truffle Tuber indicum is morphologically and phylogenetically similar to the European black truffle Tuber melanosporum. T. indicum is considered a threat to T. melanosporum trufficulture due to its presumed competitiveness and broad host compatibility. Recently, in independent events, T. indicum was found fruiting in a forest in Oregon, USA, and was detected as ectomycorrhizas within a truffle orchard established with trees believed to have been inoculated with T. melanosporum. We used haplotype networking to assess intraspecific ITS rDNA diversity among Asian and North American T. indicum group B isolates. To further assess the potential of T. indicum to spread onto native host plants it was inoculated onto seedlings of loblolly pine (Pinus taeda) and pecan (Carya illinoinensis, Juglandaceae), species endemic to North America. T. indicum formed ectomycorrhizas on both host species examined. This supports previous studies from Europe and Asia that indicate T. indicum has a broad host spectrum, an ecological trait that may be important to its invasion ecology. This is the first report of T. indicum introductions in North America and of this species fruiting outside of its native range. To help prevent further unintended truffle introductions we recommend that fruitbodies used by the truffle industry for inoculating seedlings first be identified with DNA methods.

Non‐native plants reduce abundance, richness, and host specialization in lepidopteran communities

The impact of non‐native plant invasions on ecosystems has been controversial because obvious local effects have not yet led to the global extinction of any native plant species on continents and large islands. We suggest that extinction is not the appropriate measure of impact on ecosystem function and present evidence that non‐native plant invasions or the replacement of native plants with non‐native ornamentals results in significant bottom‐up reductions of energy available for local food webs. Using replicated common gardens we compared Lepidoptera species richness and abundance on native plants, non‐native congeners of those natives, and non‐native species with no close relatives in the study area. Non‐native plants supported significantly fewer caterpillars of significantly fewer specialist and generalist species even when the non‐natives were close relatives of native host plants. However, the effect size was smaller in the latter category indicating phylogenetic similarity to local natives may positively impact herbivory. Cluster analysis revealed that a non‐native plant congener often supports a lepidopteran community that is a subset of the similar, but more diverse community found on its native congener. The proportion of the Lepidoptera community consisting of specialist species was about five times larger across native species within sites compared to non‐native plant species. In addition, species accumulation trajectories suggested that in a fully sampled community the differences between the Lepidoptera supported by native and non‐native plants may be even greater than presented here.

Effects of bacterial secondary symbionts on host plant use in pea aphids

Aphids possess several facultative bacterial symbionts that have important effects on their hosts' biology. These have been most closely studied in the pea aphid (Acyrthosiphon pisum), a species that feeds on multiple host plants. Whether secondary symbionts influence host plant utilization is unclear. We report the fitness consequences of introducing different strains of the symbiont Hamiltonella defensa into three aphid clones collected on Lathyrus pratensis that naturally lack symbionts, and of removing symbionts from 20 natural aphid-bacterial associations. Infection decreased fitness on Lathyrus but not on Vicia faba, a plant on which most pea aphids readily feed. This may explain the unusually low prevalence of symbionts in aphids collected on Lathyrus. There was no effect of presence of symbiont on performance of the aphids on the host plants of the clones from which the H. defensa strains were isolated. Removing the symbiont from natural aphid-bacterial associations led to an average approximate 20 per cent reduction in fecundity, both on the natural host plant and on V. faba, suggesting general rather than plant-species-specific effects of the symbiont. Throughout, we find significant genetic variation among aphid clones. The results provide no evidence that secondary symbionts have a major direct role in facilitating aphid utilization of particular host plant species.

Effects of natural enemies and host plants in wild and orchard habitats on obliquebanded leafroller (Lepidoptera: Tortricidae) larval survival

Observations suggest that the summer generation of a native, tortricid leafroller, Choristoneura rosaceana (Harris) is scarce in undisturbed, wild habitats but often abundant in managed apple orchards. We conducted experiments to determine whether these differences are attributable to differential impact of natural enemies in these two habitats and/or differences in host plant suitability. Laboratory-raised C. rosaceana larvae were implanted in dogwood ( Cornus spp.) dominated wild habitats and in apple orchards to investigate habitat effects on natural enemy inflicted larval mortality. The proportion of released larvae that established feeding sites on apple trees and dogwood plants were similar. Parasitism and predation were similar in both habitats, suggesting that resources required by natural enemies were not different in these two habitats. Relative rates of parasitism by some parasitoid species differed on dogwood and apple plants when both plant species occurred in wild habitats. There was evidence that some parasitoid species were differentially abundant between the two habitats. To test whether development time or pupal weight was affected by the food source, F1 generations of larvae collected in both habitats were fed with apple and dogwood in the laboratory. Initiation of pupation occurred 3 days later if larvae consumed dogwood compared to apple; however, the food source did not affect pupal weight. These results suggest that there are opportunities to enhance conservation biological control of C. rosaceana in apple orchards.

2008-2009년 충북지역 벼 줄무늬잎마름병 발생 요인 분석

충북지역의 벼 줄무늬잎마름병 발생 요인을 분석하기 위하여 2008년과 2009년 충북도내 청원, 진천, 보은 등 3개 지역에서 월동 애멸구 보독충율 및 애멸구 밀도, 자연 기주 식물의 바이러스 감염율, 농가 포장에서의 벼 줄무늬잎마름병 발생율을 조사하였다. 월동 애멸구의 보독충율은 2008년에 0%, 2009년에는 1.1%로 나타났다. 2009년 6월 상순 채집된 시료의 보독충율은 진천 1.4%, 보은 4.2%로 월동 애멸구의 보독충율보다 높게 나타났으며 이는 2009년 중국에서 비래한 애멸구 성충 집단과 관련이 있는 것으로 추정된다. 월동 애멸구 밀도는 2008년에는 청원 3.8, 진천 7.5, 보은 20.8마리/<TEX>$m^2$</TEX>, 2009년에는 청원 8.4, 진천 13.1, 보은 14.6마리/<TEX>$m^2$</TEX>로 나타났다. 2009년 2차조사(5월 상순)와 3차 조사(6월 상순)에서도 매우 낮은 밀도를 보였으나 3차 조사 시기에 일부 지점에서는 성충 태로 높은 밀도를 나타냈으며 이들은 국내에서 월동한 애멸구가 아닌 2009년 중국에서 비래한 애멸구 집단과 관련이 있는 것으로 추정된다. 자연 기주 식물에서 RSV가 감염된 시료는 없었다. 따라서 이러한 결과로부터 월동애멸구의 낮은 보독충율과 밀도, 자연 기주 식물의 낮은 감염율 및 적절한 재배관리 등 복합적 요인으로 인하여 지금까지 충북지역에서 RSV 발생이 낮았던 것으로 사료된다. The occurrence factors of Rice stripe virus (RSV) in Chungcheongbukdo were analyzed by investigating the viruliferous insect rate (VIR) of overwintered small brown plant hopper (SBPH), the population density of SBPH, the infection rate of natural host plants, and the occurrence rate of RSV on rice paddy fields at the 3 areas of Cheongwon, Jincheon, and Boeun in 2008 and 2009. The average VIR of overwintered SBPH was 0.0% in 2008 and 1.1% in 2009. From SBPH collected on early June in 2009, VIR was higher as 1.4% at Jincheon and 4.2% at Boeun than those of overwintered SBPH, and this higher VIR might relate stronlgy with the adult population of SBPH immigrated from China. The populations of SBPH at Cheongwon, Jincheon and Boeun in 2008 were 3.8, 7.5 and 20.8 Head/<TEX>$m^2$</TEX>, respectively. However, those of Cheongwon and Jincheon increased up to about two folds as 8.4 and 13.1 in 2009. No RSV was detected on the natural host plants including barley. The factors involved in RSV occurrence were affected negatively by the low VIR of overwintered SBPH, the low population of overwintered SBPH, the low infection rate of RSV on the natural host plants, and the clean cultivation environment in Chungcheongbukdo.

Development and Validation of Node-Based Sample Units for Estimating Soybean Aphid (Hemiptera: Aphididae) Densities in Field Cage Experiments

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is currently the most important insect threat to soybean, Clycine max (L.) Merr., production in the North Central United States. Field cage studies are a key tool in investigating the potential of natural enemies and host plant resistance to control this pest. However, a major constraint in the use of cage studies is the limited number of treatments and replicates that can be used as aphid densities frequently become so large as to limit the number of experimental units that can be quantified. One way to overcome this limitation is to develop methods that estimate whole-plant aphid densities based on a reduced sampling plan. Here, we extend an existing method, node-sampling, used for estimating aphid populations in open field conditions and apply it to caged populations. We show that parameters calculated under open field conditions are inappropriate to estimate caged populations. In contrast, using four independent data sets of caged populations and a cross-validation technique, we demonstrate that a three-node sampling unit and a weighted formula provide accurate and robust estimates of whole-plant aphid density. This method reduced the number of aphids counted per plant by and average of 60%, with greater reductions at higher aphid densities. We further demonstrate that nearly identical statistical results were obtained when whole-plant or node-sampling estimates were used in the analysis of two case studies. The reduced sample unit method developed here saves time without sacrificing efficiency so that more plants, replications, or studies can be conducted that will lead to improved soybean aphid management.

Reproductive capacities and development of a seed Bruchid beetle, Acanthoscelides macrophthalmus, a potential host for the mass rearing of the parasitoid, Dinarmus basalis.

The reproductive capacities and development of the seed beetle Acanthoscelides macrophthalmus (Schaeffer) (Coleoptera: Bruchidae), found in Togo, were determined under natural conditions in a Guinean zone for its use as a substitute host for the mass rearing of the parasitoid Dinarmus basalts Rond (Hymenoptera: Pteromalidae), a biological agent for the control of beetles that are pests of cowpea, Vigna unguiculata (L.) Walpers (Fabales: Fabaceae). Population dynamics at the field level; and survival, fecundity and offspring production by A. macrophthalmus under laboratory conditions were measured when fed on its natural plant-host Leucaena leucocephala (Lamark) deWit (Fabales: Mimosaceae). The data resulting from the laboratory study were used to calculate the demographic parameters of A. macrophthalmus by establishing its fertility and life tables. Contrary to cultivated leguminous food plants, L. leucocephala is a perennial sub-spontaneous leguminous plant whose pods are available year round. Although A. macrophthalmus was present in nature throughout the year, its infestation rate of the pods fluctuated according to the phenology of the plant. The maximum infestation of L. leucocephala pods was observed between August and December. Four larval stages and one pupal stage of A. macrophthalmus were identified in the laboratory. The total mean development time varied on average 33.75 ± 2.87 days on the mature pods and 33.39 ± 2.02 days on seeds. The adult female lived from one to two weeks. During its life time, the female laid an average of 62.3 ± 19 and 43.1 ± 13 eggs on the mature pods and seeds respectively and produced an average of 36.7 ± 11.3 offspring on the mature pods and 21.8 ± 8.4 offspring on seeds. On seeds, the net reproduction rate was 5.88 females per female and the intrinsic rate of population increase 0.051 per day. The generation time was 34.59 days and the doubling time 13.59 days. The demographic parameters of A. macrophthalmus in this study are close to those of Callobruchus maculatus F. (Bruchidae), the natural host of D. basalts in a previous study. A. macrophthalmus could therefore be used as substitute host for the mass rearing of D. basalts and subsequently its release in farmers' storage containers. The data presented in this study provide some baseline information regarding the reproductive capacities of A. macrophthalmus that may be useful for its promotion as a substitute host for mass rearing of D. basalts.

Expression of sweet pepper Hrap gene in banana enhances resistance to Xanthomonas campestris pv. musacearum

Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. musacearum, is the most devastating disease of banana in the Great Lakes region of Africa. The pathogen's rapid spread has threatened the livelihood of millions of Africans who rely on banana fruit for food security and income. The disease is very destructive, infecting all banana varieties, including both East African Highland bananas and exotic types of banana. In the absence of natural host plant resistance among banana cultivars, the constitutive expression of the hypersensitivity response-assisting protein (Hrap) gene from sweet pepper (Capsicum annuum) was evaluated for its ability to confer resistance to BXW. Transgenic lines expressing the Hrap gene under the regulation of the constitutive CaMV35S promoter were generated using embryogenic cell suspensions of two banana cultivars: 'Sukali Ndiizi' and 'Mpologoma'. These lines were characterized by molecular analysis, and were challenged with Xanthomonas campestris pv. musacearum to analyse the efficacy of the Hrap gene against BXW. The majority of transgenic lines (six of eight) expressing Hrap did not show any symptoms of infection after artificial inoculation of potted plants in the screenhouse, whereas control nontransgenic plants showed severe symptoms resulting in complete wilting. This study demonstrates that the constitutive expression of the sweet pepper Hrap gene in banana results in enhanced resistance to BXW. We describe the development of transgenic banana varieties resistant to BXW, which will boost the arsenal available to fight this epidemic disease and save livelihoods in the Great Lakes region of East and Central Africa.

The first DNA 1-like α satellites in association with New World begomoviruses in natural infections

From Brazilian weeds with typical symptoms of a geminivirus infection, the DNAs of two new virus species, two new strains with two variants of already known bipartite begomoviruses were sequenced. Moreover, the first two DNA 1-like satellites (α satellites) occurring naturally in the New World were identified. They are related to nanoviral DNA components and show a typical genome organization with one open reading frame coding potentially for a replication-associated protein (Rep), a conserved hairpin structure, and an A-rich region. After coinoculation with their helper begomoviruses ( Euphorbia mosaic virus, EuMV or Cleome leaf crumple virus, ClLCrV) the satellite DNAs were transmitted to experimental and natural host plants. Three of the begomovirus isolates (EuMV and ClLCrV) infected Arabidopsis thaliana plants, induced mild symptoms, and one of these (ClLCrV) transreplicated the satellite efficiently. As a result, several novel tools for molecular analyses of this important model plant are provided.

Replication of Grapevine leafroll-associated virus-7 (GLRaV-7) by Cuscuta Species and Its Transmission to Herbaceous Plants.

Grapevine leafroll-associated virus-7 (GLRaV-7) was transmitted from an Albanian grapevine accession to Tetragonia expansa by the parasitic dodder Cuscuta reflexa and to Nicotiana occidentalis by Cuscuta europea. Cuscuta campestris was infected by GLRaV-7 but could not transfer the virus to an experimental host. Transmission of the virus was verified by reverse transcription-polymerase chain reaction (RT-PCR) from total nucleic acid (TNA) and double-stranded RNA (dsRNA) extracts from all five plant species. DsRNA extractions separated on agarose gels showed strong visible bands corresponding to high-molecular-weight virus genome and to subgenomic RNA. GLRaV-7 was maintained in C. reflexa, C. campestris, T. expansa, and N. occidentalis for more than 4 years. Infected T. expansa and the Cuscuta species remained symptomless while N. occidentalis showed severe symptoms leading to stunting and decline of the plants. Quantitative PCR showed great differences in the titer of GLRaV-7 between the tissues of its natural and experimental host plants. This is the first report on a virus of the Closteroviridae that was successfully transmitted to an herbaceous plant by dodder. Virus replication could be demonstrated in Cuscuta. Both the new experimental hosts of GLRaV-7 and Cuscuta allowed extraction of dsRNA for further characterization of the viral genome, which previously required grapevine scraping of phloem. This is time-consuming and does not always lead to satisfactory results. These alternative hosts of GLRaV-7 facilitate nucleic acid extractions and could be used as model plants for etiological studies.

Effects of Hemlock Woolly Adelgid and Elongate Hemlock Scale on Eastern Hemlock Growth and Foliar Chemistry

In the eastern United States, two invasive specialist insects share a native host plant, Eastern hemlock, Tsuga canadensis. In recent years, much research has focused on the impacts of the hemlock woolly adelgid (Adelges tsugae) because of the detrimental effects it has on hemlock growth and survival. In contrast, the invasive elongate hemlock scale (Fiorinia externa) is thought to have only minor impacts on hemlock. We infested hemlock saplings with each insect and compared them with control (i.e., neither insect herbivore) saplings to assess how early infestations impact Eastern hemlock health (measured using new branch growth, foliar %N, and C:N ratio). Our study showed that, at equal densities, the two insects differed in their effect on Eastern hemlock. F. externa did not impact plant growth or foliar chemistry over the course of the 2-yr experiment. A. tsugae significantly reduced plant growth and caused a reduction of %N in the first year of the experiment. By the end of the experiment, A. tsugae trees had the same %N in their foliage as control and F. externa trees but drastically reduced growth patterns. The most likely explanation for this result is the greater growth in control and F. externa saplings during the second year resulted in the dilution of available foliar N over a larger amount of newly produced plant tissue. For early infestations of both insects, our study suggests that management plans should focus on the more detrimental A. tsugae.

Evolutionary divergence of field and laboratory populations of Manduca sexta in response to host‐plant quality

1. The tobacco hornworm, Manduca sexta, has been an important model system in insect biology for more than 50 years. In nature, M. sexta successfully utilises a range of host plants that vary in quality. The consequences of laboratory domestication and rearing on artificial diet for fitness of phytophagous insects on natural host plants have not been explored.2. We examine the evolutionary divergence of two domesticated laboratory populations and a field population (separated for more than 40 years, or &gt; 250 laboratory generations) of M. sexta with respect to performance and fitness on two natural host plants: a typical host plant, tobacco (Nicotiana tabacum) and a novel host plant, devil's claw (Proboscidea louisianica).3. For both field and laboratory populations, rearing on devil's claw resulted in animals with lower survival, smaller final size, longer development time, and reduced size‐corrected fecundity than animals reared on tobacco. Reductions in some fitness components (survival and fecundity) were greater for the laboratory population animals than the field population animals.4. When reared on tobacco, the laboratory population animals had similar or larger pupal masses and slightly shorter development times than when reared on artificial diet, suggesting that laboratory domestication on artificial diet has not greatly affected the ability of M. sexta to perform well on a typical natural host plant.5. Although field and laboratory populations exhibited qualitatively similar responses to host‐plant quality, i.e. reduced performance on devil‘s claw, the magnitude of this reduction differed across populations, with the domesticated laboratory populations having greater reductions in performance than the field population. The use of domesticated populations as models for responses of field populations may therefore be more appropriate for considering environmental conditions that are relatively benign or near‐optimal, than when exploring responses to extreme or stressful conditions.

Trichoferus campestris(Faldermann) (Coleoptera: Cerambycidae), An Asian Wood-Boring Beetle Recorded in North America

ABSTRACT Two adult specimens of Trichoferus campestris (Faldermann, 1835), a newly detected alien wood-boring beetle native to Asia (Coleoptera: Cerambycidae), were collected in Repentigny, Quebec, Canada in 2002 and 2006. Adults, pupae, and mature larvae of this species are described, illustrated and diagnosed to facilitate its recognition among other North American Cerambycidae. The mtDNA sequence of the COI “barcoding” region of a Canadian specimen was obtained and analyzed. We discuss taxonomic affinities of T. campestris, its native distribution, host plants, and significance as a quarantine pest in North America. The importance of solid wood-packaging material as a potential pathway for invasive wood-boring species is highlighted. Seven other non-native Cerambycidae species first recorded in North America since 1980 [Tetropium fuscum (Fabricius, 1787), Anoplophora glabripennis (Motschulsky, 1853), Tetrops praeusta (Linnaeus, 1758), Callidiellum rufipenne (Motschulsky, 1860), Phoracantha semipunctata...

First Report of Cucumber mosaic virus Infecting Pinewood Coneflower (Rudbeckia bicolor) in Korea

Department of Plant Medicine, Chungbuk National University, Cheongju 361-763, Korea(Received on December 21, 2009; Accepted on February 15, 2010)A virus isolate causing symptoms of yellow mosaic, fernleaves, malformation and plant necrosis on Rudbeckiabicolor was prevalent around Pyeongchang area inKorea. The causal virus was identified as Cucumbermosaic virus (CMV) using characteristics from bio-logical, serological and molecular analyses and namedas CMV-Rb. CMV-Rb caused mosaic on Nicotianabenthamiana, N. tabacum, Capsicum annuum, and Lyco-persicon esculentum. However, typical local lesions didnot develop on inoculated Pisum sativum, Cucurbitamoschata, Datura stramonium and Tetragonia expansaplants. Full-length genome sequences of CMV-RbRNAs 1, 2 and 3 were obtained using 12 primer pairs byRT-PCR analysis. The genome of CMV-Rb RNA seg-ments 1, 2, and 3 consists of 3363nt, 3049nt, and 2214ntin length, respectively. In order to ascertain their taxo-nomic identity, nucleotide and the deduced amino acidsequence analyses RNAs 1, 2 and 3 of CMV-Rb isolateswere conducted with previously reported sequences ofCMV strains and/or isolates. CMV-Rb RNAs showedabout 90 to 99% sequence identity to those of subgroupI strains suggesting that CMV-Rb is more closely relat-ed to CMV isolates belong to subgroup I. To our know-ledge, this is the first report of CMV on Rudbeckiabicolor in Korea.Keywords : CMV-Rb, phylogenetic analyses, Rudbeckiabicolor, subgroup ICucumber mosaic virus (CMV), the type member of thegenus Cucumovirus, infects more than 1,000 species ofplants and induces the typical mosaic symptoms in manyhost plants. Some of the intermediate symptoms, however,include blight, fernleaf, ringspot, and stunt. In Korea, atleast 109 natural host plant species has been reported, i.e.,20 in upland crops, 20 in vegetable crops, 28 in floral crops,acacia in wood, 40 in wild plants (List of plant disease inKorea, 2004, The Korean Society of Plant Pathology).Recently, CMV infections were also reported on Hydrangeamacrophylla (Lee et al., 2001), water chickweed (Choi etal., 2004), Isodon inflexus Kudo, Jeffersonia dubia Benth,Phryma leptostachya var. asiatica Hara (Lee et al., 2008).However, no natural outbreaks by CMV have been reportedon Rudbeckia bicolor, but Bidens mottle virus (BiMoV)was only identified (Brunt et al., 1996; Choi, 2001; Jin,2003; Lee, 1981; Lee et al., 2003; Logan et al., 1984).The genome of CMV consists of three genomic RNAs(RNA 1, 2 and 3; Roossinck, 2001). In infected host plants,it also produces two subgenomic RNAs (4 and 4A; Palukaitiset al., 1992). Based upon biological, serological, and, mole-cular biological characteristics of CMV isolates, they wereclassified into two subgroups, i.e., subgroup I and II (Owenand Palukaitis, 1988). The nucleotide sequence identitybetween subgroup I and II isolates range from 69 to 77%,while showing above 90% nucleotide sequence identitywithin each subgroup isolates. More detailed nucleotidesequence analyses, especially with the coat protein (CP)and 5' nontranslated region (NTR) of RNA 3 further sug-gested subdivision of subgroup I into subgroups IA and IB(Roossinck et al., 1999). This subgrouping was more clear-ly supported from the analysis of nucleotide sequences of1a and 3a open reading frames (ORFs) than those of the 2aand CP ORFs (Roossinck, 2002). In this paper, we reportthe biological and serological characteristics as well ascomplete nucleotide sequence analyses of CMV-Rb isolate.We believe this is the first report of natural CMV infectionon Rudbeckia bicolor in Korea.Pinewood coneflower (R. bicolor), family Asteraceae, iswidely grown as an ornamental crop and a wildflower. In2005, we could easily observe yellow mosaic, sometimes

Antibiosis of Eucalyptus plants on Podisus nigrispinus

The predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) has been used as a natural enemy to control herbivorous insects in eucalyptus plantations. However, because of the short co-evolutionary history of the predator with this imported plant species, the defensive compounds of eucalyptus may have a negative effect on the predator. Therefore, the survival and development of P. nigrispinus were studied on eucalyptus (Eucalyptus urophylla; exotic host plant) and guava (Psidium guajava; native host plant). P. nigrispinus performance was indeed superior on guava plants than on eucalyptus. The number of fertile eggs and nymphal survival were 52.6% and 12.0% on guava compared with 20.0% and 1.3% on eucalyptus, respectively. Longevity of P. nigrispinus was 115 days on guava and 98 days on eucalyptus. This shows that the predator is not yet fully adapted to the exotic host plant. One possible reason is that the plant toxic compounds in eucalyptus act on this predator by antibiosis.

Environmental Dependence of Thermal Reaction Norms: Host Plant Quality Can Reverse the Temperature‐Size Rule

The temperature-size rule, a form of phenotypic plasticity in which decreased temperature increases final size, is one of the most widespread patterns in biology, particularly for ectotherms. Identifying the environmental conditions in which this pattern is reversed is key to understanding the generality of the rule. We use wild and domesticated populations of the tobacco hornworm Manduca sexta and the natural host plants of this species to explore the consequences of resource quality for the temperature-size rule. Manduca sexta reared on a high-quality host, tobacco (Nicotiana tabacum), followed the temperature-size rule, with larger final sizes at lower temperatures. In contrast, M. sexta reared on a low-quality host, devil's claw (Proboscidea louisianica), showed the reverse response. Wild and domesticated M. sexta exhibited qualitatively similar responses. Survival, growth and development rates, fecundity, and final size decreased with decreasing temperature in M. sexta reared on devil's claw. We propose that the reversal of the temperature-size rule results from the stressful combination of low temperatures and low dietary quality. Such reversals may impact seasonal and geographic patterns of host use in Manduca and other systems. Our results suggest that the temperature-size rule occurs for a restricted range of nonstressful environmental conditions, limiting the robustness of this widespread pattern of phenotypic plasticity.