Leptocybe Research Articles

Population genetic analyses of complex global insect invasions in managed landscapes: a Leptocybe invasa (Hymenoptera) case study

Members of the Tree Protection Co-operative Programme (TPCP), the THRIP Initiative of the Department of Trade and Industry and the National Research Foundation (NRF) (NRF Grant Number 88227).

Development of Galls in Eucalyptus Due to Infestation of Leptocybe invasa and Its Effects on Growth of Seedlings.

Leptocybe invasa Fisher & LaSalle (Hymenoptera : Eulophidae), commonly known as blue gum chalcid wasp, is a major gall making insect species of eucalyptus, causing serious damage to seedlings in nursery stage. An insectary/nursery of eucalyptus was developed at this Institute to study the stages of gall development, number of galls formed with the age of seedling and effects of galls on the growth of seedling. Results revealed that there are five distinct stages of gall development, first stage initiates by the insertion of eggs on the epidermis of soft young leaves, petioles and stems and final stage ends with the emergence of adult wasps from galls through exit holes. It was observed that the development of galls start after one month age of seedlings, and there was significant (P<0.05-P<0.01) variation in growth (height and collar diameter), number of galls in leaves, petioles and stems, and total number of galls/seedling in respect of age. The data clearly exhibited that one month old seedlings were free from the attack of L. invasa as because there was complete absence of galls. Further, it was recorded that seedlings growth (height and collar diameter) was affected by the development of galls, minimum growth was recorded in case of maximum galls developed whereas less galls were noticed for maximum growth of seedlings. There was an inverse relationship exists between seedling growth and development of galls. The practical application of findings was discussed in the light of the present observations.

The Distribution and Management of Two Invasive Pests of Eucalyptus: The Red Gum Lerp Psyllid, Glycaspis brimblecombei (Hemiptera: Psylloidae), and the Blue Gum Chalcid Wasp, Leptocybe invasa (Hymenoptera: Eulophidae), in Zimbabwe

Eucalyptus species are indigenous to Australia but arenowgrown worldwide due to their fast growth rate and various uses as timber and fuel wood. Insect pests of Eucalyptus have since followed their host and, in most cases, leaving behind the natural enemies which usually regulate them below economic injury. This is the case with Glycaspis brimblecombei and Leptocybe invasa which are now resident in most parts of the world including Zimbabwe. Damage as a result of the two pests currently poses a threat to reforestation efforts to provide alternative sources of firewood for curing tobacco. The objective of this study was to determine the distribution of the two pests as well as assess the possibility of managing L. invasa through biological control by releasing and recovering successive generations of the natural enemy Selitrichodes neseri in selected L. invasa-infested areas. Surveys were therefore carried out in Zimbabwe and GPS coordinates for pest presence recorded and used to determine the current distribution and future projections of the two pests using Maximum Entropy (maxent) ecological niche modelling. In preliminary studies to manage L. invasa, the natural wasp enemy S. neseri was released in Eucalyptus plantations and recovery studies done to establish their perpetuation in the field. Based on temperature and precipitation averages for Zimbabwe, the model predicted widespread distribution of the two pests especially in Mashonaland West, Bulawayo, Harare, Midlands province and parts of Manicaland province. This predicted range was projected to shrink due to climate change by the year 2055. In terms of relative contribution in predicting the distribution of the occurrence data, the three most important variables were mean annual temperature (39 %), mean temperature coolest month (18.3%)and annual moisture index (18 %). The performance of the model was high, with an AUC value of 0.884. Selitrichodes neseri wasps were recovered in infested Eucalyptus samples 4–6 generations after the initial release, indicating a high possibility of the natural enemy being able to establish in the future. Our findings are therefore important in understanding the current and projected distribution of both L. invasa and G. brimblecombei in Zimbabwe and formulating management measures for the two pests.

The first identification of genomic loci in plants associated with resistance to galling insects: a case study in Eucalyptus L'H\xe9r. (Myrtaceae)

Genomic loci related with resistance to gall-inducing insects have not been identified in any plants. Here, association mapping was used to identify molecular markers for resistance to the gall wasp Leptocybe invasa in two Eucalyptus species. A total of 86 simple sequence repeats (SSR) markers were screened out from 839 SSRs and used for association mapping in E. grandis. By applying the mixed linear model, seven markers were identified to be associated significantly (P ≤ 0.05) with the gall wasp resistance in E. grandis, including two validated with a correction of permutation test (P ≤ 0.008). The proportion of the variance in resistance explained by a significant marker ranged from 3.3% to 37.8%. Four out of the seven significant associations in E. grandis were verified and also validated (P ≤ 0.073 in a permutation test) in E. tereticornis, with the variation explained ranging from 24.3% to 48.5%. Favourable alleles with positive effect were also mined from the significant markers in both species. These results provide insight into the genetic control of gall wasp resistance in plants and have great potential for marker-assisted selection for resistance to L. invasa in the important tree genus Eucalyptus.

Selitrichodes neseri (Hymenoptera: Eulophidae) Recovered from Leptocybe invasa (Hymenoptera: Eulophidae) Galls After Initial Release on Eucalyptus (Myrtaceae) in Brazil, and Data on Its Biology

Abstract Blue gum chalcid, Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae), causes galling damage to Eucalyptus species (Myrtaceae) in various regions of the world, but has been controlled effectively by its primary parasitoid, Selitrichodes neseri Kelly & La Salle (Hymenoptera: Eulophidae). The objectives of this study were to evaluate the recovery of S. neseri after its initial release on Eucalyptus plants in Brazil and to provide data on its biology. Selitrichodes neseri was imported from South Africa to Brazil for the biological control of L. invasa, in Mar 2015, and recovered from Aug 2015 to Dec 2016. Successful recovery of this parasitoid shows its potential to become established in the field. Seedlings of 2 hybrids obtained from crosses between rose gum Eucalyptus grandis W. Hill. ex Maiden and flooded gum Eucalyptus urophylla S. T. Blake and between Eucalyptus sp. and (river red gum Eucalyptus camaldulensis Dehnh. × E. grandis) showed potential as hosts for culture of S. neseri on L....

The gall wasp Leptocybe invasa (Hymenoptera: Eulophidae) stimulates different chemical and phytohormone responses in two Eucalyptus varieties that vary in susceptibility to galling.

Gall-inducing insects produce various types of galls on plants, but little is known about the gall-induction mechanism of these galling insects. The gall wasp Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) forms galls of different sizes on several Eucalyptus species. To clarify the physiological responses of Eucalyptus to L. invasa infestation, we measured the dynamics of nitrogen (N), carbon (C), total phenolics, total tannins and four types of phytohormones (zeatin [Z] + zeatin riboside [ZR], gibberellins [GA], indole-3-acetic acid [IAA] and abscisic acid [ABA]) in galled and ungalled leaf tissues of two Eucalyptus horticultural varieties (DH201-2 [Eucalyptus grandis × Eucalyptus camaldulensis] and EA [Eucalyptus exserta]) with different susceptibility to galling throughout the larval developmental stages. Nitrogen, total phenolics, tannins and four kinds of phytohormones strongly accumulated in tissues galled by L. invasa (especially during early larval feeding stages). While N, Z + ZR and GA levels were higher, tannins and ABA levels were lower in the galled tissues on the highly susceptible variety. Nitrogen, total phenolics, GA, Z + ZR and IAA levels in the galled tissues gradually decreased during gall development, but ABA and tannins conversely increased in the galled tissues of the less susceptible variety. Our results suggest that the effects of gall-inducing insects on plants depend not only on the susceptibility of the plant infested but also on the developmental stage of galled tissues. Gall formation process is thus synergistically influenced by both gall-inducing insect and plant genotypes.

Life inside a gall: closeness does not favour horizontal transmission of Rickettsia between a gall wasp and its parasitoid.

The incidence of horizontal transmission as a route for spreading symbiont infections is still being debated, but a common view is that horizontal transfers require intimate between-species relationships. Here we study a system that meets ideal requirements for horizontal transmission: the gall wasp Leptocybe invasa and its parasitoid Quadrastichus mendeli (Hymenoptera: Eulophidae). These wasps belong to the same subfamily, spend most of their lives inside the same minute gall and are both infected by Rickettsia, a maternally inherited endosymbiotic bacteria that infects several arthropods, sometimes manipulating their reproduction, like inducing thelytokous parthenogenesis in L. invasa. Despite intimate contact, close phylogenetic relationship and the parasitoid's host specificity, we show that host and parasitoid do not share the same Rickettsia. We provide indirect evidence that Rickettsia infecting Q. mendeli may be inducing thelytokous parthenogenesis, as the symbiont is densely present in the reproductive apparatus and is vertically transmitted. Phylogenetic analyses based on 16S and gltA placed this symbiont in the leech group. The confirmed and presumed parthenogenesis-inducing Rickettsia discovered so far only infect eulophid wasps, and belong to three different groups, suggesting multiple independent evolution of the parthenogenesis inducing phenotype. We also show some degree of cospeciation between Rickettsia and their eulophid hosts.

First record of Quadrastichus mendeli, a parasitoid of Leptocybe invasa, in South Africa

Leptocybe invasa, the blue gum chalcid, is a well-known pest of Eucalyptus globally. Since it was first observed in the Mediterranean and Middle East in 2000, it has spread to other countries where Eucalyptus have been planted. Efforts to control it have included the release of a number of larval and pupal parasitoids. This report serves as the first record of the presence of Quadrastichus mendeli in South Africa, a parasitoid originally released as a biological control agent of L. invasa in Israel. The interactions and potential impacts on the other insects in the L. invasa galls will need to be investigated.

Alternative eucalypts for commercial pulpwood production at moderately dry sites in the warm temperate zone of KwaZulu-Natal, South Africa

During 2001, a series of four site–taxa interaction trials was established in the warm temperate (mean annual temperature range 16–19 °C) forestry climatic zone of KwaZulu-Natal (KZN), South Africa. The main objective was to investigate the commercial forestry potential of a range of alternative Eucalyptus and Corymbia taxa for moderately dry (mean annual precipitation < 850 mm) sites within the zone. At rotation end, all trials received final standing tree measurements. At one of the sites (Rockvale), trees of eight promising alternative taxa were felled, stem measurements and wood samples taken, and wood and fibre productivities determined. On the basis of tree growth and wood and fibre production, C. citriodora subsp. variegata, C. henryi, E. badjensis, E. benthamii and E. dorrigoensis (listed alphabetically) demonstrated the greatest potential as commercial alternatives for moderately dry sites in the KZN warm temperate zone. The majority of these taxa showed strong site specificity. Eucalyptus benthamii was the only taxon showing high growth adaptability to the entire range of site conditions applied in the series. The non-susceptibility of C. citriodora subsp. variegata and C. henryi to the current topical insect pests Thaumastocoris peregrinus, Leptocybe invasa and Glycaspis brimblecombei elevates the appeal of these taxa as potential alternative planting choices for moderately dry sites within lower altitude (<1 100 m asl) areas of the climate zone. The matching of the most promising alternative taxa in the series to the range of sites encountered in moderately dry areas of the KZN warm temperate forestry zone is discussed in this paper.

Reproductive Biology of Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae).

Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is an invasive pest in Eucalyptus plantations around the world. The successful colonization of L. invasa is possibly related to its reproductive biology. The objective of this study was to examine the reproductive biology of L. invasa. In Guangxi Province, the sex ratio (proportion of female, 0.99) of L. invasa was female-dominant throughout the year based on natural and artificial infestation. This result was similar to the ratios observed for other geographic populations in China, including those in Fujian (0.99), Guangdong (0.98), Hainan (0.95), Jiangxi (0.96), and Sichuan (0.99). The offspring sex ratio favored females. A large number of females emerged from the galls produced by females, with few males found. Galls on the petioles and midribs of Eucalyptus plants could be caused by newly emerged females with mature eggs. The lengths of the ovariole, spermatheca, common oviduct, and reproductive glands did not differ among L. invasa females, but their lateral oviducts showed differences from 0 to 42h after emergence, indicating that this insect is proovigenic. These results could explain why L. invasa populations can rapidly increase in invaded areas.

Identification of the Eucalyptus grandis chitinase gene family and expression characterization under different biotic stress challenges.

Eucalyptus grandis (W. Hill ex Maiden) is an Australian Myrtaceae tree grown for timber in many parts of the world and for which the annotated genome sequence is available. Known to be susceptible to a number of pests and diseases, E. grandis is a useful study organism for investigating defense responses in woody plants. Chitinases are widespread in plants and cleave glycosidic bonds of chitin, the major structural component of fungal cell walls and arthropod exoskeletons. They are encoded by an important class of genes known to be up-regulated in plants in response to pathogens. The current study identified 67 chitinase gene models from two families known as glycosyl hydrolase 18 and 19 (36 GH18 and 31 GH19) within the E. grandis genome assembly (v1.1), indicating a recent gene expansion. Sequences were aligned and analyzed as conforming to currently recognized plant chitinase classes (I-V). Unlike other woody species investigated to date, E. grandis has a single gene encoding a putative vacuolar targeted Class I chitinase. In response to Leptocybe invasa(Fisher & La Salle) (the eucalypt gall wasp) and Chrysoporthe austroafricana (Gryzenhout & M.J. Wingf. 2004) (causal agent of fungal stem canker), this Class IA chitinase is strongly up-regulated in both resistant and susceptible plants. Resistant plants, however, indicate greater constitutive expression and increased up-regulation than susceptible plants following fungal challenge. Up-regulation within fungal resistant clones was further confirmed with protein data. Clusters of putative chitinase genes, particularly on chromosomes 3 and 8, are significantly up-regulated in response to fungal challenge, while a cluster on chromosome 1 is significantly down-regulated in response to gall wasp. The results of this study show that the E. grandis genome has an expanded group of chitinase genes, compared with other plants. Despite this expansion, only a single Class I chitinase is present and this gene is highly up-regulated within diverse biotic stress conditions. Our research provides insight into a major class of defense genes within E. grandis and indicates the importance of the Class I chitinase.

桉树杂交种对桉树枝瘿姬小蜂的抗性变异分析

PDF HTML阅读 XML下载 导出引用 引用提醒 桉树杂交种对桉树枝瘿姬小蜂的抗性变异分析 DOI: 10.5846/stxb201606191192 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31360458，31460115，31660087）；广西农科院科技发展基金（2014YP10，2015YT97）；中国博士后基金（2014M552286） Analysis of variable resistance in Eucalyptus hybrids to Leptocybe invasa Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植物种间杂交是一种普遍自然现象，杂交往往造成植物表型及生理变异，从而改变杂种抗虫性。与亲本种相比，杂种抗虫性可能增强或减弱，也有可能处于与亲本相似水平。初生、次生代谢物的质变与量变是引起杂种抗虫性变异的重要原因。近年来，桉树杂交育种已在世界范围内广泛应用并取得了显著成效，桉树杂交种间抗虫性表现参差不齐，因此，桉树是研究杂交种抗虫性变异机制的理想材料。以2个桉树杂交种巨细桉DH201-2、巨尾桉G9及桉树重要害虫桉树枝瘿姬小蜂为研究对象，比较了2个杂交种与其纯亲本种[（巨桉×细叶桉），（巨桉×尾叶桉）]间的抗虫性差异；同时，综合比较了品系间叶片性状（叶片厚度、含水率、比叶面积）、初生化合物（C、N、可溶性糖、可溶性蛋白）及次生化合物（总酚、单宁）差异，以研究桉树杂交种抗虫性变异的理化机制。结果表明：DH201-2感染桉树枝瘿姬小蜂的虫瘿数目显著高于其双亲本种，而G9上虫瘿数目显著低于其双亲本种。DH201-2与G9的叶片厚度与巨桉相近，而显著薄于另一亲本种。DH201-2叶片含水率显著高于细叶桉、与巨桉相近；G9叶片含水率则显著低于其双亲本种。相似的是，DH201-2和G9的比叶面积均显著高于其双亲本种。初生化合物方面，DH201-2叶片可溶性糖和可溶性蛋白含量均显著高于其亲本种，N含量则仅高于细叶桉；而G9叶片可溶性蛋白含量虽高于其双亲本种，可溶性糖含量则无显著差异，N含量显著低于其双亲本种。次生化合物方面，DH201-2叶片总酚和单宁含量显著低于其双亲本种，而G9则显著高于其双亲本种。因此，与其亲本种相比，DH201-2感虫性增加，而G9抗虫性增加；与桉树枝瘿姬小蜂发育相关的营养指标（如含水率、可溶性糖、N含量）及次生防御物质（如总酚、缩合单宁）在桉树杂交种组织内的含量差异影响了桉树杂交种对桉树枝瘿姬小蜂的抗性。在全球推行桉树杂交育种且桉树害虫数量逐年增加的大背景下，应加强对桉树杂交种抗虫性机制研究，为选育高抗品系及桉树产业可持续发展提供理论指导。 Abstract:Interspecific hybridization is a common phenomenon in plants, and it often causes substantial changes in phenotypic and physiological traits, resulting in various resistance abilities to herbivores and pathogens among hybrids. Compared to their parents, hybrids exhibit lower resistance, higher resistance, or intermediate resistance. Qualitative or quantitative changes in primary and secondary compounds in hybrids are important factors affecting their herbivore resistance. Hybrid breeding technology has been widely applied in the Eucalyptus industry, and achieved remarkable success worldwide in recent years. As Eucalyptus hybrids vary in their ability to resist herbivores, they provide an ideal system to investigate the mechanisms underlying herbivore resistance in hybrids. To elucidate the herbivore resistance variance mechanisms, two Eucalyptus hybrids, DH201-2 (E. grandis × E. tereticornis) and G9 (E. grandis × E. urophylla), and an important Eucalyptus pest, Leptocybe invasa, were chosen for study. The resistance of DH201-2, G9, and their pure parental species (E. grandis and E. urophylla, E. grandis and E. tereticornis, respectively) against L. invasa were compared. In parallel, comprehensive measurements were taken to assess differences in leaf traits (leaf thickness, water content, and specific leaf area), primary compounds (C, N, soluble sugar, and soluble protein), and secondary compounds (total phenolics and condensed tannins) among the two hybrids and their parental species. The results showed that gall number on DH201-2 was significantly more than on its two paternal species, while gall number on G9 was significantly less than on its two parental species. Leaf thickness of DH201-2 and G9 were similar to E. grandis, but their leaves were thinner than those of the other parental species. Leaf water content in DH201-2 was significantly higher than that in E. tereticornis but similar to that in E. grandis, whereas G9 contained significantly lower water content than its two parental species. Similarly, both the specific leaf area of DH201-2 and G9 were significantly larger than their parental species. Considering the primary compounds, DH201-2 contained significantly more soluble sugar and soluble protein than its parental species, and more N than E. tereticornis. Although the content of soluble protein was significantly higher in G9, soluble sugar and N content were similar and lower than those in its two parental species, respectively. Both total phenolics and condensed tannins in DH201-2 were significantly lower than those in its parental species; however, they were significantly higher in G9 than in its two parental species. Therefore, we conclude that compared with the respective parental species, DH201-2 is more susceptible and G9 is more resistant to L. invasa. Different expressions of nutritional substances that are closely related to the development of L. invasa (i.e., water content, soluble sugar, and N content), and secondary defensive substances such as total phenolics and condensed tannins in Eucalyptus hybrids, together generate variable resistance abilities to L. invasa. In the context of the wide development of Eucalyptus hybrid breeding and the gradual increase in Eucalyptus pests over the years, more research focusing on the resistance variance mechanisms underlying Eucalyptus hybrids is required. These studies could provide valuable scientific guidance not only for screening herbivore-resistant hybrids through crossbreeding but also for the sustainable development of future Eucalyptus plantations. 参考文献 相似文献 引证文献

English

A comparative study of the volatile terpene fraction isolated from the leaves of Eucalyptus camaldulensis attacked by the gall wasp (Leptocybe invasa) and from the healthy leaves of the plant was carried out using gas chromatography-mass spectrometry. A total of 59 components representing 89.13 and 88.6%, respectively, of their total volatile fraction contents were analyzed. Of these volatiles, 26 compounds with concentrations greater than (0.1± 0.02%) have been used for statistical comparison. A number of 21of these compounds were identified, in different concentrations, in the leaves volatile fraction of both healthy plants and plants attacked by the wasps. The other 5 volatiles: p-mentha-2-4(8) diene, δ-elemene, β-elemene, E-caryophyllene and bicyclogermacrene, were exclusively found in the volatile fraction of the attacked leaves. The newly produced compounds in the attacked leaves or the change in concentration of those commonly found in that fraction, could be part of the plant defense mechanisms, or/and an element of the plant allelopathic and communication mechanisms. Identifying the components of the gall wasp-damaged leaves can help in their recycling for different physiological, pharmacological and medicinal uses. Key words: Eucalyptus, gall wasp, plant defense mechanisms, plant recycling, terpene fraction.

Effect of the Gall Wasp Leptocybe invasa on Hydraulic Architecture in Eucalyptus camaldulensis Plants

The gall wasp, Leptocybe invasa (Hymenoptera; Eulophidae), is a devastating pest of eucalypt plantations in the Middle East, the Mediterranean basin, Africa, India, South-East Asia, and China. Heavy galling causes the leaves to warp and in extreme cases it may stunt the growth of the trees of Eucalyptus camaldulensis. However, the physiological mechanisms underlying how L. invasa inhibits the growth of plants of E. camaldulensis are unclear. Because the growth rate of plants is mainly dependent on photosynthesis that is largely correlated with hydraulic architecture, we speculate that galling of L. invasa depresses hydraulic conductance of stem and leaf. In the present study, we examined the effects of L. invasa galling on hydraulic architecture and photosynthetic parameters in E. camaldulensis plants. We found that galling of L. invasa significantly decreased stem hydraulic conductance (Kstem), midday leaf water potential (Ψmd), minor vein density, and stomatal density (SD). Furthermore, the stomatal conductance (gs), chlorophyll content, CO2 assimilation rate (An) and photosynthetic electron flow were reduced in infected plants. Therefore, the galling of L. invasa not only declined the water supply from stem to leaves, but also restricted water transport within leaf. As a result, galled plants of E. camaldulensis reduced leaf number, leaf area, SD and gs to balance water supply and transpirational demand. Furthermore, galled plants had lower leaf nitrogen content, leading to decreases in chlorophyll content, CO2 assimilation rate and photosynthetic electron flow. These results indicate that the change in hydraulic architecture is responsible for the inhibition of growth rate in galled plants.

Gall Insect Menace in Eucalyptus

Altogether about 920 species of insects recorded from Eucalyptus worldwide, about six species are gall insects. Of these, Leptocybe invasa, is a major nursery pest of Eucalyptus, exclusively responsible for gall formation in seedlings and saplings, including coppice shoots. The insect has threatened Eucalyptus propagation in nursery stage. The present paper has reviewed succinctly the insect pests of Eucalyptus with special emphasis on gall insect, Leptocybe invasa Fisher &amp; LaSalle (Hymenoptera : Eulophidae), its seasonal occurrence, nature of damage, host plants and description of gall insect, developmental stages of gall, natural enemies and management. The paper has highlighted the need for long term strategies to combat against this severe pest to prevent its spread.

The Eucalyptus grandis NBS-LRR Gene Family: Physical Clustering and Expression Hotspots.

Eucalyptus grandis is a commercially important hardwood species and is known to be susceptible to a number of pests and pathogens. Determining mechanisms of defense is therefore a research priority. The published genome for E. grandis has aided the identification of one important class of resistance (R) genes that incorporate nucleotide binding sites and leucine-rich repeat domains (NBS-LRR). Using an iterative search process we identified NBS-LRR gene models within the E. grandis genome. We characterized the gene models and identified their genomic arrangement. The gene expression patterns were examined in E. grandis clones, challenged with a fungal pathogen (Chrysoporthe austroafricana) and insect pest (Leptocybe invasa). One thousand two hundred and fifteen putative NBS-LRR coding sequences were located which aligned into two large classes, Toll or interleukin-1 receptor (TIR) and coiled-coil (CC) based on NB-ARC domains. NBS-LRR gene-rich regions were identified with 76% organized in clusters of three or more genes. A further 272 putative incomplete resistance genes were also identified. We determined that E. grandis has a higher ratio of TIR to CC classed genes compared to other woody plant species as well as a smaller percentage of single NBS-LRR genes. Transcriptome profiles indicated expression hotspots, within physical clusters, including expression of many incomplete genes. The clustering of putative NBS-LRR genes correlates with differential expression responses in resistant and susceptible plants indicating functional relevance for the physical arrangement of this gene family. This analysis of the repertoire and expression of E. grandis putative NBS-LRR genes provides an important resource for the identification of novel and functional R-genes; a key objective for strategies to enhance resilience.

Parasitoids of the eucalyptus gall wasp Leptocybe invasa (Hymenoptera: Eulophidae) in China.

Leptocybe invasa Fisher & La Salle (Hymenoptera, Eulophidae) is an invasive pest in Eucalyptus plantations throughout the world. Potential biological control agents for L. invasa were investigated in the Fujian, Guangdong, Hainan, Guangxi, Jiangxi, and Sichuan provinces of China, where Eucalyptus spp. have been severely damaged by the eucalyptus gall wasp. Three hymenopteran parasitoids of L. invasa were identified: Quadrastichus mendeli Kim & La Salle (Eulophidae), Aprostocetus causalis La Salle & Wu (Eulophidae), and Megastigmus viggianii Narendran & Sureshan (Torymidae); M. viggianii is newly recorded in China. The percentages of parasitization by Q. mendeli, A. causalis, and M. viggianii were 2.96%–19.53%, 2.30%–26.38%, and 24.93%, respectively. The longevity and body length of females were significantly greater than for males in A. causalis and M. viggianii. No males of Q. mendeli were found in China. These parasitoids could be used as biological agents for L. invasa in China.

Biological control of Eucalyptus gall wasp, Leptocybe invasa Fisher &amp; La Salle (Hymenoptera: Eulophidae) by its native parasitiods

Utilization of native parasitoids viz. Megastigmus dharwadicus Narendran and Vastrad (Hymenoptera: Torymidae) and Aprostocetus galaWalker (Hymenoptera: Eulophidae) for biological control of eucalyptus gall wasp, Leptocybe invasa Fisher and LaSalle (Hymenoptera: Eulophidae) is reported. Two native parasitoids multiplied in the greenhouse were released in a severely affected eucalyptus plantation spread over an area of 1000 ha. A total of 14,000 heavily parasitized galled seedlings, 1400 M. dharwadicus and 300 A. gala were distributed over a period of six months. The per cent parasitization by these native parasitoids was ascertained before distribution of galled seedlings. Though there was a gradual increase in per cent parasitization, the reduction in gall incidence was not evident up to three months. However, drastic reduction in gall incidence and pest emergence accompanied by very high per cent parasitization was evident within eight months. Post release evaluation conducted during June 2011 and May 2012 indicated the successful control of the pest.

Anatomía y morfogénesis de las agallas producidas por Leptocybe invasa en plantas de Eucalyptus

: Leptocybe invasa o “avispa de la agalla del eucalipto”, es un microhimenóptero gallícola que ovipone en hojas jóvenes de eucaliptos. La planta responde formando agallas, que causan enrollamiento, defoliación y colapso de brotes, afectando seriamente la producción. En este trabajo se analizan los cambios morfogenéticos y anatómicos provocados por el desarrollo de las agallas, comparándolos con plantas sanas. Con técnicas tradicionales de microscopía óptica y electrónica de barrido se estudiaron ejemplares de Eucalyptus grandis y E. camaldulensis, cultivados en Corrientes, Argentina. La avispa ovipone entre los haces vasculares, el vegetal produce un tejido hiperplásico que se diferencia en cuatro estratos: nutricio, esclerosado, tanífero y cristalífero. El recorrido de los tejidos vasculares se obstruye, produciéndose “bucles xilemáticos” que interrumpen el flujo normal de agua y fotosintatos. Analizando los cambios morfológicos y anatómicos, junto al desarrollo del insecto, se divide el ciclo en tres etapas. Este trabajo demuestra que la formación de agallas en Eucalyptus representa un excelente ejemplo de fenotipo extendido, donde la acción de L. invasa induce al crecimiento anormal de los tejidos vegetales, tanto en aumento del número de células, colapso del sistema vascular de la zona afectada y aparición de nuevas características anatómicas.

New Record of Insect Pests on Seedlings of Eucalyptus

The present paper reports the occurrence of insects damaging Eucalyptus in nursery stage. Out of nine insects recorded, seven species observed as occasional defoliating species, viz. Achaea janata (Linnaeus) (Lepidoptera : Noctuidae), Catapsilia crocale Cramer (Lepidoptera : Pieridae), Dasychira grotei Moore (Lepidoptera : Lymantriidae), Eurema hecabe Linnaeus (Lepidoptera : Pieridae), Hyposidra talaca (Walker) (Lepidoptera : Geometridae), Lymantria sobrina Moore (Lepidoptera : Lymantriidae) and Spodoptera litura (Fabricius) (Lepidoptera : Noctuidae), one rare sap-sucking species, Chrysocoris purpureus Westwood (Heteroptera : Pentatomodae) and one gall making species, Leptocybe invasa Fisher &amp; LaSalle (Hymenoptera : Eulophidae). Among the nine species collected, six defoliators and one sap sucker are new addition to the Eucalyptus entomology. Further, H. talaca is the first record of occurrence on Eucalyptus in India. On the basis of percentage infestation/damage caused by above insects, L. invasa, commonly known as blue gum chalcid wasp, was recorded only as a key insect pest in nursery stage of Eucalyptus. The results have been discussed in the light of the present observations.