Parasitoid polydnaviruses: evolution,pathology and applications

One of the more unusual groups of insect pathogens consists of members of the family Polydnaviridae, insect DNA viruses that live in mutual symbioses with their associated parasitoid wasp (Hymentoptera) carriers until they are injected into specific lepidopteran hosts. Once inside this secondary host, polydnaviruses cause a wide variety of negative effects that ultimately ensure the survival of the parasitoid larvae. Because of their unusual life strategy and genetic features, it had been difficult to fully characterise polydnaviruses in terms of evolutionary history, replication cycle and functions in the host that might normally be well characterised for more conventional viruses. Recently, our understanding of polydnavirus evolutionary origins, gene content, genome organisation and functions in parasitism has greatly increased. Key findings are summarised in this review with emphasis on evolution of polydnavirus genes and genomes, their functional roles in insect pathology and their potential applications in insect biological control and biotechnology.     

A large-scale gene discovery for the red palm weevil Rhynchophorus ferrugineus （Coleoptera： Curculionidae）

The red palm weevil （RPW; Rhynchophorusferrugineus） is a devastating pest of palms, prevalent in the Middle East as well as many other regions of the world. Here, we report a large-scale de novo complementary DNA （cDNA） sequencing effort that acquired ~5 million reads and assembled them into 26 765 contigs from 12 libraries made from samples of different RPW developmental stages based on the Roche/454 GS FLX platform. We annotated these contigs based on the publically available known insect genes and the Tribolium castaneum genome assembly. We find that over 80% of coding sequences （CDS） from the RPW contigs have high-identity homologs to known proteins with complete CDS. Gene expression analysis shows that the pupa and larval stages have the highest and lowest expression levels, respectively. In addition, we also identified more than 60 000 single nucleotide polymorphisms and 1 200 simple sequence repeat markers. This study provides the first large-scale eDNA dataset for RPW, a much-needed resource for future molecular studies.     

Endophytic bacterium,Bacillus amyloliquefaciens,enhances ornamental hosta resistance to diseases and insect pests

A total of 84 bacterial endophytes were isolated from seeds of 6 cultivars of ornamental hostas, and they were identified to 5 species based on morphological characteristics and 16S rDNA sequence analysis. Among them, the strain ‘Blu-v2’, which was isolated from the seeds of cultivar ‘Blue Umbrella’ and identified to be Bacillus amyloliquefaciens, showed highest antifungal activity and capacity to deter feeding by Fall armyworms (Spodoptera fruigiperda). Lipopeptides in cultures of Blu-v2 were determined using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and its antifungal activities were verified. However, the lipopeptide preparation did not show toxicity to larvae of Fall armyworms. In a greenhouse experiment, Blu-v2 was inoculated into small plantlets of hosta (cultivar ‘Rainforest Sunrise’). The leaves of plants with bacteria (endophyte-infected?=?E+) and without bacteria (endophyte-free?=?E?) were used in seven-day feeding experiments employing fourth-instar larvae of Fall armyworms. We found that there was a significant decrease in the weights of larvae fed with E+ compared to E? plants; and the mortality rate of larvae fed with E? leaves was lower (3.33%) compared to that of larvae fed with E+ leaves (30%). Based on our studies, we suggest that endophytic B. amyloliquefaciens strain Blu-v2 has potential value as a biocontrol agent to reduce damage from fungal diseases and insect pests of hosta cultivars.     

广东国兰虫害发生调查

2009年12月至2013年3月,调查了广东省国兰虫害种类及其危害,调查结果表明：在广东为害国兰的节肢动物有：半翅目的牡蛎蚧Lepidosaphinae、褐软蜡蚧Coccus hesperidum (Linnaeus)和蚜虫Aphidae、缨翅目的兰花蓟马Dichromothrips corbetti (Priesner)、直翅目的Locustoidea、螽斯Tettigoniidae、鳞翅目的蓑蛾Psychidae以及软体动物蜗牛和蛞蝓等9种（类）有害生物,并对国兰虫害的为害状和发生情况进行了简要描述,以期为国兰虫害的诊断和预防提供指导。     

Comparison of three transgenic Bt rice lines for insecticidal protein expression and resistance against a target pest,Chilo suppressalis (Lepidoptera: Crambidae)

Two transgenic rice lines (T2A‐1 and T1C‐19b) expressing cry2A and cry1C genes, respectively, were developed in China, targeting lepidopteran pests including Chilo suppressalis (Walker) (Lepidoptera: Crambidae). The seasonal expression of Cry proteins in different tissues of the rice lines and their resistance to C. suppressalis were assessed in comparison to a Bt rice line expressing a cry1Ab/Ac fusion gene, Huahui 1, which has been granted a biosafety certificate. In general, levels of Cry proteins were T2A‐1 > Huahui 1 > T1C‐19b among rice lines, and leaf > stem > root among rice tissues. The expression patterns of Cry protein in the rice line plants were similar: higher level at early stages than at later stages with an exception that high Cry1C level in T1C‐19b stems at the maturing stage. The bioassay results revealed that the three transgenic rice lines exhibited significantly high resistance against C. suppressalis larvae throughout the rice growing season. According to Cry protein levels in rice tissues, the raw and corrected mortalities of C. suppressalis caused by each Bt rice line were the highest in the seedling and declined through the jointing stage with an exception for T1C‐19b providing an excellent performance at the maturing stage. By comparison, T1C‐19b exhibited more stable and greater resistance to C. suppressalis larvae than T2A‐1, being close to Huahui 1. The results suggest cry1C is an ideal Bt gene for plant transformation for lepidopteran pest control, and T1C‐19b is a promising Bt rice line for commercial use for tolerating lepidopteran rice pests.     

Long‐term response of temperate canopy trees to removal of browsing from an invasive arboreal herbivore in New Zealand

Defoliation of forest tree canopies by herbivores and other agents, leading to tree mortality and reduced productivity, threatens the ecological stability of forests globally. This study shows that long‐term control of a mammalian arboreal folivore (brushtail possums; Trichosurus vulpecula Phalangeridae) reduces crown dieback and increases foliage cover in browsing‐damaged canopy trees. We monitored indices of possum density, possum browsing, tree foliage cover and crown dieback for 20 years following initiation of possum control in 1994 that repeatedly reduced possum densities to near zero every 5–6 years and kept the population below 35% of pre‐control levels over the entire period. Observable possum browsing was recorded on 20–49% of individuals of three palatable tree species at the time of first control. Those percentages fell to zero after control and never exceeded 2–10% for individual species over the next 19 years. We recorded significant increases in foliage cover attributable to recovery from defoliation by possums for all three species during the first 10 years. Large increases in foliage cover occurred on individuals that were heavily browsed in 1994 (mean increases: 36–89%), but mean population increases were modest (3–19%) because only 10–19% of trees were initially heavily browsed. Twenty‐year mortality rates were similar for plants with, or without, initial possum browsing, indicating no residual impact of pre‐control browsing on tree mortality. Times for full recovery of crown foliage cover varied from 10 years for the youngest trees and faster growing species to more than 20 years for mature individuals of the slowest growing species.     

Insect distribution in response to climate change based on a model: Review of function and use of CLIMEX

The significant dependence of agricultural productivity on pest control requires pest distribution predictions at an early stage of pest invasion. Because pest cycles are critically affected by climate, climate is one of the most important factors for predicting an invasive pest. CLIMEX is a highly effective tool that can predict potential geographical species distributions, and test the regional suitability for a target species' habitat based on data including climate change scenarios. CLIMEX has been recently used in Europe, North America, China and Australia, among others. However, for modeling species distributions in Korea, the use of the model has been limited to date. This study aimed to first introduce the function and application of CLIMEX by reviewing important studies using this model. Second, we investigated previous studies using the model simulation to demonstrate the practical applicability of CLIMEX for the agricultural sector, and its use in forecasting.     

Cross-correlation analysis of invasive mango mealybug and its associated natural enemies in relation to meteorological factors: implications for biological control

Damage caused by invasive downey snow line mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae) has been reported to vary between 30% to complete crop loss where no control measure is applied. The current studies seek to determine factors influencing R. iceryoides population outbreaks, parasitoid – host and predator–prey relationships as well as predict optimal management strategies through weather modelling over a period of 28 months from 2008 to 2010 in Tanzania. The highest incidence of R. iceryoides was recorded during the dry season coinciding with the major mango fruiting season. The relationship between R. iceryoides and the parasitoid was positive but not significant, which implies the influence on outbreaks was negligible probably due to low percent parasitism (<12%). However, the predator abundance was directly and significantly related to that of R. iceryoides. Average temperature, average relative humidity, rainfall, and R. iceryoides abundance were autocorrelated to each other. Cross-correlation coef?cients vary significantly from ?0.286 to 0.589 for the pair-variable between R. iceryoides, temperature, relative humidity, rainfall, parasitism and predators. Our findings showed that temperature was the key climatic variable that significantly influenced R. iceryoides outbreaks while rainfall was significantly negatively associated with the pest. Time series analyses show R. iceryoides population increased 4 months after an increase in average temperature in all the sites, 11 months after rainfall and 11 months after relative humidity in Kibaha and Dar es Salaam, respectively. Our findings revealed that R. iceryoides is an excellent target for classical biological control. Thus, the importation of promising co-evolved parasitoid specific to R. iceryoides from the aboriginal home is crucial in formulating an efficient and sustainable management approaches against the invasive mealybug pest in mango agro-ecosystems.     

Temperature‐dependent development of the double‐spined spruce bark beetle Ips duplicatus (Sahlberg, 1836) (Coleoptera; Curculionidae)

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