Susceptibility of Rubus Species and Cultivars to Blackberry Leaf Rust (Phragmidium violaceum) and its Control by Fungicides

Rubus cultivars were compared with R. procerus for their susceptibility to Phragmidium violaceum, a pathogen first recorded in Victoria in February 1984, by inoculation of detached leaflets in the laboratory. The cultivar ‘Thornless Evergreen’ was highly susceptible. Cultivars ‘Thornfree’, ‘Dirksen Thornless’ and ‘Smoothstem’ were moderately susceptible whilst cvs ‘Silvan’ and ‘Lawtonberry’ were resistant. Cultivars ‘Cherokee’, ‘Cheyenne’, ‘Comanche’, ‘Marionberry’, ‘Boysenberry’, ‘Youngberry’, and ‘Olallie’ were highly resistant. ‘Loganberry’ and the raspberry cv. ‘Malling Landmark’ were immune. Seven fungicides were evaluated for their effect on P. violaceum. Mancozeb and triforine were the most effective against spore germination in vitro. RH 3866, triforine, propiconazole and mancozeb were the most effective in protective tests on detached leaflets of R. procerus, while RH 3866, propiconazole and flutriafol were the most effective in similar, curative tests. Phytotoxicity on detached leaflets was severe at high concentrations of triadimefon and propiconazole, and moderate to slight at similar concentrations of RH 3866 and copper hydroxide.     

The collection and selection in Europe of isolates of Phragmidium violaceum (Uredinales) pathogenic to species of European blackberry naturalised in Australia

Phragmidium violaceum is a rust fungus with potential for the biological control of European blackberry (Rubus fruticosus) in Australia. The collection, selection, purification and multiplication in Europe of isolates of the rust is described. Species of European blackberry naturalised in Australia showed different levels of susceptibility when inoculated with a pool of 15 isolates highly pathogenic to Rubus procerus. Selection of individual isolates on the four most widespread blackberry species showed that only two of the isolates would be required to obtain the best attack on these four species.     

Mitochondrial and Nuclear Gene Dynamics of Introduced Populations of Lepomis Macrochirus

A population of bluegill sunfish, Lepomis macrochirus, was introduced into three man-made ponds in 1966. Analyses of these ponds in 1984 and 1985 found significant mtDNA divergence without nuclear gene differentiation. The difference between nuclear gene and mtDNA measures of interpopulational divergence was very large and suggests that sexual asymmetries in life histories may be important considerations in mtDNA and nuclear gene rates of divergence. The rapid divergence of mtDNA haplotype frequencies suggests that sorting of previously existing variation may accelerate mtDNA divergence among recently isolated populations.     

Invaded range of the blackberry pathogen Phragmidium violaceum in the Pacific Northwest of the USA and the search for its provenance

Field surveys in 2006 confirmed that the exotic rust fungus Phragmidium violaceum was widespread on Rubus armeniacus and Rubus laciniatus in the Pacific Northwest of the USA. The origin and dispersal pattern of this obligate biotrophic pathogen in the USA were investigated by comparing the genetic diversity and structure of 27 isolates each from the USA and Europe, and 20 isolates from Australia where an invasion occurred in 1984. Analysis of 11 microsatellite loci revealed 74 unique genotypes, with the European population having a significantly higher level of allelic diversity and number of private alleles compared to populations from the USA and Australia. Principal coordinate analysis (PCA), analysis of molecular variance and pairwise comparisons of Φ confirmed a strong level of differentiation among continental populations, with little divergence between isolates from the USA and Europe, but a high level of differentiation between these isolates and those from Australia. These results were broadly supported by the Bayesian cluster analysis, which indicated that at K = 3 the clustering of the isolates corresponds to their geographic origin. Bayesian clustering, PCA as well as insignificant migration estimates from Europe to the USA suggest that the USA population is not a direct descendant from the European P. violaceum population. There was a weak association between genetic and geographic distance among the USA isolates, suggesting invasion was initially localized prior to dispersal or that the population may have been present for some time prior to first detection in 2005.     

Genome-Wide Variation of Cytosine Modifications Between European and African Populations and the Implications for Complex Traits

Elucidating cytosine modification differences between human populations can enhance our understanding of ethnic specificity in complex traits. In this study, cytosine modification levels in 133 HapMap lymphoblastoid cell lines derived from individuals of European or African ancestry were profiled using the Illumina HumanMethylation450 BeadChip. Approximately 13% of the analyzed CpG sites showed differential modification between the two populations at a false discovery rate of 1%. The CpG sites with greater modification levels in European descent were enriched in the proximal regulatory regions, while those greater in African descent were biased toward gene bodies. More than half of the detected population-specific cytosine modifications could be explained primarily by local genetic variation. In addition, a substantial proportion of local modification quantitative trait loci exhibited population-specific effects, suggesting that genetic epistasis and/or genotype × environment interactions could be common. Distinct correlations were observed between gene expression levels and cytosine modifications in proximal regions and gene bodies, suggesting epigenetic regulation of interindividual expression variation. Furthermore, quantitative trait loci associated with population-specific modifications can be colocalized with expression quantitative trait loci and single nucleotide polymorphisms previously identified for complex traits with known racial disparities. Our findings revealed abundant population-specific cytosine modifications and the underlying genetic basis, as well as the relatively independent contribution of genetic and epigenetic variations to population differences in gene expression.     

The Functional Response of Parasitoids and its Implications for Biological Control

The parasitoid functional response is regarded as central to host-parasitoid dynamics. If so, then the shape of this response may be related to parasitoid success in biological control programmes. We test this by reviewing the literature on the functional response together with the BIOCAT database. Only 32 out of 94 papers have dealt experimentally with the functional response of parasitoids used in biocontrol. The study suggests that most parasitoid species have a type II response. Also, there is no clear relationship between curve shape and success in control. We conclude that other aspects of the parasitoid behaviour deserve more attention in order to understand and predict these insects' success as control agents.     

原始生物大分子动态的数学模型及其进化意义

本文应用生态学上关于种群增长及种间竞争的逻辑斯缔方程,提出原始生物大分子动态的数学模型,对从该模型推导得的几种可能结果进行了分析,得出在生命起源初期的原始生物圈的生物多样性是很低的结论,即原始生物圈中较大量存在的只是一些种类单一的,可复制的原始生物大分子,因此,可以认为生物进化就是建立在这样的一个基础上,并沿着生物多样性不断提高的途径演化,该模型还有助于对广泛存在于现代生物基因组中的重复序列的起源的认识。     

Dynamics of Foliage and Thatch Populations of Introduced Pseudomonas fluorescens and Streptomyces sp. on a Fairway Turf

Populations of bacteria (Pseudomonas fluorescens A506 and Streptomyces sp. strain 93) applied to a creeping bentgrass/annual bluegrass fairway turf were followed over time on leaves and thatch. While introduced populations remained at detectable levels over a period of 11–25 days, they usually declined gradually and did not increase after their application to turf. Streptomyces rapidly disappeared from leaves while P. fluorescens was able to maintain similar population sizes on both thatch and leaves, after an initial decline of about 1-log unit, showing that it was actively colonizing the foliage despite loss of biomass from lawn mowing. Throughout these experiments, populations of indigenous microbes on foliage and thatch remained stable, about 10⁶ and 10⁸ cfu g⁻¹ for fungi and bacteria, respectively, and were not affected by the application of bacterial antagonists. Niche-clearing with hydrogen peroxide, which temporarily reduced the population size of indigenous microorganisms two-fold, caused population size of P. fluorescens to increase approximately ten-fold within 24 h, while it declined by about one log unit on untreated turf. It is concluded that the indigenous microflora competes with introduced bacterial antagonists and interferes with their establishment and persistence on turf. Additional studies with P. fluorescens revealed that its population size was inoculum dose-dependent and that solid top dressing was slightly more efficient than spraying liquid suspension in establishing the antagonist. It was possible to maintain P. fluorescens populations above 10⁵ cfu/g of thatch and leaves for 2 weeks or more with both top-dressing or spraying with about 1 to 3 × 10¹⁰ cfu m⁻².     

Establishment, Spread and Initial Impact of Aphis chloris Koch (Hemiptera: Aphididae), Introduced into Australia for the Biological Control of St John's Wort

The aphid, Aphis chloris Koch, quickly established following field release at numerous sites throughout south-eastern Australia. Local populations built up to levels at which migratory alates were produced within the first season. Dispersal of these alates over large distances led to widespread colonization of St John's wort infested areas within 2-3 years. Detailed observations at the primary release site at Pierce's Creek, ACT, showed that aphid populations undergo a seasonal cycle of population growth throughout the summer, followed by a migratory phase with alate production and dispersal in autumn and a population decline over winter. This pattern was repeated at other release sites monitored over a 5-year period from 1987 to 1991 inclusive, without populations building up to damaging levels. Natural enemies, competition from existing biological control agents, climatic factors and emigration appear sufficient to limit such outbreaks. While caged plants did show a decline in vigour and seed production under heavy aphid attack, such damage was intermittent in open field situations. The present study suggests that, while A. chloris is now widespread, it will not make an important contribution to the overall control of St John's wort.     

European Origin of Bradyrhizobium Populations Infecting Lupins and Serradella in Soils of Western Australia and South Africa

We applied a multilocus phylogenetic approach to elucidate the origin of serradella and lupin Bradyrhizobium strains that persist in soils of Western Australia and South Africa. The selected strains belonged to different randomly amplified polymorphic DNA (RAPD)-PCR clusters that were distinct from RAPD clusters of applied inoculant strains. Phylogenetic analyses were performed with nodulation genes (nodA, nodZ, nolL, noeI), housekeeping genes (dnaK, recA, glnII, atpD), and 16S-23S rRNA intergenic transcribed spacer sequences. Housekeeping gene phylogenies revealed that all serradella and Lupinus cosentinii isolates from Western Australia and three of five South African narrow-leaf lupin strains were intermingled with the strains of Bradyrhizobium canariense, forming a well supported branch on each of the trees. All nodA gene sequences of the lupin and serradella bradyrhizobia formed a single branch, referred to as clade II, together with the sequences of other lupin and serradella strains. Similar patterns were detected in nodZ and nolL trees. In contrast, nodA sequences of the strains isolated from native Australian legumes formed either a new branch called clade IV or belonged to clade I or III, whereas their nonsymbiotic genes grouped outside the B. canariense branch. These data suggest that the lupin and serradella strains, including the strains from uncultivated L.cosentinii plants, are descendants of strains that most likely were brought from Europe accidentally with lupin and serradella seeds. The observed dominance of B. canariense strains may be related to this species' adaptation to acid soils common in Western Australia and South Africa and, presumably, to their intrinsic ability to compete for nodulation of lupins and serradella.     

Population Dynamics of Owned,Free-Roaming Dogs: Implications for Rabies Control

Background

Rabies is a serious yet neglected public health threat in resource-limited communities in Africa, where the virus is maintained in populations of owned, free-roaming domestic dogs. Rabies elimination can be achieved through the mass vaccination of dogs, but maintaining the critical threshold of vaccination coverage for herd immunity in these populations is hampered by their rapid turnover. Knowledge of the population dynamics of free-roaming dog populations can inform effective planning and implementation of mass dog vaccination campaigns to control rabies.

Methodology/Principal Findings

We implemented a health and demographic surveillance system in dogs that monitored the entire owned dog population within a defined geographic area in a community in Mpumalanga Province, South Africa. We quantified demographic rates over a 24-month period, from 1^st January 2012 through 1^st January 2014, and assessed their implications for rabies control by simulating the decline in vaccination coverage over time. During this period, the population declined by 10%. Annual population growth rates were +18.6% in 2012 and -24.5% in 2013. Crude annual birth rates (per 1,000 dog-years of observation) were 451 in 2012 and 313 in 2013. Crude annual death rates were 406 in 2012 and 568 in 2013. Females suffered a significantly higher mortality rate in 2013 than males (mortality rate ratio [MRR] = 1.54, 95% CI = 1.28–1.85). In the age class 0–3 months, the mortality rate of dogs vaccinated against rabies was significantly lower than that of unvaccinated dogs (2012: MRR = 0.11, 95% CI = 0.05–0.21; 2013: MRR = 0.31, 95% CI = 0.11–0.69). The results of the simulation showed that achieving a 70% vaccination coverage during annual campaigns would maintain coverage above the critical threshold for at least 12 months.

Conclusions and Significance

Our findings provide an evidence base for the World Health Organization’s empirically-derived target of 70% vaccination coverage during annual campaigns. Achieving this will be effective even in highly dynamic populations with extremely high growth rates and rapid turnover. This increases confidence in the feasibility of dog rabies elimination in Africa through mass vaccination.     

Dynamics of Baculovirus Growth and Dispersal in Mamestra brassicae L. (LepidopteraNoctuidae) Larval Populations Introduced into Small Cabbage Plots

The nuclear polyhedrosis virus of Mamestra brassicae has been studied in larval populations of the moth introduced into small plots of cabbages. Primary dispersal of virus from single foci of infected larvae resulted from enhanced movement of the larvae, which colonized new plants logarithmically. Virus growth within the host population was quantified, and infection of young larvae in the following generation was related directly to the concentration of virus produced during the primary phase. Secondary cycling of virus resulted in dispersal of inoculum from multiple foci, and a large proportion of plants were ultimately colonized by infected larvae. The dynamics of virus growth during secondary dispersal were quantified and contrasted with results from the primary phase. The significance of these results is discussed in relation to possible control of insect pests through dispersal of virus by the host insect.     

Interactions Between Entomopathogenic Fungi and Other Natural Enemies: Implications for Biological Control

Pathogens and arthropod natural enemies may contribute to the suppression of insect pest populations either as individual species or as species complexes. However, because natural enemies of insects have evolved and function in a multitrophic context it is important to assess interactions within complexes of natural enemies if they are to be exploited effectively in pest management. Natural enemies can interact either synergistically/additively (e.g. enhanced transmission and dispersal of insect pathogens) or antagonistically (e.g. parasitism/infection, predation and competition). In this paper, studies assessing the potential interactions between insect and fungal natural enemies are reviewed. In general, these studies indicate the positive nature of the interactions between arthropod natural enemies and fungal pathogens with respect to the control of insect populations. More work is required to investigate further the many ways in which the natural enemy community interacts in the agroecosystem     

Population Dynamics and Potential for Biological Control of an Exotic Invasive Shrub in Hawaiian Rainforests

Introduction of biological control agents to reduce the abundance of exotic invasive plant species is often considered necessary but risky. I used matrix projection models to investigate the current population dynamics of Clidemia hirta (Melastomataceae), an invasive shrub, in two rainforest stands on the island of Hawaii and to predict the efficacy of hypothetical biological control agents in reducing population growth rates. Stage-structured matrix models were parameterized with field data collected over 3 years from 2906 C. hirta plants in a recently invaded forest with an open overstory (Laupahoehoe) and 600 plants in a less recently invaded forest with a closed canopy (Waiakea). Asymptotic population growth rates (λ) for both populations in all years were greater than one, demonstrating that both populations were growing. Composite elasticities were high for the seedling life-history stage and fecundity, and near-term demographic elasticities suggested that changes in seedling survival would have the largest effect on population size in the short term. However, simulations showed that almost 100% of seedlings or new recruits produced per reproductive adult would have to be destroyed to cause populations to go locally extinct under current environmental conditions. Herbivores or pathogens that decrease survival across all vegetative stages by 12% at Waiakea and 64% at Laupahoehoe were projected to cause the populations to decline. Thus, biocontrol agents that reduce survival of multiple life-history stages rather than seed production should be pursued to control C. hirta in Hawaiian rainforests.     

Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control

Background

Triatoma infestans —the principal vector of the infection that causes Chagas disease— defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign.

Methodology and Principal Findings

We measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate.

Conclusions and Significance

Chicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies.     

Selective Medium for Recovering Specific Populations of Rhizobia Introduced into Tropical Soils

Experiments were designed to evaluate the usefulness of antifungal agents and streptomycin for recovering low densities of rhizobia inoculated into tropical soils. The results showed that yeast-mannitol agar (pH 6.0) containing 500 μg of streptomycin, 400 μg of cycloheximide and 50 μg of benomyl or chlorothalonil per ml was the best selective medium.     

两种濒危水韭植物迁地保护居群的基因流动态及回归重建保育遗传管理策略

采用微卫星分子标记对中华水韭（Isoetessinensis）安徽休宁、浙江建德和东方水韭（I.orientalis）浙江松阳三个孑遗居群的迁地保护居群开展了遗传多样性检测与遗传结构分析。7对多态性微卫星引物在36个迁地保护亚居群的720个样本中共检测到59个等位基因,每位点平均等位基因数（A）为8·43。迁地保护亚居群均维持很高的遗传多样性,多态信息含量（PIC）平均为0·707。迁地保护亚居群间遗传分化较低,遗传分化系数GST仅为0·070,居群间具有较大基因流（Nm=3·59）。单因素方差分析发现水韭孢子或孢子体在沿主要水流方向上的长距离传播能力要强于弱水流方向上的短距离传播能力,水流动态对水韭植物的基因流有重要影响。这与UPGMA聚类分析中迁地保护亚居群按邻近位置或水流相通程度优先聚类的结果相一致,水流所带动的强大基因流导致了不同孑遗居群来源的迁地保护亚居群间的遗传混杂。建议在开展水韭植物的迁地保护或回归自然重建时,对具有地方适应分化或者显著性进化的水韭植物居群应相互隔离而不宜配置在一起,以避免远交衰退的遗传风险。