Identification of the causal agent of Botryosphaeria stem canker in Ethiopian Eucalyptus plantations

Plantations of exotic Eucalyptus make up more than 30% of Ethiopia's plantations, providing fuel and construction timber to the country. Species such as E. camaldulensis, E. saligna, E. grandis, E. citriodora and E. globulus are most commonly planted. During a survey of Eucalyptus diseases in 2000 and 2001, Botryosphaeria stem canker was observed in most plantations. The disease symptoms included tip die- back, coppice failure and stem cankers characterised by kino exudation. The aim of this study was to identify the species responsible for Botryosphaeria stem canker in Ethiopia. Culture and conidial morphology, as well as DNA-based identification involving Restriction Fragment Length Polymorphisms (RFLPs) and sequencing of the Internal Transcribed Spacer regions (ITS) of the ribosomal RNA gene and the elongation factor 1-alpha (EF1-α) gene, were used to identify isolates. Pathogenicity studies were conducted in the greenhouse and under field conditions. Results showed that Botryosphaeria parva is responsible for Botryosphaeria stem canker of Eucalyptus in Ethiopia. This is the first report of the fungus from this country. Greenhouse and field inoculation studies showed that the Ethiopian isolates are highly virulent. Careful site species selection and breeding trials are thus needed to reduce the impact of this disease in Ethiopia

Tree invasions and biosecurity: eco-evolutionary dynamics of hitchhiking fungi

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Botanical gardens as key resources and hazards for biosecurity

Biodiversity and economic losses resulting from invasive plant pests and pathogens are increasing globally. For these impacts and threats to be managed effectively, appropriate methods of surveillance, detection and identification are required. Botanical gardens provide a unique opportunity for biosecurity as they accommodate diverse collections of exotic and native plant species. These gardens are also often located close to high-risk sites of accidental invasions such as ports and urban areas. This, coupled with routine activities such as the movement of plants and plant material, and visits by millions of people each year, place botanical gardens at risk to the arrival and establishment of pests and pathogens. Consequently, botanical gardens can pose substantial biosecurity risks to the environment, by acting as bridgeheads for pest and pathogen invasions. Here we review the role of botanical gardens in biosecurity on a global scale. The role of botanical gardens has changed over time. Initially, they were established as physic gardens (gardens with medicinal plants), and their links with academic institutions led to their crucial role in the accumulation and dissemination of botanical knowledge. During the second half of the 20th century, botanical gardens developed a strong focus on plant conservation, and in recent years there has been a growing acknowledgement of their value in biosecurity research as sentinel sites to identify pest and pathogen risks (novel pest-host associations); for early detection and eradication of pests and pathogens; and for host range studies. We identify eight specific biosecurity hazards associated with botanical gardens and note potential management interventions and the opportunities these provide for improving biosecurity. We highlight the value of botanical gardens for biosecurity and plant health research in general, and the need for strategic thinking, resources, and capacity development to make them models for best practices in plant health

Identification of the sex pheromone of the tree infesting Cossid Moth Coryphodema tristis (Lepidoptera: Cossidae)

The cossid moth (Coryphodema tristis) has a broad range of native tree hosts in South Africa. The moth recently moved into non-native Eucalyptus plantations in South Africa, on which it now causes significant damage. Here we investigate the chemicals involved in pheromone communication between the sexes of this moth in order to better understand its ecology, and with a view to potentially develop management tools for it. In particular, we characterize female gland extracts and headspace samples through coupled gas chromatography electro-antennographic detection (GC-EAD) and two dimensional gas chromatography mass spectrometry (GCxGC-MS). Tentative identities of the potential pheromone compounds were confirmed by comparing both retention time and mass spectra with authentic standards. Two electrophysiologically active pheromone compounds, tetradecyl acetate (14:OAc) and Z9-tetradecenyl acetate (Z9-14:OAc) were identified from pheromone gland extracts, and an additional compound (Z9-14:OH) from headspace samples. We further determined dose response curves for the identified compounds and six other structurally similar compounds that are common to the order Cossidae. Male antennae showed superior sensitivity toward Z9-14:OAc, Z7-tetradecenyl acetate (Z7-14:OAc), E9-tetradecenyl acetate (E9-14:OAc), Z9-tetradecenol (Z9-14:OH) and Z9-tetradecenal (Z9-14:Ald) when compared to female antennae. While we could show electrophysiological responses to single pheromone compounds, behavioral attraction of males was dependent on the synergistic effect of at least two of these compounds. Signal specificity is shown to be gained through pheromone blends. A field trial showed that a significant number of males were caught only in traps baited with a combination of Z9-14:OAc (circa 95 of the ratio) and Z9-14:OH. Addition of 14:OAc to this mixture also improved the number of males caught, although not significantly. This study represents a major step towards developing a useful attractant to be used in management tools for C. tristis and contributes to the understanding of chemical communication and biology of this group of insects

Diversity and distribution of co-infecting Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum in South Africa

Species in the fungal family Botryosphaeriaceae are latent pathogens on woody trees. These fungi often have a wide host range, which can include native and introduced hosts in an area. Multi-locus DNA sequence identification on a recent collection of Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum trees in South Africa revealed cross-infectivity of several species, novel host associations and new country reports. Neofusicoccum eucalyptorum, Neofusicoccum kwambonambiense, Neofusicoccum parvum, Neofusicoccum australe and Lasiodiplodia pseudotheobromae were identified from both tree species, with L. pseudotheobromae and N. eucalyptorum isolated for the first time from S. cordatum, similar to N. kwambonambiense from Eucalyptus. This also represents the first report of L. pseudotheobromae from South Africa. Botryosphaeriaceae species on Eucalyptus species and S. cordatum are fairly well known from South Africa. However, this study revealed new associations, indicating that conclusions should not be generalized and that more intensive sampling from different areas and over time is likely to reveal distinct species and host association patterns.The National Research Foundation (NRF), members of the Tree Protection Co-operative Programme (TPCP) and the Department of Science and Technology (DST)/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), South Africa. Open Access funded by SAAB.http://www.elsevier.com/locate/sajbhb2016Forestry and Agricultural Biotechnology Institute (FABI)Genetic

Complex patterns of global spread in invasive insects: eco-evolutionary and management consequences

The advent of simple and affordable tools for molecular identification of novel insect invaders and assessment of population diversity has changed the face of invasion biology in recent years. The widespread application of these tools has brought with it an emerging understanding that patterns in biogeography, introduction history and subsequent movement and spread of many invasive alien insects are far more complex than previously thought. We reviewed the literature and found that for a number of invasive insects, there is strong and growing evidence that multiple introductions, complex global movement, and population admixture in the invaded range are commonplace. Additionally, historical paradigms related to species and strain identities and origins of common invaders are in many cases being challenged. This has major consequences for our understanding of basic biology and ecology of invasive insects and impacts quarantine, management and biocontrol programs. In addition, we found that founder effects rarely limit fitness in invasive insects and may benefit populations (by purging harmful alleles or increasing additive genetic variance). Also, while phenotypic plasticity appears important post-establishment, genetic diversity in invasive insects is often higher than expected and increases over time via multiple introductions. Further, connectivity among disjunct regions of global invasive ranges is generally far higher than expected and is often asymmetric, with some populations contributing disproportionately to global spread. We argue that the role of connectivity in driving the ecology and evolution of introduced species with multiple invasive ranges has been historically underestimated and that such species are often best understood in a global context

Fungal Genomics Challenges the Dogma of Name-Based Biosecurity

Microorganisms have inadvertently been spread via the global movement and trade of their substrates, such as animals, plants, and soil. This intercontinental exchange in the current era of globalisation has given rise to significant increases in the distribution of known pests and pathogens. Importantly, it has also resulted in many novel, emerging, infectious diseases. Biosecurity and quarantine, which aim to prevent the establishment of foreign or harmful organisms in a non-native area, are under significant pressure due to the massive increases in travel and trade. Traditionally, quarantine regulations have been implemented based on pathogens that already cause significant disease problems on congener hosts in other parts of the world (e.g., Q-bank, available at http://www.q-bank.eu). Well-known pathogens are described, named, and studied to determine their disease cycle, epidemiology, and impact. Their importance is assessed based on their risk of infection, establishment, and economic or environmental consequences. This then shapes phytosanitary practices.The Tree Protection Co-operative Programme (TPCP), THRIP initiative of the Department of Trade and Industry, Department of Science and Technology (DST)/ National Research Foundation (NRF), and Centre of Excellence in Tree Health Biotechnology (CTHB).http://www.plospathogens.orgam2016Forestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyPlant Scienc

Development and characterisation of microsatellite markers for the fungus Lasiodiploidia theobromae

Abstract in Portuguese and English Title in Portugese: Desenvolvimento e caracterização de marcadores microsatélites para o fungo Lasiodiplodia theobromaeLasiodiplodia theobromae is an important fungal pathogen of higher plants from tropical and sub-tropical regions. The fungus infects divergent hosts in a wide range of environmental conditions, suggesting that it is highly variable. The aim of this study was to develop new polymorphic microsatellite markers from a Brazilian isolate of L. theobromae that can be used in population studies of this and related fungi. The nine microsatellite markers developed included six that revealed allelic polymorphisms among nine isolates of the disease collected from infected plants in Brazil. Preliminary evaluation of the markers suggested substantial genetic variability among Brazilian L. theobromae populations. These markers have potential utility for evolutionary and epidemiologic studies of this fungus.José Emilson Cardoso and Michael James Wilkinso

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

Increased rates of movement and the accumulation of insects establishing outside their native range is leading to the ‘global homogenization’ of agricultural and forestry pests. We use an invasive wasp, Leptocybe invasa (Hymenoptera: Eulophidae), as a case study to highlight the rapid and complex nature of these global invasions and how they can complicate management options. To trace the invasion history of L. invasa globally, we characterised the genetic diversity within and between populations from its origin and invaded regions using mitochondrial and nuclear markers. Three mitochondrial Haplogroups were identified, of which two are likely different species that appear to have been independently introduced into different parts of the world. One type (Mitochondrial Haplogroup 1) occurs globally, and is the exclusive type found in Europe, the Middle East, South America and most of Africa. The second type (Mitochondrial Haplogroup 2) co-occurs with the first-type in Laos, South Africa, Thailand and Vietnam, while a third type (Mitochondrial Haplogroup 3) occurs exclusively in Australia, its native range. The distinction of the two invasive Haplogroups was supported by analysis of newly developed simple sequence repeat (microsatellite) markers in populations from 13 countries. Further analyses using clustering methods and approximate Bayesian computation suggested the occurrence of hybridisation in the Laos population and revealed that an unsampled population was the origin of Mitochondrial Haplogroup 1. The analyses also showed little genetic differentiation within the invasive populations, suggesting a limited original introduction from a very small population followed by rapid, global range expansion in a stepwise fashion. Results of this study should provide some guidelines for characterizing invasion pathways of new invasive insect pests.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).http://link.springer.com/journal/105302019-09-01hj2019Forestry and Agricultural Biotechnology Institute (FABI)GeneticsZoology and Entomolog