16 research outputs found

    Nematicidal activity of Paecilomyces marquandii proteases on infective larvae of Ancylostoma spp

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    ABSTRACT The present study aimed to evaluate the action of Paecilomyces marquandii proteases on Ancylostoma spp L3. White halos in the zymogram confirmed the proteolytic action. Difference (p <0.01) between the number of L3 in the differents groups was found, with 41.4% of reduction of Ancylostoma spp. L3 before 24 hours

    The Plant Pathogen Phytophthora andina Emerged via Hybridization of an Unknown Phytophthora Species and the Irish Potato Famine Pathogen, P. infestans

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    Emerging plant pathogens have largely been a consequence of the movement of pathogens to new geographic regions. Another documented mechanism for the emergence of plant pathogens is hybridization between individuals of different species or subspecies, which may allow rapid evolution and adaptation to new hosts or environments. Hybrid plant pathogens have traditionally been difficult to detect or confirm, but the increasing ease of cloning and sequencing PCR products now makes the identification of species that consistently have genes or alleles with phylogenetically divergent origins relatively straightforward. We investigated the genetic origin of Phytophthora andina, an increasingly common pathogen of Andean crops Solanum betaceum, S. muricatum, S. quitoense, and several wild Solanum spp. It has been hypothesized that P. andina is a hybrid between the potato late blight pathogen P. infestans and another Phytophthora species. We tested this hypothesis by cloning four nuclear loci to obtain haplotypes and using these loci to infer the phylogenetic relationships of P. andina to P. infestans and other related species. Sequencing of cloned PCR products in every case revealed two distinct haplotypes for each locus in P. andina, such that each isolate had one allele derived from a P. infestans parent and a second divergent allele derived from an unknown species that is closely related but distinct from P. infestans, P. mirabilis, and P. ipomoeae. To the best of our knowledge, the unknown parent has not yet been collected. We also observed sequence polymorphism among P. andina isolates at three of the four loci, many of which segregate between previously described P. andina clonal lineages. These results provide strong support that P. andina emerged via hybridization between P. infestans and another unknown Phytophthora species also belonging to Phytophthora clade 1c

    Species Tree Estimation for the Late Blight Pathogen, Phytophthora infestans, and Close Relatives

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    To better understand the evolutionary history of a group of organisms, an accurate estimate of the species phylogeny must be known. Traditionally, gene trees have served as a proxy for the species tree, although it was acknowledged early on that these trees represented different evolutionary processes. Discordances among gene trees and between the gene trees and the species tree are also expected in closely related species that have rapidly diverged, due to processes such as the incomplete sorting of ancestral polymorphisms. Recently, methods have been developed for the explicit estimation of species trees, using information from multilocus gene trees while accommodating heterogeneity among them. Here we have used three distinct approaches to estimate the species tree for five Phytophthora pathogens, including P. infestans, the causal agent of late blight disease in potato and tomato. Our concatenation-based “supergene” approach was unable to resolve relationships even with data from both the nuclear and mitochondrial genomes, and from multiple isolates per species. Our multispecies coalescent approach using both Bayesian and maximum likelihood methods was able to estimate a moderately supported species tree showing a close relationship among P. infestans, P. andina, and P. ipomoeae. The topology of the species tree was also identical to the dominant phylogenetic history estimated in our third approach, Bayesian concordance analysis. Our results support previous suggestions that P. andina is a hybrid species, with P. infestans representing one parental lineage. The other parental lineage is not known, but represents an independent evolutionary lineage more closely related to P. ipomoeae. While all five species likely originated in the New World, further study is needed to determine when and under what conditions this hybridization event may have occurred

    Molecular diagnostics in plant health

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    In several crops, their quality and condition is very important. The products are relatively expensive and plant diseases can destroy valuable harvests in a very short time. The presence or absence of plant pathogens and pests, therefore, needs to be accurately tested. For decades, identification and detection methods have been designed to demonstrate that starting material for further propagation and also certified bulbs, tubers, cuttings, and plants are free of many plant pathogens. Every year, millions of plants are tested, including approximately one and a half million bulbs. Despite the ease of low-cost, fast, and well-automated test methods, such as ELISA, more and more molecular-based techniques are used the last decade. These techniques are, generally, more specific and more sensitive. These new tests are also necessary because plant pathogens are often latent (asymptomatic) present in the material to be tested. The Netherlands has a high in—and export of plants and plant products. These large trading volumes may harbour many plant pathogens. The European Commission has drawn up a list of unwanted plant pathogens (quarantine organisms). This list contains more than 300 different organisms (viruses, bacteria, fungi, phytoplasmas, nematodes and insects). Each EU-country has to control the in—and export traffic of plants and plant products for the introduction of these unwanted organisms. In the Netherlands, this task is performed by four inspection services: Naktuinbouw (Netherlands Inspection Service for Horticulture), NAK (The Dutch General Inspection Service), BKD (Inspection Service for Flowerbulbs) and KCB (Quality Control Bureau). The NVWA (Dutch Food and Consumers Authority) is the NPPO (National plant protection organisation) in the Netherlands and supervises the inspection services. Many different molecular methods are used daily for the detection and identification of many plant pathogens and plant diseases
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