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Experimental Inoculations (experimental + inoculation)
Selected AbstractsIn vitro characterization of Inocutis jamaicensis and experimental inoculation of Eucalyptus globulus standing treesFOREST PATHOLOGY, Issue 5 2009S. Lupo Summary Lesions of variable size, associated with the hymenomycete Inocutis jamaicensis, a white-rot fungus, have been observed on the stems of Eucalyptus globulus trees in Uruguay. The aim of this study was to evaluate some ecophysiological characteristics of I. jamaicensis and assess its ability to colonize E. globulus trees of two different seed origins (Geeveston and Jeeralang) and the clone, 334-1-AR, obtained by micropropagation (ENCE, Spain). The growth of an I. jamaicensis isolate (MVHC11379) was evaluated at 25°C in a medium with a water potential of 0 (, = 0). The growth rate did not vary significantly with a growth medium pH of between 4 and 7. I. jamaicensis showed no growth at either 5 or 37°C at any pH or , tested. Weight loss of heartwood and sapwood of different plant provenances inoculated with I. jamaicensis under laboratory conditions was evaluated, and significant differences observed. Lignin-modifying enzyme activity was evaluated in culture medium with or without E. globulus sawdust as substrate or inducer. Laccase activity was observed with sawdust and manganese peroxidase activity with and without sawdust. Only slight activity of aryl-alcohol oxidase and lignin peroxidase was detected without sawdust. Experimental inoculation with I. jamaicensis of 3-year-old Geeveston and Jeeralang, and of 4-year-old 334-1-AR stems, resulted in successful fungal colonization of 56% of the 334-1-AR, 50% of Geeveston and 25% of Jeeralang trees. Only the heartwood was decayed. In 334-1-AR, the rotted wood was delimited by a reaction zone. Wood characteristics and the ability of I. jamaicensis to overcome the chemical reactions in the tree could partially explain differences in susceptibility to the fungus among provenances observed under natural and laboratory conditions. [source] Do individual branches of immune defence correlate?OIKOS, Issue 2 2003A comparative case study of scavenging, non-scavenging birds Costs of immunity are widely believed to play an important role in life history evolution, but most studies of ecological immunology have considered only single aspects of immune function. It is unclear whether we should expect correlated responses in other aspects of immune function not measured, because individual branches of immune defence may differ in their running costs and thus may compete unequally for limiting resources, resulting in negatively correlated evolution. In theory such selection pressure may be most intense where species are hosts to more virulent parasites, thus facing a higher potential cost of parasitism. These issues are relatively unstudied, but could influence the efficacy of attempting to estimate the scale and cost of host investment in immune defence. Here, in a comparative study of birds we found that species that scavenge at carcasses, that were hypothesised to be hosts to virulent parasites, had larger spleens for their body size and higher blood total leukocyte concentrations (general measures of immune function) than non-scavengers. These results support the hypothesis that scavengers are subject to strong parasite-mediated selection on immune defences. However, measures of specific branches of immune function revealed that scavengers had a relatively lower proportion of lymphocytes than phagocytic types of leukocytes, suggesting robust front line immune defences that could potentially reduce the need for mounting relatively energetically costly lymphocyte-dependent immune responses. Following experimental inoculation, scavengers produced significantly larger humoral immune responses, but not cell-mediated immune responses, than non-scavengers. However, the sizes of cell-mediated and humoral immune responses were not correlated across species. These results suggest that single measures of immune defence may not characterise the overall immune strategy, or reveal the likely costs involved. [source] Activity and mode of action against fungal phytopathogens of bovine lactoferricin-derived peptidesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2006A. Muņoz Abstract Aim:, To evaluate the activity against fungal phytopathogens of two synthetic peptides derived from the protein bovine lactoferricin: the antibacterial active core of six amino acid residues (LfcinB20,25) and an extension of 15 amino acids (LfcinB17,31). Methods and Results:,In vitro activity against fungal pathogens was determined and compared with that against model micro-organisms. Activity was demonstrated against fungi of agronomic relevance. Distinct antimicrobial properties in vitro were found for the two peptides. LfcinB17,31 had growth inhibitory activity higher than LfcinB20,25. However, LfcinB17,31 was not fungicidal to quiescent conidia of Penicillium digitatum at the concentrations assayed, while LfcinB20,25 killed conidia more efficiently. Microscopical observations showed that the mycelium of P. digitatum treated with LfcinB17,31 developed alterations of growth, sporulation and chitin deposition, and permeation of hyphal cells. In experimental inoculations of mandarins, both peptides showed limited protective effect against the disease caused by P. digitatum. Conclusions:, LfcinB20,25 and LfcinB17,31 peptides were shown to have antimicrobial activity against plant pathogenic filamentous fungi, with distinct properties and mode of action. Significance and Impact of the Study:, LfcinB20,25 and LfcinB17,31 peptides offer novel alternatives to develop resistant plants by molecular breeding. [source] Maximized virulence in a sterilizing pathogen: the anther-smut fungus and its co-evolved hostsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2008D. B. SLOAN Abstract Host sterilization is a common feature of sexually transmitted diseases (STDs). Because host reproductive failure may free up resources for pathogen reproduction and transmission, theory predicts that selection on sterilizing pathogens will favour maximum virulence (i.e. complete sterilization). We examined patterns of infection in sexually transmitted anther-smut fungi (Microbotryum) on four of their host species in the Caryophyllaceae. Using controlled fungal matings and experimental inoculations, we compared disease expression in inoculations ranging from host-specific pathogens to hybrids and cross-species treatments. Our data support the existence of host-specific sibling species within the genus Microbotryum based on a low infection rate from cross-inoculations and reduced fitness for hybrid pathogens. These patterns of host specificity and reproductive isolation, however, were not absolute. We did observe some successful cross-species and hybrid infections, but the expression of disease was frequently incomplete, including only partial host sterilization and the failed dehiscence of pathogen spores. The prevalence of these maladapted disease phenotypes may greatly inhibit the emergence of novel host pathogen combinations. Infections by hybrid pathogen genotypes were intermediate, in terms of both infection rate and the normality of disease symptoms, between host-specific and cross-inoculated pathogens. In addition, the frequency with which hybrid and cross-inoculated anther-smut pathogens were able to infect but not sterilize new hosts supports the prediction that sterilizing STDs are under selection to maximize virulence in natural populations. [source] Common sex-linked deleterious alleles in a plant parasitic fungus alter infection success but show no pleiotropic advantageJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2006T. GIRAUD Abstract Microbotryum violaceum is a fungus that causes the sterilizing anther smut disease in Caryophyllaceae. Its diploid teliospores normally produce equal proportions of haploid sporidia of its two mating types. However natural populations contain high frequencies of individuals producing sporidia of only one mating type (,biased strains'). This mating type-ratio bias is caused by deleterious alleles at haploid phase (,haplo-lethals') linked to the mating type locus that can be transmitted only by intra-tetrad selfing. We used experimental inoculations to test some of the hypotheses proposed to explain the maintenance of haplo-lethals. We found a disadvantage of biased strains in infection ability and high intra-tetrad mating rates. Biased strains had no higher competitive ability nor shorter latency and their higher spore production per flower appeared insufficient to compensate their disadvantages. These findings were only consistent with the hypothesis that haplo-lethals are maintained under a metapopulation structure because of high intra-tetrad selfing rates, founder effects and selection at the population level. [source] | ||||||||||