Identification, Pathogenicity and Comparative Virulence of Fusarium spp. Associated with Diseased Euphorbia spp. in Europe

Fusarium spp. isolated from diseased Euphorbia spp. in Europe were assessed for pathogenicity to North American accessions of leafy spurge ( Euphorbia esula/virgata ). Of the nine strains of Fusarium spp. isolated from diseased E. stepposa or E. virgata in the Caucasus region of Russia and E. esula/virgata in southern France, all were pathogenic to leafy spurge. There were significant differences in virulence among strains. Four strains, including the two that were most virulent, were identified as F. oxysporum . Four of the five other strains were identified as F. solani and one was identified as F. proliferatum . Three of the four most virulent strains to leafy spurge were isolated from E. stepposa . The most virulent strain was associated with root damage caused by insect biological control agents, as found earlier with domestic strains of Fusarium spp. pathogenic to leafy spurge. Two strains identified as F. solani were vegetatively compatible. It was concluded that further screening of a larger set of strains of foreign Fusarium spp. under quarantine conditions in the US or in limited overseas facilities would be justified, and could yield promising biological control agents for leafy spurge.     

Fusarium spp. associated with rice Bakanae: ecology,genetic diversity,pathogenicity and toxigenicity

African and Asian populations of Fusarium spp. (Gibberella fujikuroi species complex) associated with Bakanae of rice (Oryzae sativa L.) were isolated from seeds and characterized with respect to ecology, phylogenetics, pathogenicity and mycotoxin production. Independent of the origin, Fusarium spp. were detected in the different rice seed samples with infection rate ranges that varied from 0.25% to 9%. Four Fusaria (F. andiyazi, F. fujikuroi, F. proliferatum and F. verticillioides) were found associated with Bakanae of rice. While three of the Fusaria were found in both African and Asian seed samples, F. fujikuroi was only detected in seed samples from Asia. Phylogenetic studies showed a broad genetic variation among the strains that were distributed into four different genetic clades. Pathogenicity tests showed that all strains reduced seed germination and possessed varying ability to cause symptoms of Bakanae on rice, some species (i.e. F. fujikuroi) being more pathogenic than others. The ability to produce fumonisins (FB₁ and FB₂) and gibberellin A3 in vitro also differed according to the Fusarium species. While fumonisins were produced by most of the strains of F. verticillioides and F. proliferatum, gibberellin A3 was only produced by F. fujikuroi. Neither fumonisin nor gibberellin was synthesized by most of the strains of F. andiyazi. These findings provide new information on the variation within the G. fujikuroi species complex associated with rice seed and Bakanae disease.     

Pathogenicity,characterization and comparative virulence of Rhizoctonia spp. from insect-galled roots of Lepidium draba in Europe

The association of Rhizoctonia spp. with insect-damaged and diseased tissue of the invasive perennial Lepidium draba was documented throughout the range of L. draba that was surveyed in Europe, including Hungary, Austria, Switzerland and France. Samples that could be both maintained under cooled conditions after collection and promptly processed consistently yielded Rhizoctonia solani, 11 isolates of which anastomosed with AG-4, one with AG-2-1 and one isolate was determined to be binucleate. Comparative virulence among the isolates was analyzed using nonparametric survival analysis for interval-censored data. This analysis indicated that there were significant differences among the isolates. These findings provide further evidence that both root-attacking insects and soilborne pathogens are associated with the lower density of a perennial invasive species in its native range. Prioritization of prospective biocontrol agents should include the ability to engage in insect/plant pathogen synergisms. The application of nonparametric maximum likelihood estimation to interval-censored data for the assessment of comparative virulence among several strains of a plant pathogen is more accessible than calculation of the area under the disease progress curve.     

Detection of virulence and pathogenicity genes in selected phytopathovars

Plant pathogenic organisms are known to infect host cell using various range of secretory proteins. Amongst all other secretion systems, type III secretion system (T3SS) is a key mechanism for bacterial pathogenesis for establishing and maintaining infection into the host. Expression levels of seven genes viz. avrXacE1, avrXacE2, hpaA and hrpG along with bacterial endogenous control lrp (leucine-responsive protein) were studied. The pathogenic organisms selected for the present study includes Enterobacter cloacae, Enterobacter spp., Pantoea ananatis, Xanthomonas campestris pv. Citri, Pantoea agglomerans, Ochrobactrum anthropi and Erwinia chrysanthemi. P. agglomerans and Enterobacter spp. gave high expression of above-mentioned virulence genes compared to Xanthomonas, while E. cloacae and P. ananatis showed similar expression with that of Xanthomonas. The detailed relationship of the expression profiles with respect to the selected organisms is discussed.     

Mycotoxins and Fusarium spp. associated with infected ears of corn in Minnesota.

Five Fusarium species were isolated from the grain of dent corn (Zea mays) selected from 20 of 32 damaged fields in 10 counties in Minnesota on the basis of hyphal growth visible on kernels in the field. Three mycotoxins were identified in the infected ears: zearalenone, deoxynivalenol, and 15-acetyl-deoxynivalenol. This is the first report of the presence of 15-acetyl-deoxynivalenol on corn ears in the field prior to harvest and in combination with deoxynivalenol and zearalenone. Ninety-nine cultures were selected from colonies growing from kernels on an agar medium; 30% of the cultures were F. graminearum, 23% were F. subglutinans, 20% were F. moniliforme, 14% were F. oxysporum, and 12% were F. proliferatum.     

Mycotoxins and Fusarium spp. associated with infected ears of corn in Minnesota

Five Fusarium species were isolated from the grain of dent corn (Zea mays) selected from 20 of 32 damaged fields in 10 counties in Minnesota on the basis of hyphal growth visible on kernels in the field. Three mycotoxins were identified in the infected ears: zearalenone, deoxynivalenol, and 15-acetyl-deoxynivalenol. This is the first report of the presence of 15-acetyl-deoxynivalenol on corn ears in the field prior to harvest and in combination with deoxynivalenol and zearalenone. Ninety-nine cultures were selected from colonies growing from kernels on an agar medium; 30% of the cultures were F. graminearum, 23% were F. subglutinans, 20% were F. moniliforme, 14% were F. oxysporum, and 12% were F. proliferatum.     

FgVELB is associated with vegetative differentiation, secondary metabolism and virulence in Fusarium graminearum

The velvet complex containing VeA, VelB and LaeA has been showed to play critical roles in the regulation of secondary metabolism and diverse cellular processes in Aspergillus spp. In this study, we identified FgVelB, a homolog of Aspergillus nidulans VelB, from Fusarium graminearum using the BLASTP program. Disruption of FgVELB gene led to several phenotypic defects, including suppression of aerial hyphae formation, reduced hyphal hydrophobicity and highly increased conidiation. The mutant showed increased resistance to osmotic stress and cell wall-damaging agents, which may be related to a high level of glycerol accumulation in the mutant. Additionally, the mutant exhibited increased sensitivity to the phenylpyrrole fungicide fludioxonil. Ultrastructural and histochemical analyses revealed that conidia of FgVELB deletion mutant contained numerous lipid droplets. Pathogenicity assays showed FgVELB deletion mutant was impaired in virulence on flowering wheat head, which is consistent with the observation that FgVelB is involved in the regulation of deoxynivalenol biosynthesis in F. graminearum. All of the defects were restored by genetic complementation of the mutant with wild-type FgVELB gene. Yeast two hybrid assays showed that FgVelB does not interact with FgVeA. Taken together, results of this study indicated that FgVelB plays a critical role in the regulation of various cellular processes in F. graminearum.     

Fungi associated with Eichhornia crassipes in South Africa and their pathogenicity under controlled conditions

Eichhornia crassipes Mart. Solms-Laubach (Pontederiaceae), water hyacinth, continues to be the world's worst aquatic weed. In South Africa, considerable research has been conducted on biological control agents associated with water hyacinth, with the release of six arthropods and one fungus, but little is known about the occurrence and impacts of native phytopathogenic fungi. Nation-wide surveys were conducted in 2010 and 2011 on various aquatic bodies of South Africa to identify the fungal pathogens associated with water hyacinth. Diseased plant parts were collected and fungi were isolated and identified. Some 250 isolates belonging to more than 25 genera were collected. Some of these represent new host records, as well as undescribed taxa. Isolates of Acremonium zonatum (Sawada) Gams, Alternaria eichhorniae Nag Raj and Ponnappa, Bipolaris hawaiiensis (M.B. Ellis) Uchida and Aragaki, Fusarium Link, Myrothecium roridum Tode ex Fr. and Ulocladium sp., showed the highest pathogenicity and have the potential to be useful in complementing the ongoing biocontrol programme on water hyacinth in South Africa.     

Fusarium spp. are Responsible for Shoot Canker of Kumquat in China

Shoot and branch canker and tree decline of kumquat (Fortunella margarita cv. Guban) were recorded in Yangshuo County, Guilin City, in the Guangxi Zhuang Autonomous Region of China during 2008–2011. Fusarium oxysporum and a new Fusarium species within the Gibberella fujikuroi complex (Fusarium sp. GLB1) were isolated repeatedly from the infected shoots and branches. Species identifications were verified by their high translation elongation factor 1‐alpha (TEF1) sequence similarity with those of the species epitypes. Koch's postulates were fulfilled on kumquat (cv. Guban) and mandarin establishing pathogenicity. To our knowledge, this is the first report of Fusarium shoot canker disease caused by F. oxysporum and Fusarium sp. on kumquat.     

Nosema meligethi I. & R. (Microsporida) in populations of meligethes spp. in Europe

Samples of rape blossom beetles, Meligethes spp., from 12 countries in Eastern and Western Europe were inspected for the occurrence of Nosema meligethi I. &R. infection. From most countries about a dozen samples and a few hundred beetles were inspected. A total of 13 910 individual beetles were checked under a compound microscope, and of these, 561 were found to be infected (4.03%). Despe careful examination, infection was not detectable in samples from the UK (1039 beetles inspected), Germany (694), Sweden (489), or Swzerland (280). One infected beetle was found among 444 beetles inspected from Austria, and one from Denmark (1/85). In contrast, the parase was found rather regularly in samples from Finland and from Eastern European countries. No obvious reason for this pattern of infection is known, but pesticide usage at or close to the sampling ses may play a role, because most samples from whichNosema was detected originated from areas where few pesticides are used. Spore size measurements were made from seven N. meligethi isolates, and they appeared relatively uniform. appears that artificial spread of the disease might be worthwhile in an effort towards the integrated control of M. aeneus F.     

Characterization of Fusarium spp. associated with pineapple fruit rot and leaf spot in Peninsular Malaysia

Pineapple (Ananas comosus) is one the important fruit crops planted in Malaysia, and this study was conducted to determine Fusarium spp. associated with diseases of the fruit crop as Fusarium is prevalent in tropical countries. Our objective was to identify and characterize Fusarium spp. associated with pineapple fruit rot and leaf spot mainly found on the fruits and leaves in Peninsular Malaysia. Fusarium isolates (n = 108) associated with pineapple fruit rot and leaf spot were characterized by morphological, molecular and phylogenetic analyses, a mating study and pathogenicity testing. TEF‐1α sequence analysis identified Fusarium proliferatum, Fusarium verticillioides, Fusarium sacchari and Fusarium sp. Mating was successful only between tester strains of F. proliferatum and F. verticillioides. Sexual crosses with standard tester strains showed that 82 isolates of F. proliferatum produced fertile crosses with mating population D (Gibberella intermedia) and three isolates of F. verticillioides were fertile with the tester strain of mating population A (Gibberella moniliformis). All isolates were pathogenic, causing pineapple fruit rot and leaf spot, thus fulfilling Koch's postulates.     

Isolation and characterization of microsatellites in Echinochloa (L.) Beauv. spp.

Five primer pairs were developed that amplify microsatellite loci in three agronomically important Echinochloa (L.) Beauv. species: E. colona (L.) Link, E. crus‐galli (L.) Beauv. and E. crus‐pavonis (Kunth) Schultes. The microsatellites were tested on 24 individuals representing three species collected in rice fields from different geographical regions and revealed 3–7 alleles per microsatellite. Gene diversity [1 ? Σp_ij²] for four polymorphic loci within E. crus‐galli ranged from 0.12 to 0.61. Alleles at a fifth locus were useful in discriminating the species. The microsatellites should provide useful markers for intraspecific diversity studies and aid classification of species within this complex genus.     

The effects of dietary additives on faecal levels of Lactobacillus spp., coliforms,and Escherichia coli,and faecal prevalence of Salmonella spp. and Campylobacter spp. in US production nursery swine1

Aims: In the United States, carbadox and copper sulfate are growth promoters commonly used in combination in nursery swine diets. Our aim was to determine how selected dietary additives affect selected bacterial populations and pathogens in nursery swine, and compare to larch extract, which contains potential antibacterial activities. Methods and Results: Piglets were weaned and sorted into one of the four treatments: (i) basal diet without antimicrobials; (ii) basal diet with carbadox + copper sulfate; (iii) basal diet + 1000 ppm larch extract; or (iv) basal diet + 2000 ppm larch extract. Diets were fed for a 4‐week period after weaning. In both trials, the carbadox + copper sulfate group consumed more feed over the 4‐week period relative to the other three diet groups (P < 0·05), but did not gain significantly more weight. Faecal shedding of Salmonella spp. was not affected by dietary supplement in either trial, but faecal shedding of Campylobacter spp. was the lowest for the carbadox + copper sulfate diet. In faecal samples collected at the end of each trial, Lactobacillus spp. cell counts for the basal and larch extract diets were nearly 1·0 log₁₀ g^?1 faeces greater (P < 0·05) than the carbadox + copper sulfate group, whereas the coliforms and Escherichia coli were nearly 1·0 log₁₀ g^?1 faeces lower (P < 0·05). Conclusions: Compared to basal fed animals, supplementation with carbadox + copper sulfate significantly altered faecal E. coli, coliform bacteria and Lactobacillus spp. Larch extract has no benefit up to 0·2% of diet in regard to pathogen shedding, whereas carbadox + copper sulfate decreased faecal shedding of Campylobacter spp. Significance and Impact of the Study: Current swine management practices in the United States may be beneficial to managing Campylobacter spp. shedding in nursery swine, but also result in significant changes in the resident gastrointestinal microflora.     

Number of triplets in 16S rRNA gene related with pathogenicity of Bacillus spp. and Clostridium spp

The relation between the number of some trinucleotides in the sequence of 16S rRNA gene and pathogenicity of bacterial species from the genera of Bacillus and Clostridium was revealed. The species of genus Bacillus, which are pathogenic for humans, mammals and insects, have an increased number of AAA and TAT triplets in 16S rRNA gene. Theoretically, these species, B. anthracis and B. cereus for example, may be detected in the specimen by the higher ratio of AAA plus TAT triplets to the number of GGG triplet. Species of genus Clostridium, which are pathogenic for humans and mammals, have a maximum ratio of AAA and TAT triplet numbers. This ratio was higher than 2.6 for pathogenic species and lower than 2.2 for saprophytic ones. These theoretical data may open a new way for detecting pathogenic bacteria through the determination of triplet numbers in the sequences of 16S rRNA or rRNA. However, the mechanism of evolutionary relation between the number of AAA and TAT triplets in the sequence of 16S rRNA gene and the pathogenicity of bacterial species is not known.     

Identification of gene clusters associated with fusaric acid, fusarin, and perithecial pigment production in Fusarium verticillioides

The genus Fusarium is of concern to agricultural production and food/feed safety because of its ability to cause crop disease and to produce mycotoxins. Understanding the genetic basis for production of mycotoxins and other secondary metabolites (SMs) has the potential to limit crop disease and mycotoxin contamination. In fungi, SM biosynthetic genes are typically located adjacent to one another in clusters of co-expressed genes. Such clusters typically include a core gene, responsible for synthesis of an initial chemical, and several genes responsible for chemical modifications, transport, and/or regulation. Fusarium verticillioides is one of the most common pathogens of maize and produces a variety of SMs of concern. Here, we employed whole genome expression analysis and utilized existing knowledge of polyketide synthase (PKS) genes, a common cluster core gene, to identify three novel clusters of co-expressed genes in F. verticillioides. Functional analysis of the PKS genes linked the clusters to production of three known Fusarium SMs, a violet pigment in sexual fruiting bodies (perithecia) and the mycotoxins fusarin C and fusaric acid. The results indicate that microarray analysis of RNA derived from culture conditions that induce differential gene expression can be an effective tool for identifying SM biosynthetic gene clusters.