Invasive potential of biofilm-forming Staphylococci bovine subclinical mastitis isolates

Staphylococcus (S.) aureus is a common infectious agent of bovine chronic mastitis, a disease that is difficult to eradicate. The abilities of Staphylococci to be internalized and form a biofilm can contribute to host immunological defence evasion that subsequently impairs antimicrobial therapy. The invasive capability of six S. aureus field isolates with different biofilm-forming profiles was compared in vitro using a bovine mammary epithelial cell line. This was further confirmed in primary cell cultures using fluorescent rRNA probes against S. aureus. The results suggest that S. aureus invasion levels are not related to biofilm formation.     

Aneuploid hybrids from 5x − 4x crosses in potato: Chromosome number, fertility, morphology and yield

The objective of this study was to characterize sixS. commersonii - S. tuberosum progenies deriving from 5x ? 4x crosses to provide evidence that they can be used in potato breeding. Hybrids analyzed (coded PTH) had a chromosome number between the 4x and the 5x level. In particular, progeny means for chromosome number ranged from 50±0.5 to 54±0.7, with most (70%) genotypes exhibiting a low aneuploid level of 48 to 53 chromosomes. Despite being aneuploid, the hybrids did not generally show phenotypic aberrations or vigor reduction common to aneuploids of other species. Most genotypes resembledS. tuberosum in growth habit, whereas corolla type, eye depth, and stolon length varied between and within progenies. Aneuploid hybrids produced tubers under long-day conditions. However, tuber yields were not as high as expected, probably due to lack of adaptation of theS. commersonii genome to long-day conditions. Although aneuploidy has often been associated with reduced male and female fertility, many 5x ? 4x hybrids were fertile in crosses withS. tuberosum. The average berry set and number of seeds/berry were 33% and 34.7, respectively, following PTH ×S. tuberosum crosses, and 40% and 51.7, respectively, forS. tuberosum × PTH crosses. The useful variation for fertility and tuber traits found in this material is being used for further breeding efforts.     

The native South American crayfishes (Crustacea,Parastacidae): state of knowledge and conservation status

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Water Remediation by Adsorption of Phenol onto Hydrophobic Modified Clay

In this work we studied the phenol sorption from contaminated water onto modified clay mineral vermiculite and bentonite by insertion of hexadecyltrimethylammonium in the interlayer of clays. The non modified clays showed negligible interaction with phenol. The experimental data were treated using the Freunlich equation which had a good fit. The removal percentages were higher than 35% for modified vermiculite and for modified bentonite, 30%. Vermiculite and bentonite were compared for the removal of phenol from an aqueous solution based on the maximum adsorption capacity of each adsorbent, and no significant difference was found. The adsorption mechanism for both is the same, according to the results. Although, there is a lack of studies using vermiculite for this purpose, it can be concluded that hydrophobic modified vermiculite is very effective for removing phenol from water. Hydrophobic modified bentonite also remove phenol, but in lower proportions.     

Alternatives to regular urea for abating N losses in lettuce production under sub-tropical climate

Alternative fertilization practices are needed for reducing gaseous and leaching N losses at high urea application rates. The objective of this study was to compare gaseous N emissions (N₂O and NH₃) and NO₃ ^? concentrations in the soil solution during two successive lettuce cropping seasons under contrasting fertilization practices. Treatments were fertilization with regular urea (U), urea treated with urease [N-(n-butyl) thiophosphoric triamide (NBPT)] and nitrification [dicyandiamide (DCD)] inhibitors (UIs), non-acidified pig slurry compost (PSC), acidified pig slurry compost (APSC), and an unfertilized control (C). Acidification of pig slurry during composting had no impact on soil cumulative N₂O emissions during the cropping seasons. The use of composts resulted in emission factors (EFs) (PSC, 0.09% of applied N; APSC, 0.16%) an order of magnitude smaller than with regular urea (1.63%). Similarly, adding NBPT and DCD to urea reduced the N₂O EF from 1.63 to 0.37% of applied N and fertilizer-induced NH₃ emissions from 30.2 to 3.4% of applied N. Composts and UI resulted in yield-scaled N₂O emissions that were 33 to 49% lower than the unfertilized control and 64 to 73% lower than the regular urea estimates, indicating a greater efficiency of supplied N with composts and UI. Nitrate concentration of the soil solution (at 0.1 and 0.3 m) in PSC, APSC, and UI plots was similar to the control and up to 17 times lower than with regular urea, indicating reduced risks for leaching losses. We conclude that, as compared to regular urea, the use of composted pig slurry, with and without acidification, and the addition of NBPT and DCD inhibitors to urea are good practices to reduce environmental N losses from lettuce production under sub-tropical climate.     

Relationships Between Internal Brown Spot and Skin Roughness in Potato Tubers Under Field Conditions

Internal brown spot (IBS) is a physiological disorder of potato tubers consisting in the appearance of punctiform and/or enlarged rust-coloured necrosis in parenchymal tissues. The IBS disorder leads to important economic impact and yield depreciation since quality, sensory and processing features of tubers may be highly compromised. Nowadays, the causes of IBS are still debated; however, the combination of several genetic, nutritional and environmental factors seems to have a relevant role in modulation of symptoms. In the current work, IBS occurrences together with skin roughness were monitored in potato tubers of different cultivars harvested in 2 years of field trials under different field conditions (environment, irrigation rate). All three IBS-susceptible cultivars used, Luminella, Majestic and Ricciona di Napoli, showed significant IBS incidence. Importantly, incidence and severity increased with tuber size. Ricciona di Napoli was the cultivar most affected by both IBS and skin roughness. Findings showed a strong positive correlation between IBS and skin roughness, suggesting that suboptimal growth conditions may have affected both physiological disorders. The association between IBS and potato skin roughness may provide new insights for the implementation of non-destructive IBS detection in potatoes.     

Sensitivity of mitochondrial respiration to different inhibitors in Venturia inaequalis

The sensitivity of Venturia inaequalis field isolates to inhibitors of the cytochrome bc1 complex at the Qo site (QoIs) was characterised at the molecular, biochemical and physiological level, and compared to other respiration inhibitors. Comparison of a sensitive and a QoI-resistant isolate revealed very high resistance factors both in mycelium growth and spore germination assays. Cross-resistance was observed among QoIs such as trifloxystrobin, azoxystrobin, famoxadone, strobilurin B and myxothiazol. In the mycelium growth assay, antimycin A, an inhibitor of the cytochrome bc1 complex at the Qi site, was less active against the QoI-resistant than against the sensitive isolate. The mixture of QoIs with salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase, exerted synergistic effects in the spore germination but not in the mycelium growth assay. Thus, the cytochrome and the alternative respiration pathways are assumed to play different roles, depending on the developmental stage of the fungus. Induction of alternative oxidase (AOX) by trifloxystrobin was observed in mycelium cells at the molecular level for the sensitive but not the resistant isolate. Following QoI treatment, respiration parameters such as oxygen consumption, ATP level, membrane potential and succinate dehydrogenase activity were only slightly reduced in Qo-resistant mycelium cells, and remained at much higher levels than in sensitive cells. In contrast, no difference was observed between sensitive and resistant isolates when NADH consumption was measured. Comparison of the cytochrome b (cyt b) gene of the sensitive and resistant isolates did not reveal any point mutations as is known to occur in resistant isolates of other plant pathogens. It is assumed that QoI resistance in V inaequalis may be based on a compensation of the energy deficiency following QoI application upstream of the NADH dehydrogenase of the respiratory chain.     

Detection of Mycobacterium avium subsp. paratuberculosis in bovine fecal samples: comparison of three polymerase chain reaction-based diagnostic tests with a conventional culture method.

Three commercially available assays, designed to specifically detect the presence of Mycobacterium avium subsp. paratuberculosis (MAP) in fecal samples by IS900-PCR, were compared with a conventional culture method. Fecal samples from 100 dairy cows were tested. Fifty-four (67.5%) of 80 culture-positive samples were positive for an assay that detects MAP DNA by dot spot hybridization of polymerase chain reaction products (kit A), 48 (60%) were positive by an assay using ethidium bromide staining for agar gel visualization of amplification products (kit B), and 49 (61.3%) were positive by an assay in which amplified products are detected by a colorimetric detection system (kit C). Relative sensitivity of all tests increased in proportion to the presence of MAP in fecal samples. Specificity was 100% based on results from 20 culture-negative samples from an MAP-free herd.     

Genetics of Host-Pathogen Relationships Between Venturia inaequalis Races 6 and 7 and Malus Species

ABSTRACT Resistance to scab originating from Malus floribunda clone 821 is the most widely form of resistance used in apple breeding programs. A dominant gene, named Vf, was introgressed from this clone into recent cultivars, although the genetic determinants of the resistance of M. floribunda 821 are apparently more complex than a single gene. The appearance of new races overcoming the resistance of cultivars with the Vf gene, the parental clone, or both made it possible to undertake a genetic analysis of host-pathogen interactions. The segregation of resistance in progenies of crosses from 'Golden Delicious' x M. floribunda 821 and 'Golden Delicious' x 'Idared' into five strains of Venturia inaequalis-races 1 (strains 104, 1093, and 301), 6 (strain 302), and 7 (strain 1066)-demonstrated the existence of a second dominant gene in M. floribunda 821. This gene, independent of Vf, was named Vfh because it seemed to induce a hypersensitive reaction. The results obtained with strain 1066, virulent to M. floribunda 821, allowed identification of another dominant gene, Vg, responsible for the resistance of 'Golden Delicious' to this strain. Vg is also carried by 'Florina', which was selected for its Vf resistance. The pathogenicity of a progeny originating from a cross between V. inaequalis strains 1066 and 301, characterized in vitro on leaf disks of differential genotypes, revealed two independent avirulence genes involved in the pathogenicity toward the Vg and Vf genes, respectively. These avirulence genes were named Avr Vg and Avr Vf. The host-pathogen interactions detected are consistent with a gene-for-gene relationship.