First report of bacterial wilt caused by Ralstonia solanacearum on eucalypts in South Africa

Ralstonia solanacearum, the causal agent of bacterial wilt, has one of the widest host ranges of all phytopathogenic bacteria. This pathogen was first reported on Eucalyptus spp. in the late 1980s in Brazil. Since then, there have been reports of its occurrence on this host in Australia, China and Venezuela. Early in 1997, an 18‐month‐old clonally propagated Eucalyptus grandis × Eucalyptus camaldulensis (GC) hybrid in Zululand, KwaZulu/Natal, showed signs of wilting. The vascular tissue of infected trees was dicoloured and bacterial exudation was produced from cut surfaces. The bacterium was consistently isolated from diseased tissue, purified and identified as R. solanacearum biovar 3 race 1, using the BioLog bacterial identification system. Inoculation trials were conducted on three E. grandis × E. camaldulensis clones (GC515, GC550 and GC505). Clone GC550 displayed wilting after 3 days and all cuttings subsequently died. Clones GC515 and GC505 appeared to be less susceptible with cuttings not showing signs of disease until 7 days after inoculation. After 14 days, 90 and 80%, respectively, of cuttings of these two clones had died. This is the first report of bacterial wilt on Eucalyptus in South Africa.     

Evaluation of cardiorespiratory and biochemical effects of ketamine‐propofol and guaifenesin‐ketamine‐xylazine anesthesia in donkeys (Equus asinus)

ObjectivesTo evaluate the cardiorespiratory and biochemical effects of ketamine-propofol (KP) or guaifenesin-ketamine-xylazine (GKX) anesthesia in donkeys.Study designProspective crossover trial.AnimalsEight healthy, standard donkeys, aged 10 ± 5 years and weighing 153 ± 23 kg.MethodsDonkeys were premedicated with 1.0 mg kg^?1 of xylazine (IV) in both treatments. Eight donkeys were administered ketamine (1.5 mg kg^?1) and propofol (0.5 mg kg^?1) for induction, and anesthesia was maintained by constant rate infusion (CRI) of ketamine (0.05 mg kg^?1 minute^?1) and propofol (0.15 mg kg^?1 minute^?1) in the KP treatment. After 10 days, diazepam (0.05 mg kg^?1) and ketamine (2.2 mg kg^?1) were administered for induction, and anesthesia was maintained by a CRI (2.0 mL kg^?1 hour^?1) of ketamine (2.0 mg mL^?1), xylazine (0.5 mg mL^?1) and guaifenesin (50 mg mL^?1) solution. Quality of anesthesia was assessed along with cardiorespiratory and biochemical measurements.ResultsAnesthetic induction took longer in GKX than in KP. The induction was considered good in 7/8 with KP and in 6/8 in GKX. Anesthetic recovery was classified as good in 7/8 animals in both treatments. Xylazine administration decreased heart rate (HR) in both treatments, but in KP the HR increased and was higher than GKX throughout the anesthetic period. Respiratory rate was higher in GKX than in KP. PaO₂ decreased significantly in both groups during the anesthetic period. Glucose concentrations [GLU] increased and rectal temperature and PCV decreased in both treatments. Arterial lactate [LAC] increased at recovery compared with all time points in KP. [GLU] and calcium were higher in GKX than in KP at recovery.Conclusion and clinical relevanceThese protocols induced significant hypoxemia but no other cardiorespiratory or metabolic changes. These protocols could be used to maintain anesthesia in donkeys, however, they were not tested in animals undergoing surgery.     

Sources of resistance in Musa to Xanthomonas campestris pv. musacearum,the causal agent of banana xanthomonas wilt

It is claimed that, with the exception of Musa balbisiana, all banana varieties are susceptible to bacterial wilt caused by Xanthomonas campestris pv. musacearum (Xcm). Despite being resistant to Xcm infection, M. balbisiana is not preferred for breeding because it belongs to the BB genome subgroup, while most edible bananas are of the A genome. To identify potential sources of resistance to Xcm, 72 banana accessions representing the Musa genetic diversity were evaluated in an outdoor confined potted trial. The midribs of the youngest leaf of 3-month-old banana plants were inoculated with 10⁸ CFU mL⁻¹ of Xcm isolate USY13P, and symptom development assessed weekly for 4 months. Results confirmed that M. balbisiana genotypes are indeed resistant to Xcm. Varieties within the Musa acuminata subsp. zebrina (AA) set were further identified as potentially useful sources of Xcm resistance. These findings reveal the potential to develop banana and plantain varieties with tolerance to Xcm.     

植物油对谷象诱虫性的估价

在装有1公斤小麦的圆盘内,用培养皿测试某些植物油对谷象Sitophilus granarius L.的诱虫性或驱虫性。与矿物油比较,冷榨未提炼的燕麦油,能量油(混合油)麦芽油,芥籽油,有强的诱虫性(P<0.05),而提炼后的燕麦油有强的驱虫性;新鲜的麦芽油和能量油的诱性优于各自陈化的油。向日葵油分别与麦芽油,南瓜籽油,红花油等量混合,其诱性降低,而与提炼的燕麦油、芝麻油、或棉籽油与芝麻油,提炼燕麦油等混合,其驱虫性将增加。     

The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.     

Wood ash effects on nutrient dynamics and soil properties under Mediterranean climate

Aims

This study aims to evaluate the effects of wood ash application on nutrient dynamics and soil properties of an acidic forest soil (Arenosol).

Methods

Treatments were loose and pelleted ash application (11?Mg?ha^?1), alone or together with N fertiliser, and control treatment in a lysimeter experiment. Nutrient leaching was followed during a 2-year period and soil chemical and biological properties were evaluated at the end of the experiment.

Results

Wood ash increased leaching of total N, NH ₄ ⁺ -N, base cations and P, mainly during the first months, the effect being more pronounced for the loose formulation. At the end of the study period, a positive effect on soil nutrient availability and soil acidity reduction was seen. The application of loose and pelleted ash alone decreased N leaching and increased N microbial biomass at the end of the experiment. The C dynamics was weakly affected.

Conclusion

Wood ash can be used to improve nutrient availability and balance nutrient exported by tree harvesting in acid forest soils, the effects at short-term being stronger for loose than for pelleted ash. However, their application should be carried out when vegetation is established to minimise nutrient losses at short-term and reduce the potential risk for water bodies. In N-limited soils, wood ash should be applied with N fertilisers to counteract N immobilisation.     

Synergistic antibiotic activity of volatile compounds from the essential oil of Lippia sidoides and thymol

Lippia sidoides Cham. (Verbenaceae) is used in the folk medicine as topical antiseptic in skin and mucous membranes and its therapeutic effect is attributed to the thymol presence. The objective of this work was to verify the chemical composition and antibiotic modifying activity of the essential oil extracted from the leaves of L. sidoides and its major component thymol. The essential oil was obtained by hydrodistillation and analyzed by GC/MS. The synergistic activity was evaluated using gaseous contact method. The essential oil was obtained (yield of 1.06%) and the GC/MS analysis identified the main constituents: thymol (84.9%) and p-cymene (5.33%). The antibiotic modifying activity was verified using the minimal inhibitory dose method and gaseous contact. It verified the interference of essential oil and thymol against all tested aminoglycosides. There were no statistical differences between the activity of the essential oil and thymol against Pseudomonas aeruginosa, indicating this to be the responsible composition for such activity. However, the oil was shown more effective when compared to the thymol against Staphylococcus aureus. The essential oil of L. sidoides and its major component thymol influence the activity of aminoglycosides and may be used as adjuvant in antibiotic therapy against respiratory tract bacterial pathogens.     

Carbon‐mineralization kinetics in an organically managed Cambic Arenosol amended with organic fertilizers

The dynamics of C mineralization in an organically managed Cambic Arenosol amended with hen manure, a stabilized compost (compost), and three different combinations of both fertilizers (varying from a 1:100 to a 1:10 ratio) were studied during an incubation experiment to estimate the potential of such combinations to preserve/restore soil C content relative to single applications. A strong increase of the CO₂‐C emissions relative to the unamended soil (control) was observed after soil application of all five organic‐fertilizer treatments. A significantly higher amount of applied C was lost in hen‐manure treatment (648 mg CO₂‐C [g C applied]^–1) when compared to compost (159 mg CO₂‐C [g C applied]^–1) or to the three combined treatments (176–195 mg CO₂‐C [g C applied]^–1). The first‐order exponential model and the double exponential model were used to fit the C‐mineralization data in the treatments considered. Results showed that mixing “small” amounts of hen manure with compost did not affect the total amount of potentially mineralizable C, but significantly increased the mineralization rate constant. Clearly, combinations of both fertilizers promoted an initial faster mineralization of the organic matter, and consequently a faster release of nutrients, without affecting the total amount of C sequestered in soil.     

Molecular characterization of Endothia gyrosa isolates from Eucalyptus in South Africa and Australia

Endothia gyrosa is a canker pathogen best known as the causal agent of pin oak blight in North America, and causes cankers on other woody hosts such as Castanea spp. and Liquidambar spp. In South Africa, Australia and Tasmania, a fungus identified as E. gyrosa has been recorded on Eucalyptus spp. Some morphological differences exist between the North American fungus and the isolates from Eucalyptus . Phylogenetic relationships between E. gyrosa from North America and E. gyrosa from South Africa and Australia, as well as that of the related fungi Cryphonectria parasitica and C. cubensis , were studied using PCR-based restriction fragment length polymorphism (RFLP) and sequences of the internal transcribed spacer (ITS) region of the rRNA operon. Endothia gyrosa isolates from South Africa produced the same RFLP banding patterns as those from Australia, which differed markedly from North American isolates of E. gyrosa . In a phylogram based on the DNA sequences, the Australian and South African isolates of E. gyrosa resided in a single, well resolved clade, distinct from North American isolates. Isolates of C. parasitica grouped in the same clade as the South African and Australian isolates of E. gyrosa , but C. cubensis was distantly related to them. The molecular data suggest that the E. gyrosa isolates from South Africa and Australia represent a distinct taxon, and probably belong to the genus Cryphonectria .