The influence of time,soil moisture and exogenous factors on the survival potential of oospores and chlamydospores of Phytophthora cinnamomi

The mode of persistence of Phytophthora cinnamomi, a highly aggressive soil‐ and water‐borne pathogen, remains unclear. This study investigated the survival of viable oospores and chlamydospores of P. cinnamomi when present as free propagules in untreated soil, or in soil subject to four exogenous treatments: smoke water, fish emulsion and two fungicides (ridomil and furalaxyl). The exogenous treatments were applied under moist and dry soil conditions. Spore viability was determined by the thiazolyl blue tetrazolium bromide (MTT) staining technique, with a qPCR assay used to compare general patterns of decline. Over 96% of oospores lost viability over a period of 48 weeks irrespective of soil moisture conditions. The mean percentage viability for oospores decreased from 91% at time zero to 72, 35, 20 and 1% after 6, 12, 24 and 48 weeks, respectively. Reduction in viability of chlamydospores was more rapid than oospores, with viability declining from 92% to zero after 12 weeks. There was no significant difference between untreated soil and the exogenous treatments. The RNA‐based qPCR assay indicated a strong presence of viable oospores of P. cinnamomi up to week 12 for moist soil and week 3 for dry soil, but thereafter failed to detect RNA even though viable oospores could be detected by MTT staining. Based on the MTT staining, this study indicated that viability of P. cinnamomi oospores may be entirely lost within 1 year and that of chlamydospores within 3 months for the soil type tested. Therefore, oospores and chlamydospores when existing as free propagules in soil appear unlikely to be involved in the long‐term survival of P. cinnamomi.     

Medicago truncatula DMI1 required for bacterial and fungal symbioses in legumes

Legumes form symbiotic associations with both mycorrhizal fungi and nitrogen-fixing soil bacteria called rhizobia. Several of the plant genes required for transduction of rhizobial signals, the Nod factors, are also necessary for mycorrhizal symbiosis. Here, we describe the cloning and characterization of one such gene from the legume Medicago truncatula. The DMI1 (does not make infections) gene encodes a novel protein with low global similarity to a ligand-gated cation channel domain of archaea. The protein is highly conserved in angiosperms and ancestral to land plants. We suggest that DMI1 represents an ancient plant-specific innovation, potentially enabling mycorrhizal associations.     

Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

Purpose

Wildfires represent one of the major natural disturbances within forested landscapes and have potential implications for the quality and function of downstream aquatic ecosystems. This study aimed to determine if a wildfire in a mountainous, forested watershed in British Columbia, Canada, caused a change in the dominant sediment source in the immediate 1?C2?years following the wildfire, and if the sediment sources changed over the medium term (3?C7?years) as the landscape recovered.

Materials and methods

Source materials (surface soil, subsurface soil and channel bank material) and fluvial (suspended and channel bed) sediment samples were collected over the period 2004 to 2010 from a watershed burnt by a wildfire in 2003, and from an adjacent watershed that was not impacted by the fire. Samples were analysed for the fallout radionuclides (FRNs) caesium-137 (¹³⁷Cs) and unsupported lead-210 (²¹⁰Pb_un). An unmixing model was used to calculate the relative source contributions of the fluvial sediment samples.

Results and discussion

¹³⁷Cs and ²¹⁰Pb_un were concentrated in the upper layers of surface soils in both watersheds and were statistically different to concentrations in subsurface and channel bank material. In the burnt watershed, FRN concentrations were greatest in the ash layer. Sediment sources as determined by the unmixing model were 100?% subsurface/channel bank material in the unburnt watershed, while in the burnt watershed 8.5?±?2.5?% was derived from surface soils. In both watersheds, there were no major changes in the relative contributions from surface soil and from subsurface/channel bank material over the period 2004 to 2010. Thus, while the wildfire did cause a change in sediment sources, it was fairly subtle and did not conform to the effects following wildfire described for other studies in contrasting environments, which typically document a major increase in hillslope contributions relative to channel bank sources.

Conclusions

There was a limited response in terms of fine-grained sediment sources (and also sediment fluxes) in the burnt watershed. The reason for this muted response to a severe wildfire is likely to be the lack of precipitation, especially winter precipitation and the associated snowmelt, in the first year following the wildfire. Thus while the landscape was primed for erosion and sediment transport, the lack of a driving force meant that there was a limited immediate post-fire sediment response.     

Responses of bottlenose dolphins (Tursiops spp.) to small drones

1. Recent advances in aerial drones offer new insights into the biology, ecology and behaviour of marine wildlife found on or near the ocean’s surface. While opening up new opportunities for enhanced wildlife monitoring, the impacts of drone sampling and how it might influence interpretations of animal behaviour are only just beginning to be understood.
2. The capacity of drones to record bottlenose dolphin (Tursiops spp.) behaviour was investigated, along with how the presence of a small drone at varying altitudes influences dolphin behaviour. Over 3 years and eight locations, 361 drone flights were completed between altitudes of 5 and 60 m above the ocean.
3. Analyses showed that dolphins were increasingly likely to change behaviour with decreasing drone altitude. A positive correlation was also found between time spent hovering above a group of dolphins and the probability of recording a behavioural response. Dolphin group size also influenced the frequency of an observed behavioural change, displaying a positive correlation between behaviour change and group size.
4. Overall, although drones have the potential to impact coastal dolphins when flown at low altitudes, they represent a useful tool for collecting ecological information on coastal dolphins owing to their convenience, low cost and capacity to observe behaviours underwater. To maximize benefits and minimize impacts, this study suggests that drones should be flown 30 m above coastal bottlenose dolphins.

     

Harvesting alternatives for mallee agroforestry plantations in Western Australia

The authors tested two harvesting systems especially designed for mallee agroforestry plantations on farmland. Both systems were based on versatile forest technology commonly used for conventional logging operations. They differed especially for the felling technology: small-scale drive-to-tree or industrial swing-to-tree equipment. Both systems were tested side-to-side on 12 experimental plots each. The resulting harvesting cost was 22 and 27 AU$ t^?1, for the industrial and the small scale system, respectively. Chipping represented between 60 and 80 % of the overall harvesting cost, and offered much room for improvement. The industrial system always offered the lowest harvesting cost, regardless of annual usage, when equipment mobilisation costs were not considered. The productivity of conventional forestry equipment was strongly dependent on belt stocking and tree size. If the diameter at ankle height dropped below 10 cm, economic viability decreased very rapidly.     

Facial swelling and discharging lesions associated with abnormalities of the mandible in kunekune pigs

Abstract

CASE HISTORIES: Four adult kunekune pigs developed facial swelling at the base of the right ear that ruptured and discharged food material. A further six pigs that had similar clinical signs were reported by members of the New Zealand Kunekune Association who responded to an email survey, one of which was confirmed by post-mortem examination.

CLINICAL FINDINGS: Inside the mouth of each pig there was an opening at the junction of the body and ramus of the mandible just lateral to the most caudal visible molar that was impacted with masticated feed. The food packed into the mandible resulted in infection and progressive erosion of the medullary cavity of the bone until it reached the ramus where it eroded through the lateral cortex. The feed material then tracked through the soft tissues to form a subcutaneous abscess, which eventually ruptured resulting in a draining lesion. In Case 2, which had had the lesion for 2 years, the cavity in the mandible was lined with mucosa that had healed to the skin to produce a fistula. In all four pigs there was also a lesion in the left side of the mandible that was not as developed as that on the right side.

DIAGNOSIS: The facial swellings were produced by feed material that had impacted into the mandible through an opening immediately caudal to the cheek teeth and then emerged through one or more lesions in the lateral aspect of the ramus of the mandible.

CLINICAL RELEVANCE: Although it has not been previously reported, anecdotal reports and our survey suggest that this condition may occur relatively frequently in kunekune pigs. It should be considered as a differential diagnosis for facial swellings and discharging lesions in these animals.     

Osseous lesions resembling vaccine-site sar comas in two cats

Extract

Lytic lesions with microscopic features similar to those of vaccine-site sarcomas were diagnosed in the distal femur of two young neutered male cats, one a 20-month-old Birman and the other an 18-month-old domestic short-hair (DSH). Radiographically, there was extensive destruction of trabecular and cortical bone in the metaphysis and/or epiphysis of the distal femur. The DSH cat also had angular deformity of the distal femur due to asymmetrical involvement of the physis. Histologically, the lesions in both cats consisted of dense, interwoven bundles of fibrous connective tissue, amongst which there were variable numbers of plump malignant mesenchymal cells, often with very large, hyperchromatic nuclei and irregularly shaped nucleoli. Several focal aggregates of small lymphocytes were present in both tumours. Although neither cat had apparently been vaccinated in the hindlimb it is possible that the tumours had been triggered by injection of some other irritant material.     

Effects of initial and extended exposure to an endophyte-infected tall fescue seed diet on faecal and urinary excretion of ergovaline and lysergic acid in mature geldings

Abstract

AIM: To determine the amount of ergovaline and lysergic acid retained or excreted by geldings fed endophyte-infected seed containing known concentrations of these alkaloids, and the effects of exposure time on clinical expression of toxicosis.

METHODS: Mature geldings (n=10) received diets containing either endophyte-free (E-) or endophyte-infected (E+) tall fescue seed during three experimental phases. The first phase (Days ?14 to ?1) was an adaptation phase, to allow all horses to adapt to a diet containing E- tall fescue seed. The second (Days 0 to 3) was the initial exposure phase to E+ tall fescue seed, used for the delivery of ergovaline and lysergic acid at 0.5 and 0.3 mg/kg of diet, respectively, to test the initial effects of exposure on routes and amounts of elimination of alkaloid. During this phase, half the geldings were exposed to an E+ diet while the rest served as controls by remaining on the E- diet. Once assigned to treatments, geldings remained on the same diet through the third phase (Days 4 to 21), which served as the extended exposure phase. Total outputs of faeces and urine were collected within each phase, to determine retention of ergovaline and lysergic acid and nutrient digestibility. Serum was collected weekly and analysed for activities of enzymes and concentrations of prolactin. Bodyweights (BW) and rectal temperatures were recorded weekly.

RESULTS: BW, rectal temperature, enzyme activities and concentrations of prolactin in serum, and nutrient digestibility were not affected by treatment. Total intake of ergovaline by geldings on the E+ diet was 3.5 and 3.6 (SE 0.20) mg/day, and 2.1 and 2.3 (SE 0.11) mg/day were not accounted for in initial and extended phases, respectively. Lysergic acid was excreted in the urine (4.0 and 4.9 (SE 0.97) mg/day) and faeces (2.5 and 2.7 (SE 0.35) mg/day) at greater amounts than that consumed (2.0 and 1.9 (SE 0.09) mg/day) during the initial and extended exposure phases, respectively. Animals exposed to E+ seed for a period of 20 days appeared to excrete more (1.5 vs 1.2 mg/day; SE 0.08; p=0.03) ergovaline in the faeces than those exposed for only 4 days.

CONCLUSIONS: Exposure time to the ergot alkaloids had a limited effect on the route of elimination or the amounts of ergovaline or lysergic acid excreted by horses. The primary alkaloid excreted was lysergic acid, and urine was the major route of elimination. These data will aid future research to improve animals′ tolerance to toxic endophyte-infected tall fescue.