Pathogenic diversity of Didymella rabiei isolates from southern Alberta,Canada

Journal of Plant Diseases and Protection - Sixty-three isolates of Didymella rabiei collected from southern Alberta were analyzed for pathogenic variability using six differential chickpea...     

Impact of Foliar Diseases on Photosynthesis, Protein Content and Seed Yield of Alfalfa and Efficacy of Fungicide Application

Foliar pathogens attack alfalfa wherever the crop is grown, but their impact, especially on seed production, is poorly understood. In greenhouse trials, leaf spot injury caused by inoculation with various pathogens reduced the crude protein content of infected alfalfa leaves by 22% compared with a healthy control. There was a negative relationship between disease injury and the photosynthetic efficiency of alfalfa plants, as determined by measuring chlorophyll fluorescence in leaves from inoculated vs. non-inoculated seedlings. In field trials at two sites in Alberta from 2001 to 2003, inoculation with Phoma medicaginis increased disease incidence in four of six trials, Phoma sclerotioides increased incidence in four of five trials, and Leptosphaerulina trifolii and Stemphylium botryosum increased incidence in two of six trials. There was a trend for inoculation treatments to reduce seed yield, despite high levels of background infection by indigenous pathogens. The fungicides benomyl and propiconazole inhibited radial growth of Phoma spp. in vitro and reduced disease incidence in inoculated greenhouse experiments. In field trials, applications of benomyl and propiconazole reduced disease incidence, but did not always increase seed yield.     

Genetic variation in Fusarium avenaceum causing root rot on field pea

Isolates of Fusarium spp. were recovered from the roots of field pea (Pisum sativum) collected from 15 commercial fields in Alberta, Canada. Most of the isolates (75 out of 96) were identified as F. avenaceum, based on morphology, phylogeny and species‐specific PCR amplification. Molecular differences in the F. avenaceum isolates were detected based on putative mating type, and on ITS and CPN60 sequences. MAT‐1 and MAT‐2 were equally distributed among the isolates. Phylogenetic analysis based on ITS and CPN60 sequences clustered most of the F. avenaceum isolates into a single group. In some cases, isolates with low aggressiveness clustered together in additional groups. There was no correlation between phylogenetic profile and either mating type or geographic origin. This population of F. avenaceum has a low level of genetic variation and consists of isolates derived from the two mating types. Isolates with low aggressiveness are also retained in the population.     

Evaluation of visible implant elastomer tags for pathogenesis research in Nile tilapia (Oreochromis niloticus)

Two different colours (red and green) of visible implant elastomer (VIE) were used in Nile tilapia (Oreochromis niloticus). The visibility, location and retention of the VIE tags was investigated and any adverse effects on fish survival and growth determined. The use of VIE tags for monitoring individual fish during a bacterial challenge with either Streptococcus agalactiae or S. iniae was also studied. The results showed that VIE treated fish were lighter but not shorter than the non‐tagged control fish and that tagging caused no mortality. The retention of tags was better at the base of pectoral fin followed by the nasal area, lower abdomen, upper abdomen and branchiostegal rays inside the operculum. During the bacterial challenge experiment individual animals could be easily identified using the VIE tags. In this preliminary study, VIE tagging appears suitable for Nile tilapia research, as with other fish species, and could be a novel method to identify individual animals during microbial pathogenesis studies.     

Housing and Environment for Dairy Calves

Many cases of poor health in calves have been traced to bad management and inadequate ventilation in the calf nursery. Important management principles for improved calf health include calf housing isolated from the adult herd and periodic depopulation and sanitizing of the calf nursery area. In good weather, low-cost calf rearing portables such as the “calf hutch” can provide alternative housing during the cleanup period.

Calf nursery ventilation systems must have flexibility to give the full winter-to-summer range of controlled ventilation rates and critical air inlet adjustments. Earlier recommendations were for three stepped ventilation rates of 3.3, 6.6 and 24 L/s per calf to cover the range from cold winter to warm summer weather. Later recommendations are for a simpler two stepped fan system starting at 6.7 L/s (continuous winter rate) and increasing to 50 L/s for temperature control in warm to hot weather.

Even with the best insulated construction, increased supplementary heating is required to support this increased continuous winter ventilation. To save energy the heating must be controlled to stop before the higher-rate ventilation starts. Other design features for more uniform temperatures and improved calf nursery ventilation include: 1) preheating the ventilation air before it enters the calf room, 2) distributing air to the ceiling with round holes and adjustable slots adjusted to give at least 4 m/s inlet velocity, 3) using a properly sized centrifugal fan running continuously to exhaust air from near the floor in winter and 4) protecting air intakes and fan openings from the effects of wind. Air recirculation systems and variable-speed fans are not recommended.

     

The pathology of chronic erosive dermatopathy in Murray cod, Maccullochella peelii peelii (Mitchell)

Chronic erosive dermatopathy (CED) is a disease of intensively farmed Murray cod in Australia that has been reported in association with the use of groundwater (mechanically extracted from shallow boreholes) supplies. CED results in focal ulceration of the skin overlying sensory canals of the head and flanks. Trials were conducted at an affected fish farm to study the development of the condition, both in Murray cod and in goldfish, and also to assess the reported recovery of lesions when affected fish were transferred to river water. Grossly, lesions began after 2-3 weeks with degeneration of tissue at the periphery of pores communicating with the sensory canals. Widening of these pores along the axis of the canals resulted from a loss of tissue covering the canal. Histopathologically, hyperplasia of the canal epithelial lining was seen after 3 weeks in borehole water and subsequent necrosis and sloughing of this tissue resulted in the loss of the canal roof. Canal regeneration occurred when fish were transferred from borehole water into river water. The lack of lesions in other organs and the pattern of lesion development support exposure to waterborne factors as the most likely aetiology.     

The implications of a feelings-based approach to fish welfare: a reply to Arlinghaus et al.

The welfare of fish is a topic of increasing debate touching on a number of complex scientific and ethical issues and constructive dialogue between groups with differing approaches to the topic requires mutual understanding from both perspectives. In a recent review aimed at stimulating debate on this topic, Arlinghaus et al. (2007) explore the question of fish welfare in the particular context of recreational angling, by means of a critique of a review of fish welfare in general written by ourselves ( Huntingford et al. 2006 ). We entirely agree with the desirability of debate on this topic and recognize a number of valuable qualities in the commentary by Arlinghaus et al. However, we argue that the critique has some serious flaws. In the first place, by rejecting a feelings‐based approach to welfare, it fails to address the aspect of welfare that is at the heart of much legitimate public concern. Secondly, while advocating an objective, scientific approach to fish welfare, Arlinghaus et al. fail to present their own agenda (that recreational angling is morally acceptable) in a transparent way. Thirdly, they seriously misrepresent the position taken in Huntingford et al. (2006) on a number of important issues. In this reply, we address these points and then discuss briefly the areas of agreement and constructive disagreement between the two reviews.