Assessment of biological and molecular variability between and within field isolates of Plasmodiophora brassicae

Plasmodiophora brassicae is an obligate biotroph that causes clubroot, one of the most damaging diseases of crucifers. Differential cultivars and random amplified polymorphic DNA markers were used to assess the extent of genetic diversity among nine single-gall populations of P. brassicae and 37 single-spore isolates (SSI) derived from four of those field samples. Isolates were classified into eight pathotypes, and each isolate was associated with a unique molecular genotype. Virulence and DNA polymorphisms were detected within and between field isolates, and among SSIs from different pathotypes, hosts and geographical origins. The relatively high level of genetic diversity among field isolates was similar to that among SSIs derived from a single-club field isolate. Molecular and pathogenicity-based classifications were not clearly correlated, but isolates belonging to pathotype P1 were clustered. Two RAPD markers were specific to pathotype P1. The finding that genetic differences can occur in P. brassicae field isolates will be an important consideration in resistance genetic studies and in choosing breeding strategies to develop durable clubroot resistance.     

Homogenization conditions affect the oxidative stability of fish oil enriched milk emulsions: oxidation linked to changes in protein composition at the oil-water interface

Fish oil was incorporated into milk under different homogenization temperatures (50 and 72 degrees C) and pressures (5, 15, and 22.5 MPa). Subsequently, the oxidative stability of the milk and changes in the protein composition of the milk fat globule membrane (MFGM) were examined. Results showed that high pressure and high temperature (72 degrees C and 22.5 MPa) resulted in less lipid oxidation, whereas low pressure and low temperature (50 degrees C and 5 MPa) resulted in faster lipid oxidation. Analysis of protein oxidation indicated that especially casein was prone to oxidation. The level of free thiol groups was increased by high temperature (72 degrees C) and with increasing pressure. Furthermore, SDS-PAGE and confocal laser scanning microscopy (CLSM) indicated that high temperature resulted in an increase in beta-lactoglobulin adsorbed at the oil-water interface. This was even more pronounced with higher pressure. Less casein seemed to be present at the oil-water interface with increasing pressure. Overall, the results indicated that a combination of more beta-lactoglobulin and less casein at the oil-water interface gave the most stable emulsions with respect to lipid oxidation.     

Enhanced resistance to cattle grub infestation (Hypoderma lineatum de Vill.) in calves immunized with purified hypodermin A, B and C plus monophosphoryl lipid A (MPL).

The influence of an antigen-specific cellular and humoral immune response, stimulated by immunization, on survival of a challenge infestation of Hypoderma lineatum was investigated. Calves immunized with a purified combination of hypodermin A, B and C plus monophosphoryl lipid A (MPL) developed a strong antigen-specific cellular immune response by completion of the immunization schedule which persisted to 12 weeks post-infestation. Responsiveness of peripheral blood lymphocytes to the mitogens concanavalin A and pokeweed was also elevated at 4 and 12 weeks post-infestation. Western blot analysis at the time of maximum grub counts demonstrated that immunized calves responded to hypodermin A, B and C while those receiving only MPL or infested controls responded only to hypodermin B and C. The antigen-specific antibody response as measured by ELISA at maximum grub count was significantly higher in vaccinated calves than in infested controls while the response in calves receiving only immunostimulator was also significantly elevated. Immunized (antigen plus MPL) calves produced 5.0 +/- 6.9 grubs per animal which successfully pupated while those receiving MPL alone produced 16.4 +/- 6.1 and infested controls produced 32.2 +/- 10.9 grubs per animal.