The effect of component number on Rhynchosporium secalis infection and yield in mixtures of winter barley cultivars

Mixtures of winter barley cultivars containing up to six components were grown over three years with and without fungicide treatment. Yield increases were recorded for mixtures compared with the mean of their monoculture components and there was a significant trend towards greater benefit from increased number of components. These benefits were partially attributable to a corresponding increase in control of Rhynchosporium secalis as component number increased. The potential for exploitation of mixtures in cereals for control of splash-dispersed pathogens is discussed.     

Attempted somatic hybridization of Puccinia striiformis f. sp. tritici and P. striiformis f. sp. hordei

Attempts were made to produce somatic hybrids between isolates of Puccinia striiformis f. sp. tritici and f. sp. hordei. A mixed infection was produced on a common susceptible barley host, Fong Tien, using white-spored isolates of P. striiformis f. sp. tritici and yellow-spored isolates off. sp. hordei. Selection was made for non-parental spore colour on selective wheat and barley hosts, and variants thus isolated were analysed for virulence markers, and for isozyme and double-stranded RNA (dsRNA) markers, all of which clearly differentiated the parental isolates. Two white-spored (non-parental) isolates were found on the selective barley host which otherwise resembled the parental f. sp. hordei isolate in virulence, isozyme and dsRNA markers. The most likely explanation of the origin of these isolates is mutation to white spore colour in the f. sp. hordei isolate.     

Coxofemoral Luxation in the Dog and Cat

The medical records from 95 cases of coxofemoral luxation in dogs and cats were reviewed. Unilateral craniodorsal luxation was most common, (78.1% of dogs, 72.7% of cats). Trauma from being struck by an automobile was the most frequent cause (59.0%). Treatment was closed (manual) or open (surgical) reduction. The failure rate following single closed reduction was 64.8%. The surgical reduction procedure included capsular repair (capsulorrhaphy) via a craniolateral approach to the hip or via trochanteric osteotomy or gluteal tenotomy. The success rate following reduction via the craniolateral approach was 82%; no failure was recorded with trochanteric transposition, but reluxa-tion followed the single gluteal tenotomy. The Ehmer sling was the most common external fixation and was kept in place an average of 12.5 days. Thirty-three animals were available for follow-up, and no difference was recorded in limb function between the two groups of animals treated by closed vs surgical reduction. Patients with degenerative joint disease at the time of luxation were less likely to be successfully reduced; 64.3% of these animals were eventually treated by femoral head and neck excision. Thirty-eight patients had associated major injuries. Long-term follow-up results were better in those patients with concomitant orthopedic injuries than in those without other injuries.     

Detection of components of partial resistance to mildew (Erysiphe graminis f.sp. hordei) incorporated into advanced breeding lines of barley using measurement of fungal cell wall sterol

Characters for partial resistance to mildew ( Erysiphe graminis f.sp. hordei ) derived from primitive barley lines were tested and found to have been transmitted to F9 progeny of crosses with the susceptible cultivar Golden Promise with varying degrees of efficiency, and putative transgressive segregation was observed. Derived sterol extracts from mildew cell walls were used, in conjunction with infection frequency data, to quantify the mildew present, and this sterol was characterized as being of MW 470, probably (3.beta)-ergosta-5,24(28)dienol (C31.H54.0.SI SILANE).     

Canine Axial Skeletal Osteosarcoma A Retrospective Study of 116 Cases (1986 to 1989)

Axial skeletal osteosarcomas were evaluated retrospectively in 116 dogs. Thirty-one tumors occurred in the mandible, 26 in the maxilla, 17 in the spine, 14 in the cranium, 12 in the ribs, 10 in the nasal cavity and paranasal sinuses, and 6 in the pelvis. Medium-sized and large dogs were most commonly affected. Females outnumbered males 2.1:1, but this varied with tumor location. The mean age was 8.7 years. Osteosarcomas of the rib occurred in significantly younger dogs (mean age, 5.4 years) than osteosarcomas at any other axial skeletal site. Pulmonary metastasis was diagnosed radiographically in 11.1% of the dogs. The median survival for dogs treated surgically was 22 weeks, the 1-year survival was 26.3%, and the 2-year survival was 18.4%. The tumor recurrence rate was 66.7%. Most dogs (79.6%) died or were euthanatized for problems associated with the primary tumor.     

Modelling the spread of fungal diseases using a nearest neighbour approach: effect of geometrical arrangement

A discrete model of the nearest neighbour type is used to model the growth and spread of fungal disease in a two-cultivar mixture assuming an unspecialized pathogen. Disease dynamics and dispersal are represented by a spatial, single pathotype version of Gumpert's (1992) model that simulated the temporal evolution of a number of pathotypes on a cultivar mixture. Spore dispersal occurs by discrete rules between a cell and its four orthogonal neighbours in a rectangular grid. Parameters termed transmission efficiency rates control the extent of successful inoculum exchange between two neighbouring cells depending on the cultivars present. Spatially averaged disease progress curves are computed for regular block and strip patterns in addition to the mean curve for twenty 1:1 random mixture patterns. These sets of curves are exhibited relative to the appropriate pure stand comparison for a range of auto- and cross-deposition parameters. We conducted simulations for uniform initial infection and also averaged over 20 random initial infection patterns at a comparable mean level. In the former case, provided the ratio of cross-deposition to auto-deposition is high enough and the disease progress curves take sufficiently long to reach their saturation value, the ranking of the geometrical patterns can eventually be interpreted once initial oscillations have subsided. The geometry with the largest proportion of links between neighbouring cells of different cultivar type generally corresponds to the lowest average disease level, but not for averaged simulations based on random initial infection patterns.