The influence of crown rust (Puccinia coronata) on tiller production and survival of perennial ryegrass (Lolium perenne) plants in simulated swards

Populations of Aberystwyth S23 and S24 ryegrass tillers were individually labelled and harvested at intervals to follow their life histories and productivity in response to the effect of infection with crown rust at two levels of nitrogen fertilization.
The number of tillers in a population was reduced as a result of infection with crown rust. Increased rates of tiller death due to the pathogen occurred throughout the population age-range and were most pronounced in the youngest tillers. Population changes were evident following infection and continued to be apparent in the following spring. The disease caused alterations in sward age structure, leading both to a higher proportion of older tillers in the more rust-damaged treatments and to a decrease in the weight of the herbage produced. It is concluded that rust infection of a sward may lead to changes in population structure with long-term yield effects, in addition to the immediate direct yield reductions commonly reported. The significance of these results to the ecological and agronomic balance of grassland is discussed.     

Relationships between the spatial pattern and number of apothecia of Sclerotinia sclerotiorum and stem rot of soybean

Relationships between the spatial patterns and numbers of apothecia of Sclerotinia sclerotiorum and incidence of sclerotinia stem rot of soybean (Glycine max) were investigated in a field plot in 1981 and 1982. Apothecia and disease were both spatially aggregated and were most consistently described by the negative binomial distribution, although the Poisson-binomial and logarithmic with zeros distributions sometimes gave significant fits to data. Numbers of apothecia and disease incidence were correlated within quadrats of 1.4 m² (r = 0.04-0.57), 36 m² (r = 0.44-0.87) and 108 m² (r = 0.44-0.99). The results suggest that disease incidence was determined primarily by inoculum produced within the field. This information may be important in developing models for disease production.     

Unusual or interesting records of plant pathogenic Oomycetes

The following records from the UK are discussed: Peronospora grisea on Hebe gauntlettii (forming oospores), H. elliptica x pimelioides cv. Carl Teschner and H. hulkeana ; Peronospora fragariae on Potentilla recta ; Peronospora hariotii on Buddleia davidii cv. Pink Delight and B. globosa ; Pythium tracheiphilum on Lactuca sativa . The following records from other countries are discussed: Phytophthora erythroseptica var. erythroseptica on Cymbidium sp. in Western Australia; Phytophthora palmivora on Zizyphus jujuba in Taiwan (a new record on this host); Plasmopara halstedii on Arctotis sp. in New Zealand (a new record of this species for Australasia).     

Surgical correction of the tetralogy of Fallot in a dog

Tetralogy of Fallot is the commonest cause of cyanotic congenital heart disease in the dog. Previous attempts at surgical treatment have been confined to palliative systemic to pulmonary arterial shunts. We describe the clinical presentation, cardiac catheterization and angiographic diagnosis of Fallot's tetralogy in a young Boxer dog. Total intracardiac correction was successfully embarked upon with the use of cardiopulmonary by-pass. Postoperatively there was a marked improvement in his exercise tolerance. Intermittent syncopal attacks developed several months after discharge from hospital and the dog died suddenly two years after operation.