Leptospira interrogans serovar hardjo is not a major cause of bovine abortion in Victoria

The aim of this study was to determine whether evidence could be obtained of foetal infection with Leptospira interrogans serovar hardjo in aborted foetuses collected from dairy farms. Material from 197 abortions occurring over a wide area of Victoria was collected over 3 years. None of 195 foetal kidney cultures or 7 cultures from membranes was positive for leptospiral organisms. Immunogold silver staining for leptospires was performed on sections of kidneys, lungs or heart from 156 foetuses, with negative results. Evidence of transient leptospiral infection in 11 of 123 foetuses was obtained by foetal heart blood serology. Two isolates of L. interrogans serovar hardjo were obtained from the urine of milking cows. These strains were examined by restriction endonuclease analysis and both were shown to be of the genotype Hardjobovis, as have been all Australian isolates studied so far. It appears that foetal infection with serovar hardjo is not associated with any substantial proportion of bovine abortions in Victoria, in contrast to the situation in Northern Ireland. The apparent absence from Victoria of the pathogenic genotype Hardjoprajitno is a possible explanation.     

Detection of two viruses infecting Narcissus by enzyme-linked immunosorbent assay

The enzyme-linked immunosorbent assay (ELISA) proved sufficiently reliable to detect narcissus tip necrosis virus (NTNV) and arabis mosaic virus (AMV) in Narcissus leaf material provided it was of the right age. Similar trends in virus concentration in leaf samples were indicated by ELISA reactions for both viruses, with highest levels at the start of growth, a decrease during flowering, followed by an increase before levels fell as leaves died. Leaf tip samples consistently provided the highest ELISA reactions at all stages and testing was more reliable from outer, older leaves than inner, younger ones. Best samples for ELISA detection of both viruses were from the tips of older leaves early in the growing season.     

A METHOD FOR THE QUANTITATIVE MEASUREMENT OF ANISOTROPIC PLASMA IN SOIL THIN SECTIONS

A method is described to measure the total amount of anisotropic plasma visible in soil thin sections. The proportion occurring within 15μm of void and skeletal grain surfaces is also measured. The results can be presented as an orientation index.     

THE USE OF ORIENTATION DIAGRAMS IN DESCRIBING PLASMIC FABRICS IN SOIL MATERIALS

Orientation diagrams are used to show differences in the orientation of birefringent domains in the S-matrix, and in sub-cutanic features of the vo-insepic fabric of two West Indian soils. Such orientation diagrams could prove useful in helping to characterize plasmic fabrics.     

Effect of temperature and water variables on the juvenile growth of lucerne and red clover

Plants of three cultivars of lucerne ( Medicago sativa L.) and of red clover ( Trifolium pratense L.) were grown at four levels each of water availability and temperature in all combinations to evaluate these factors as determinants of plant growth. Plants grew in conventional plant growth chambers from age 2 to 4 weeks with the roots held between layers of polyester cloths that held a volume of nutrient solution which was adjusted at 24-h intervals by flushing and blotting the cloths. The experimental design consisted of two growth chamber runs at each of four temperatures. Within each run, water treatments and the species-cultivar combination were arranged In four replicates of a split-plot design with water treatment as whole plot and species-cultivars as subplots.
Plant response variables over all treatments were significant (P < 0·05) for temperature and water for shoot weights, root weights, shoot/root ratios and number of roots. Cultivars within species had no significant difference in response lo the treatments, but species differences were significant for alt response variables except shoot/root ratio.     

Competition among seedlings of phalaris, subterranean clover and white clover in diallel replacement series mixtures

Phalaris, subterranean clover and white clover were grown together in binary, diallel replacement series mixtures at (day/night) 15/10 or 24/19°C under long-day conditions, and cut at 2- or 4-weekly intervals. Analysis of white clover mixtures was confined to 15/10°C due to losses of seedlings prior to imposition of treatments at 24/19°C.
With white clover at 15/10°X, seedling losses occurred after the first harvest, the greater losses occurring in mixtures where subterranean clover was the major component. The de Wit analyses showed that subterranean clover excluded its companions, whereas phalaris and white clover competed for slightly different niches resulting in over-yielding. Gleeson McGilchrist analyses showed that subterranean clover and phalaris were more aggressive than white clover under infrequent cutting, but that white clover was more aggressive as a major than as a minor component of a mixture under frequent cutting. Between phalaris and subterranean clover [he pattern of competition at 24/19°C differed from that at 15/10°C only in the more rapid development of subterranean clover and consequent swing to phalaris dominance.
We conclude that the seedlings of white clover and subterranean clover are suited to combination with phalaris because phalaris is not too aggressive towards white clover, and is tolerant of the aggressiveness of subterranean clover. The survival of only a few seedlings of white clover in mixtures with subterranean clover may be sufficient for long-term growth provided some perennation occurs after the senescence of subterranean clover.