Resistance to ACCase-inhibiting herbicides and isoproturon in UK populations of Lolium multiflorum: mechanisms of resistance and implications for control

Herbicide-resistant Lolium multiflorum (Italian rye-grass) was first reported in the UK in 1993 and had been confirmed on 25 farms by 1999. In this study, resistance to five herbicides belonging to the aryloxyphenoxypropionate, cyclohexanedione and phenyl-urea classes was determined in six populations of L multiflorum from the UK under glasshouse and simulated field conditions. Glasshouse conditions tended to exaggerate the degree of resistance, but experiments performed in both environments detected resistance in four populations of L multiflorum. Four populations (Essex A1, Lincs A1, Wilts B1, Yorks A2) were resistant to diclofop-methyl, fluazifop-P-butyl, tralkoxydim and partially resistant to isoproturon, but only the population from Yorkshire (Yorks A2) showed resistance to cycloxydim. Biochemical analyses of acetyl coenzyme A carboxylase (ACCase) activity, oxygen consumption by thylakoids, diclofop metabolism and glutathione S-transferase activity showed that, in three of the resistant populations, an enhanced rate of herbicide metabolism conferred resistance. This is the first report world-wide of an enhanced metabolism mechanism of diclofop resistance in L multiflorum. In the Yorks A2 population, an insensitive ACCase was detected (target-site resistance) which also conferred cross-resistance to all of the other ACCase inhibitors investigated.     

Surface Hydrophobicity and Surface Rigidity Induce Spore Germination in Colletotrichum graminicola

ABSTRACT We investigated the relationship between physical characteristics of artificial surfaces, spore attachment, and spore germination in Colletotrichum graminicola. Surface hydrophobicity and surface rigidity were both signals for breaking dormancy and initiating spore germination, but spore attachment alone was not an important inducing signal. The presence of a carbon source overrode the necessity for a rigid, hydrophobic substrate for spore germination. Spore attachment was typically stronger to more hydrophobic surfaces, but certain hydrophilic surfaces also proved to be good substrates for spore attachment. In contrast to spore germination, appressorial induction was more dependent on attachment to a rigid substrate than it was on surface hydrophobicity. Appressoria were induced efficiently on hydrophilic surfaces, as long as there was significant conidial attachment to those surfaces.     

Systemic mycosis due to Aspergillus deflectus in a dog

A 4-year-old, entire female, German Shepherd Dog was referred with a 3-month history of right foreleg lameness that partially responded to nonsteroidal anti-inflammatory and antimicrobial therapy. The bitch lost weight, was polydipsic and had reduced exercise tolerance. On referral, the animal was in poor condition, pyrexic and exhibited moderate pain on full extension of the right shoulder. Blood, urine and joint fluid were obtained and radiographs were taken of the right shoulder and chest. The bitch was lymphopaenic, hyperfibrinogenaemic, hyperglobulinaemic, mildly azotaemic, mildly proteinuric and isosthenuric. Branching fungal hyphae were present in the urine. On radiography, the thorax contained a large ventral mediastinal mass and the humeral head had extensive areas of radiolucency. An aspirate from the right humeroscapular joint exhibited branched fungal hyphae and numerous neutrophils and macrophages. A diagnosis of disseminated mycosis was made and euthanasia was performed. At necropsy, numerous caseating granulomas were present, especially in the kidneys, adrenal glands, heart and lymph nodes. Extensive osteomyelitis involved the head of the right humerus, the sternebrae and the fifth intervertebral disc. Fungal hyphae were detected in sections of granulomas in all affected organs and a diagnosis of disseminated fungal granulomatosis was made. Aspergillus deflectus was readily isolated from affected lymph nodes, but confirming its identity as A deflectus using standard procedures proved difficult. The identity of the fungus was finally confirmed by sequencing part of the 185 rRNA of the isolate. This is the first report in Australia of a disseminated mycosis caused by A deflectus. Previously, the involvement of A deflectus as a cause of disseminated mycosis was limited to 5 cases from the West Coast of the USA, four of which occurred in German Shepherd Dogs.     

Genetic diversity of weeds growing in continuous wheat

Genome fingerprinting by simple sequence repeat (SSR)-anchored polymerase chain reaction (PCR) was used to analyse diversity in four weed species ( Alopecurus myosuroides Huds., Medicago lupulina L., Stellaria media (L.) Vill. and Aphanes arvensis L.) growing in the Broadbalk long-term wheat experiment. The experiment is made up of individual plots, to which different fertilizer regimes have been applied annually for more than 150 years. Sixteen polymorphic loci were analysed in the obligate outcrosser A. myosuroides (24 plants sampled on each of four plots); the proportion of total diversity caused by differences between populations (G_st) was low (0.02). Twelve loci were analysed in the self-pollinating species M. lupulina (24 plants sampled on each of four plots, G_st=0.12) and S. media (24 plants sampled on each of three plots, G_st=0.11); and 11 loci in the apomict A. arvensis (24 plants sampled on each of four plots, G_st=0.19). There was no relationship between the geographic distances separating plots and the genetic distances between samples from the weed populations growing on each plot. Soil fertility had an effect on molecular diversity in S. media : plants growing on low-nitrogen showed divergence from those sampled on high-nitrogen plots, which contained slightly more diversity.     

Carbon dioxide compensation points in related plant species

Both high and low C0(2) compensation concentrations were found in the plant genera-Panicum, Cyperus, and Euphorbia. Within each genus, however, high and low compensations were found in different subgenera. Thus, they may not be genetically closely related. No significant differences in CO(2) compensation were found among 100 genetic lines of Triticum aestivum L. or among 20 lines of Hordeum vulgare L.     

Impacts of ski-development on ptarmigan (Lagopus mutus) at Cairn Gorm, Scotland

This paper reports adverse impacts on numbers and breeding success of ptarmigan (Lagopus mutus) in 1967-1996 at a ski area in the Cairngorms massif, where ptarmigan normally show 10-year population cycles. An influx of carrion crows (Corvus corone), generalist predators, followed the development. On the most developed area near the main car park, ptarmigan occurred at high density but then lost nests to frequent crows, reared abnormally few broods, died flying into ski-lift wires and declined until none bred for many summers. On a nearby higher area with fewer wires, ptarmigan lost nests to frequent crows and reared abnormally few broods, but seldom died on wires. Adult numbers declined and then became unusually steady for over two decades, with no significant cycle. On a third area further from the car park, ptarmigan lost fewer nests to the less frequent crows but bred more poorly than in the massif’s centre, and showed cycles of lower amplitude than there. On a fourth area yet further away, with few or no crows, ptarmigan bred as well as in the massif’s centre and showed cycles of the same amplitude as there.     

The site of action of the crossability genes (Kr 1, Kr 2) between Triticum and Secale. I. Pollen germination,pollen tube growth,and number of pollen tubes

Summary Seven genotypes of common wheat (Triticum aestivum L.) were crossed with rye (Secale cereale L.) in order to find the site or sites of action of the crossability genes, Kr ₁ and Kr ₂, of wheat. The data obtained, by fluorescence microscopy, were compared to the controls (wheat x wheat). The results indicate that the crossability genes have little effect on pollen germination and on the time taken for the pollen tubes to reach the microphyle, irrespective of their crossabilities with rye. The number of pollen tubes reaching the microphyle is, however, affected by the Kr-genes, as high crossable genotypes have more pollen tubes than the low crossable ones. There was a high correlation between the mean number of pollen tubes at the micropyle with seed set, which also reflects the crossability. The Kr-genes seem to manifest themselves in the retardation and inhibition of pollen tube growth between the style base and the top of the embryo sac, where the effect is most distinct in the low crossable genotypes.