Genetic variation at 59 protein coding loci (16 polymorphic) and 25 microsatellite loci was analysed for 11 indigenous south‐east Asian goat populations, and the Australian feral population, to determine the magnitude of genetic differentiation and the genetic relationships among the populations. Significant deviations from Hardy–Weinberg equilibrium were detected in one or more populations for eight of the nine protein loci with codominant alleles, and for microsatellites for all except the two Sri Lankan populations and for all but four loci. For both marker types, average inbreeding coefficients (FIS) were exceptionally high. Heterogeneity of deviations from Hardy–Weinberg equilibrium for the microsatellites showed no differences for among loci within populations as compared with among populations within loci. For protein loci, however, the former was higher, indicating selection affecting allele frequencies at some loci. The variance among protein loci was significantly higher than among microsatellite loci, further indicating selection at some protein loci. There was significant differentiation among populations for both protein and microsatellite loci, most likely reflecting the geography of south‐east Asia, and the presumed spread of goats throughout the region. Phylogenies derived from pair‐wise genetic distance estimates show some similar clustering for the microsatellite and protein based trees, but bootstrap support was generally low for both. A phylogeny based on the combined set of 38 protein and microsatellite loci showed better consistency with geography and higher bootstrap values. The genetic distance phylogeny and the Weitzman diversity tree derived from microsatellite data showed some identical clusters, and both identified the Ujung Pandang and Australia populations as contributing most to overall genetic diversity.

To evaluate whether the location of bacterial endophyte communities contributes to disease resistance in potato tubers (Solanum tuberosum), the population density, biodiversity and antibiotic activity of endophytic bacteria was examined from the tuber peel (periderm plus top 3 mm of tissue) of four cultivars (Russet Burbank, Kennebec, Butte and Shepody). There were no significant differences for population density of bacteria among the layers of peel examined and no cultivar × peel layer interaction. Endophytic bacteria from several layers of peel were challenged in in vitro bioassays to the soil-borne plant pathogens Fusarium sambucinum, Fusarium avenaceum, Fusarium oxysporum and Phytophthora infestans (mating types A1 and A2). In general, antibiosis of bacterial endophytes against these pathogens was significantly higher (P ¼ 0·01) in isolates recovered from the outermost layer of tuber peel and decreased progressively toward the centre of the tuber. Antibiosis against P. infestans was variable, with a progressive decrease in antibiotic activity from outer to inner layers of peel occurring in cvs Russet Burbank and Kennebec only. For antibiosis there were significant cultivar × peel, and cultivar × pathogen interactions (P ¼ 0·01). In all cases the inhibitory activity of endophytic bacteria was significantly greater (P ¼ 0·01) against the A1 than the A2 mating type of P. infestans. In four of seven cases, where the same species of bacteria were recovered from all three peel layers, antibiosis to pathogens decreased significantly (P ¼ 0·01) with depth of recovery (from the periderm to inside the tuber), indicating that in certain communities of endophytic bacteria, defence against pathogens may be related to bacterial adaptation to location within a host and may be tissue-type and tissue-site specific.

The catalysis of methyl viologen radical cation (MV+•) decay reactions by gold sol, stabilized by either poly(vinyl sulfate) (PVS) or poly(vinyl alcohol) (PVA), was studied by pulse radiolysis. Stabilization of the sol by PVS eliminates the hydrogen evolution reaction as a pathway for MV+• decay. This is shown to be due to dimerization of MV"1"• (to the biradical) in the potential field of the polyelectrolyte. On PVA-stabilized sols, the hydrogen evolution reaction is a major pathway although side reactions (probably hydrogenation) interfere to a large extent. The rate of adsorption of MV+• on PVA-stabilized sol is controlled by the diffusion of MV"1"• to the gold particle. Subsequent reactions of protonation and electrochemical desorption, (Au)c""Hm + H30+ -*• (Au)c('1_1)"Hm_1 + H2 + H20, on a slower time scale are the rate-determining steps at the pH range and catalyst concentration used. At higher catalyst concentrations interparticle reaction is invoked to explain the dependence on [Au].(PVS) gold sol has been described previously.12 The other sol was stabilized by poly(vinyl alcohol) (PVA, Polysciences, Inc., 133 000 molecular weight). Approximately 100 mg of HAuC14 was dissolved in 500 mL of 0.1% PVA, and the pH adjusted with NaOH to ~11. CO gas was then bubbled through the solution for 10 min at room temperature. The resultant sol was then acidified with HC104 to pH 2.5 and then boiled for 1 h to expel CO or C02. The sol thus obtained had a spectrum similar to that of the Au/PVS sol previously described.12 Both sols were found

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