Isolation of the transposable element hupfer from the entomopathogenic fungus Beauveria bassiana by insertion mutagenesis of the nitrate reductase structural gene

A transposable element has been isolated from the entomopathogenic fungus Beauveria bassiana by trapping it in the nitrate reductase structural gene, which has been cloned from this species. The element had inserted in the first exon of the nia gene and appeared to have duplicated the sequence TA at the site of insertion. It was 3336 bp long with 30-bp imperfect, inverted, terminal repeats. The element, called hupfer, contained an open reading frame encoding a 321-amino acid protein similar to the IS630- or mariner-Tc1-like transposases, and a residual sequence of about 2 kb which was not significantly similar to any published sequence. There are fewer than five copies of this transposable element present per genome in the fungus. Received: 12 February 1997 / Accepted: 2 May 1997     

Lysis of bacterioids in the vicinity of the host cell nucleus in an ineffective (fix-) root nodule of soybean (Glycine max)

In nodules of Glycine max cv. Mandarin infected with a nod ⁺fix^- mutant of Rhizobium japonicum (RH 31-Marburg), lysis of bacteroids was observed 20 d after infection, but occurred in the region around the host cell nucleus, where lytic compartments were formed. Bacteroids, and peribacteroid membranes in other parts of the host cell remained stable until senescence (40d after infection). With two other nod⁺ fix^- mutants of R. japonicum either stable bacteroids and peribacteroid membranes were observed throughout the cell (strain 61-A-165) or a rapid degeneration of bacteroids without an apparent lysis (strain USDA 24) occurred. The size distribution of RH 31-Marburg-infected nodules exhibited only two maxima compared with four in wild-type nodules and nodule leghaemoglobin content was found to be reduced to about one half that of the wild type. The RH 31-Marburg-nodule type is discussed in relation to the stability of the bacteroids and the peribacteroid membrane system in soybean.     

Carbon metabolism of Frankia spp. in root nodules of Alnus glutinosa and Hippophaë rhamnoides

The occurrence and localization of enzymes involved in glycolysis, tricarboxylic acid cycle and glyoxylate cycle in root nodules of Alnus glutinosa (L.) Vill. and Hippophaë rhamnoides L. ssp. rhamnoides were studied. The following enzymes, catalyzing reversible steps in the glycolysis, were found in both the endophyte Frankia spp. and the plant cytosol of Alnus nodules: fructose-1,6-diphosphate aldolase, glyceralde-hyde-3-phosphate dehydrogenase, phosphoglycerate kinase and enolase. The enzymes catalyzing irreversible steps in glycolysis, viz. hexokinase and pyruvate kinase, were detectable only in the plant cytosol. Similar results were obtained with nodule homogenates of Hippophaë. This indicates the absence of a complete glycolysis in the endophyte. Vesicle clusters of the nodule endophyte of Alnus contained various dehydrogenases of the tricarboxylic acid cycle and showed activity of glutamate oxaloacetate transaminase. Respiration studies showed that vesicle clusters take up oxygen when supplied with NAD, glutamate and malate together. No oxygen uptake was found when any of these compounds was omitted. Vesicle clusters from both Alnus and Hippophaë nodules showed no detectable activity of the glyoxylate cycle enzymes isocitrate lyase and malate synthase. Since these enzymes are known to be present in Frankia Avcll, when grown in a medium with Tween 80 as carbon source, it is suggested that the glyoxylate cycle enzymes are repressed in the root-nodule symbioses.     

Charakterisierung extrazellulärer proteine und enzyme aus pektinkulturfiltraten von Botrytis cinerea

Extracellular proteins from Botrytis cinerea CBS 144.55 were separated by use of isoelectric focusing in polyacrylamide gel and thin layer isoelectric focusing. In addition to the protein pattern, the activities of protease, amylase, cellulase, polygalacturonase, pectinesterase and glycosidases were determined.     

Benomyl Tolerance of Ten Fungi Antagonistic to Plant-parasitic Nematodes

Ten strains of fungi were tested for tolerance to the fungicide benomyl. Verticillium chlamydosporium strain 2 did not grow in the presence of benomyl; Drechraeria coniospora strains 1 and 2 and Chaetomium sp. tolerated only 0.1 μg benomyl/ml medium; Acremonium bacillisporum, an unidentified fungus, and Phoma chrysanthemicola uniformly grew at 1 μg/ml, but some hyphae grew at higher benomyl concentrations; Fusarium sp. tolerated 475 μg/ml, but some hyphae grew on medium amended with 1,000 μg/ml; Verticillium lecanii and V. chlamydosporium strain 1 routinely tolerated 1,000 μg/ml. Fungi generally grew more slowly at higher than at lower benomyl concentrations. Strains with elevated tolerance to benomyl were selected from Acremonium bacillisporum, Drechmeria coniospora, Fusarium sp., and an unidentified fungus. These strains retained the increased tolerance after repeated transfers on unamended medium.     

Effects of Rapeseed and Vetch as Green Manure Crops and Fallow on Nematodes and Soil-borne Pathogens

In a rapeseed-squash cropping system, Meloidogyne incognita race 1 and M. javanica did not enter, feed, or reproduce in roots of seven rapeseed cultivars. Both nematode species reproduced at low levels on roots of the third crop of rapeseed. Reproduction of M. incognita and M. javanica was high on squash following rapeseed, hairy vetch, and fallow. The application of fenamiphos suppressed (P = 0.05) root-gall indices on squash following rapeseed, hairy vetch, and fallow; and on Dwarf Essex and Cascade rapeseed, but not Bridger and Humus rapeseed in 1987. The incorporation of 30-61 mt/ha green biomass of rapeseed into the soil 6 months after planting did not affect the population densities of Criconemella ornata, M. incognita, M. javanica, Pythium spp., Rhizoctonia solani AG-4; nor did it consistently increase yield of squash. Hairy vetch supported larger numbers of M. incognita and M. javanica than rapeseed cultivars or fallow. Meloidogyne incognita and M. javanica survived in fallow plots in the absence of a host from October to May each year at a level sufficient to warrant the use of a nematicide to manage nematodes on the following susceptible crop.     

The effect of introducing the aphid-pathogenic fungus Erynia neoaphidis into populations of cereal aphids

The aphid-pathogenic fungus Erynia neoaphidis, as dried fungus-infected aphids, was applied to caged plots of winter wheat infested with cereal aphids at two sites, one in Hertfordshire and the other in Hampshire, in 1983. In each trial, the fungus became established in the aphid populations in the treated plots even though conditions were drier than average and therefore sub-optimal for fungus spread. Treatment applied in the third week of June increased the proportion of infected aphids more than that applied two weeks later at one site, and the early application was the only treatment to have an obvious effect at the other. In spite of the observed effect of treatments on the proportion of infected aphids, the fungus failed to reduce the numbers of aphids relative to those in untreated plots, chiefly because in these plots many aphids were killed by fungi of the same species as that introduced and other related species from natural sources. Artificial introduction of E. neoaphidis acts too slowly and unpredictably to be likely to form a practical alternative to conventional insecticides for cereal aphid control.