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381.
Infection by a Drechslera sp. (perfect stage, Pyrenophora chaetomioides (Speg.)), isolated from Bromus sterilis , killed B. sterilis , B. commutatus and B. secalinus. B. diandrus and B. hordeaceus were both infected but not killed. Successful infection required a 24-h dew period. Reduction of the dew period to 8 h significantly reduced the infection of all Bromus spp. tested as determined by leaf necrosis. Inoculation with a low inoculum concentration (2 104 conidia/ml) produced little dry weight reduction, but at 2 105 conidia/ml with an 8-h dew period the dry weights of B. commutatus , B. diandrus , B. secalinus and B. sterilis were reduced by 11-25%. Extending the dew period to 24 h resulted in 77% mortality of B. sterilis and 93% mortality of B. commutatus and B. secalinus. 相似文献
382.
R W Newbert B Barton P Greaves J Harper G Turner 《Journal of industrial microbiology & biotechnology》1997,19(1):18-27
Several commercially improved strains of Penicillium chrysogenum have been shown to carry amplifications of the entire penicillin biosynthesis gene cluster. Analysis previously carried
out using the strain BW 1890 has here been extended to the characterisation of other members of the SmithKline Beecham strain
improvement series. We have determined the length of the amplicon to be 57.4 kb and shown a general increase in copy number
and penicillin titre through the series. Sequence analyses of the promoter regions of the acvA, ipnA and aat genes in the high titre strain BW 1901, and comparisons with wild-type sequences have not identified any potentially titre-enhancing
mutations. In addition, cDNA screening has failed to identify any further transcribed elements within the co-amplified region.
The homogeneity of hybridisation patterns and the identification and analysis of a single copy revertant has shown that the
amplification is of a direct tandem nature and we propose a model of chromatid misalignment and recombination as its mode
of generation. Hybridisation analysis of penicillin non-producing mutants has indicated the loss, in all those investigated,
of the entire penicillin biosynthesis gene cluster, similarities between the deletion junctions in these strains and comparison
with previously published data indicating the presence of recombinogenic regions flanking the penicillin biosynthesis gene
cluster.
Received 05 November 1996/ Accepted in revised form 25 April 1997 相似文献