Pesticide Resistance Strategies and Tactics for Management (1986) / Chapter Skim
Currently Skimming:
Plant Pathogens
Plant Pathogens
Pages 100-110
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 100... ...
At present, effective antiviral agents to control plant viruses in agriculture are not available. Current chemical control of plant pathogenic bacteria and other prokaryotes is based only on copper and the antibiotics streptomycin and oxytetracycline (Jones, 19821.
|
From page 101... ...
The ability of fungi to render fungicides ineffective varies greatly, however, depending mainly on the fungicide (Georgopoulos, 19841. Appropriate Variability Apparently Unavailable The effectiveness of most protectant agricultural fungicides has remained unchanged after decades of use.
|
From page 102... ...
Copper fungicides probably have retained the same effectiveness in controlling plant pathogenic fungi, because the genes conferring resistance to copper are not available to these fungi. Similarly, no genes substantially affect the sensitivity of fungi to sulfur, dithiocarbamates, phthalimides, quinones, chlorothalonil, or any of a few other, less important protectant fungicides.
|
From page 103... ...
and to the ergosterol biosynthesis inhibitors (van Tuyl, 1977~. The involvement of several resistance genes and of modifiers maintains a unimodal sensitivity distribution in field populations even after many exposures.
|
From page 104... ...
In the nonpathogen Aspergillus nidulans, a major gene for resistance to these fungicides codes for p-tubulin, one of the subunits of the tubulin molecule. Mutational modifications of this subunit can be recognized electrophoretically and by the tubulin's ability to bind benzimidazole fungicides (this ability is inversely correlated to resistance)
|
From page 105... ...
Single gene-controlled configurational changes of the ribosomes appear to not interfere with normal ribosome functioning. In double mutants, however, where positive interactions result in higher cycloheximide resistance, the presence of two mutant ribosomal components disturbs vital functions of the ribosomes (Vomvoyanni and Argyrakis, 19791.
|
From page 106... ...
In wild-type strains of the nonpathogen Aspergillus nidulans, passive fenar~mol influx results in considerable accumulation that induces an efflux activity that is energy-dependent. In strains of the same organism carrying a mutation for fenar~mol resistance, the efflux activity appears to be constitutive, preventing initial fungicide accumulation within the cells.
|
From page 107... ...
Mutant genes, therefore, affect the efficiency of fungicide excretion from the mycelium (de Waard and Fuchs, 19821. Detoxification or Nontoxipcation Streptomycin resistance in the fireblight pathogen Erwinia amylovora is believed to result from a chromosomal mutation modifying the ribosome (Schroth et al., 19791.
|
From page 108... ...
Although a better knowledge of the genetics and biochemistry of plant pathogenic microorganisms will facilitate future efforts to understand fungicide resistance, scientists must not overweigh present difficulties to achieve their goals. REFERENCES Barak, E., and L
|
From page 109... ...
1982. Tandem gene amplification mediates copper resistance in yeast.
|
From page 110... ...
1980. Thiophene carboxamide fungicides: Structure activity relationships with the succinate dehydrogenase complex from wild-type and carboxin-resistant mutant strains of Ustilago maydis.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.