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121.
A general field bioassay for detecting biologically active compounds in plants and insects has been developed and tested for efficacy and sensitivity. Methanolic extracts, in sucrose solution, of 20 plant and six caterpillar species were offered to the ponerine ant Paraponera clavata and the feeding preferences observed. The bioassay resulted in the detection of nine plant and three caterpillar species with ant-deterrent extracts, and 11 plant and three caterpillar species with neutral or attractant extracts. All of the plants showing ant-deterrent characteristics which had been chemically investigated in our laboratory, or for which chemical literature was available, contained secondary metabolites of known deterrence. Both naturally occurring and artificial differences in chemical concentrations could be detected using the bioassay. The method provides a means of screening plants and insects for compounds that are insect anti-feedants or that can modify insect behaviour. 相似文献
122.
Dyer C 《BMJ (Clinical research ed.)》2000,321(7270):1175
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Sexual crosses were used to determine the genetic basis of resistance to the sterol 14 alpha-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae. Three different crosses between sensitive parental strains (22-432 and 22-433 [the concentration required to inhibit growth by 50% (IG(50)) for each was =0.03 mg/liter]) and field isolates from France and New Zealand with differing levels of resistance (PR11 [IG(50) = 0.5 mg/liter], PR1 [IG(50) = 1.0 mg/liter], and 11-3-18 [IG(50) = 2.4 mg/liter]) yielded progeny showing a bimodal distribution, with an even number of sensitive and resistant progeny. This indicated the segregation of a single major gene for resistance in each cross, which was confirmed by the use of backcrosses, crosses between F(1) progeny, and control crosses between sensitive parents. However, there was also evidence of additional quantitative genetic components responsible for the increased IG(50)s of the more resistant isolates. A further cross was made between isolate PR11 and an F(1) progeny arising from isolate 11-3-18, and this also yielded progeny which were entirely prochloraz resistant. This suggested that resistance genes were allelic in these two isolates, with resistance conferred by a gene at the same locus (or closely linked loci), despite the fact that the isolates (PR11 and 11-3-18) originated from different continents. 相似文献
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Dyer C 《BMJ (Clinical research ed.)》2000,320(7234):535
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