A preliminary investigation had been made into the evolution of copper tolerance in some Californian populations of Mimulus guttatus growing on abandoned copper mines. It has been shown that populations growing on soil with normally toxic levels of copper were tolerant to this heavy metal. There was also some indication of an increase in tolerance to zinc, lead and nickel in the copper tolerant populations, even when the soil was not particularly rich in these other metals. With one exception, populations on non-contaminated soils were non-tolerant as judged by root growth in aqueous solutions or soil containing copper. Furthermore, there was a marked difference in germination and seedling establishment on copper soil between stocks originating from mine and from non-mine environments. The superiority of the mine populations under such circumstances was less marked when established plants were potted up in mine soil. By testing the F 1 progeny of crosses involving tolerant and non-tolerant parents it was found that copper tolerance is dominant in effect at low copper concentrations, intermediate at intermediate concentrations, and recessive in effect at high copper concentrations. When the plants had been grown on normal soil there appeared to be a requirement for copper at low concentrations among the offspring of tolerant parents. It is suggested that this may result from the mechanism of tolerance by complexing the copper and thus making it unavailable to the plant. The genetic control of zinc and lead tolerance is not clear, but there is evidence that zinc tolerance may be dominant at concentrations of zinc in solution of 15 parts/10 6 .

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Bioassay-directed fractionation of extracts of chrysanthemum leaves using a choice test permitted isolation of a fraction that exhibited repellent activity against the western flower thrips (WFT). Analysis of this fraction from cultivars exhibiting varying degrees of host-plant resistance to WFT by high performance liquid chromatography revealed a distinctive peak, the height of which correlated with the degree of resistance of those cultivars to WFT. The peak was attributed to a novel unsaturated isobutylamide, N-isobutyl-(E, E, E, Z)-2,4,10,1 2-tetradecatetraen-8-ynamide.

The western flower thrips, Frankliniella occidentalis (Pergande), occurs from sea level to subalpine altitudes in western North America (Bryan and Smith 1956). Until recently, it was assumed that this species was found primarily west of the Rocky Mountains and that Frankliniella tritici (Fitch), the eastern flower thrips, was the dominant flower thrips in both eastern Canada and United States. Beshear (1983) reported F. occidentalis on cotton, peas, beans, and peanuts in Georgia. The following year, in the Niagara Peninsula of Ontario, the tomato spotted wilt virus caused extensive crop losses to greenhousegrown tomatoes and ornamentals. The virus-vector was identified as F. occidentalis (Allen and Broadbent 1986). Previously, F. fusca was the only known vector of tomato spotted wilt virus in Ontario and the eastern provinces (Paliwal 1974, 1976).