Clonal selection for yield in pyrethrum,Chrysanthemum cinerariaefolium Vis.

Summary Pyrethrum is grown for the insecticides found in the flowers. Due to its perennial habit each selection stage should last three years. Most traits can be adequately observed or measured within one-year cycles. However, it has not previously been investigated whether flower yield, one of the most important traits, could be adequately assessed in one year.Seven replicated yield trials, comprising 110 clones in a similar stage of selection, were observed over a period of three years. The clone effect on flower yield, pyrethrins yield and pyrethrins content were very significant in all trials. The correlation coefficients between the first year's results and the total results averaged +0.91 for flower yield and +0.93 for pyrethrins content. Selection of the highest yielding clones comprising one third of the total number resulted in an increase in pyrethrins yield of 34.3% when selected after the first year and in an increase of 37.5% when selected after three years. This increase was predominantly due to an increase in flower yield, which is caused by the much greater variation for flower yield than for pyrethrins content together with an inverse relation between these two traits.It is therefore possible to select in one-year stages with only a final testing over a 2 to 3 year period.