Bidirectional selection for novel pheromone blend ratios in the almond moth, Cadra cautella.

The sex pheromone of the almond moth, Cadra cautella, is a blend of (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:Ac, the major component capable of inducing attraction alone) and (Z)-9-tetradecenyl acetate (Z9-14:Ac, the minor component, which is unattractive alone but augments attraction of the major component). In this study, the ratio of the two components responded to artificial directional selection in five of six selected lines, whereas no change was observed in the three control lines. The mean ratio (+/-SE) of Z9,E12-14:Ac to Z9-14:Ac went from 13.72 +/- 1.02:1 to 20.13 +/- 0.68:1 in high line 1, an increase of 47%. In the second high-selected line, the mean ratio (+/-SE) increased from 9.87 +/- 0.54:1 to 15.89 +/- 0.85:1, an increase of 61%. In low line 1, the mean ratio (+/-SE) in the parental generation was 10.74 +/- 0.78:1 and 7.35 +/- 0.41:1 in the last selected generation, a decrease of 32%. The response to selection was greater in low line 2, as the mean ratio (+/-SE) decreased from 10.11 +/- 0.66:1 to 5.65 +/- 0.55:1 in the last generation, a decrease of 44%. In low line 3, the mean ratio (+/-SE) in the parental generation was 13.63 +/- 0.82:1 and 6.47 +/- 0.26:1 in the last generation, a decrease of 53%. The response to selection was approximately symmetrical with a mean increase of 54% and a mean decrease of 43%. The increases in ratio observed in the high lines were caused by an increase in the titer of the Z9,E12-14:Ac component with no concurrent change in the titer of the component Z9-14:Ac. Among the low selected lines, the titers of both components increased; however, there was a greater relative increase in the titer of the component Z9-14:Ac. The absolute and relative titers of the sex pheromone components had decreased significantly in the F10 generation in some of the selected lines, five generations after the discontinuation of selection.