The role of primary and secondary metabolites in chrysanthemum resistance toFrankliniella occidentalis.

The presence of deleterious secondary metabolites to western flower thrips (WFT) (Frankliniella occidentalis Pergande) in several chrysanthemum (Dendranthema grandiflora Tzvelev) cultivars was tested. WFT performance on leaf sap mixed with artificial diet was compared to WFT performance on a control of artificial diet mixed with water. Leaf sap of six of 10 chrysanthemum cultivars tested had a significant negative effect on WFT performance and therefore contained deleterious secondary metabolites. Leaf sap of a resistant and a susceptible chrysanthemum cultivar were fractionated by gel to study the role of secondary metabolites in greater detail. None of the 20 individual fractions obtained had a negative effect on WFT performance, whereas after mixing of these fractions activity was found again. Moreover, WFT performance on the fraction mixture of the resistant cultivar was significantly lower than on the susceptible fraction mixture. The results suggest that WFT resistance in the cultivars studied was caused by several secondary metabolites that had an additional or synergistic negative effect on WFT performance. The role of a deficiency of primary metabolites in WFT resistance of chrysanthemum was also investigated. WFT performance on leaf sap with and without extra primary metabolites (artificial diet) was compared. The variance in WFT performance was significantly smaller when extra primary metabolites were added; WFT performance on leaf sap with and without extra primary metabolites was not correlated. The results suggest that resistance was partly caused by a deficiency of primary metabolites.