Fig. 2.

Cucumber varieties have different cucurbitacin levels in their tissues and Diabrotica balteata larvae sequester cucurbitacins from cucumber plants, mainly from the roots. (a-d) Cucurbitacins present in cucumber roots (a, n = 7–8), stems (b, n = 7–9), cotyledons (c, n = 7–8) or leaves (d, n = 7–8) of healthy plants (Undamaged: “Und.”) or after 15 second-instar D. balteata larvae freely fed on the plants (Damaged: “Dam.”) for five days. e Sequestered cucurbitacins in D. balteata larvae after freely feeding for five days on whole cucumber plants or only on roots or shoots (n = 5). Commercial varieties of cucumber were used for the experiments: “T” (Tanja), “S” (Sonja), “H” (Hokus) or “M76” (Marketmore 76). Bars indicate average (± SE). p values are given for treatments [generalized linear model (family, Gaussian)] followed by pairwise comparisons of least squares means (LSMeans). Not significant (n.s., p > 0.05). Different letters indicate significant differences among plant tissues within each cucumber variety, p < 0.05. Cucurbitacins present in plant and larvae are indicated with different colors and numbered 1–9 in the bars and in the legend: 1. Cuc IIa, 2. Dihydro-cuc B-glucoside, 3. Unknown cuc#1, 4. Cuc B-glucoside, 5. Cuc C, 6. Isomer of dihydro-cuc B-glucoside, 7. Metabolized cuc #1, 8. Deacetylated-dihydro-cuc B-glucoside, 9. Unknown cuc#2