Carter, C., J.N. Sacalis. and T.J. Gianfagna

            Resistance to Colorado potato beetle in relation to zingiberene content of Lycopersicon species.


            Zingiberene, a sesquiterpene which occurs in Lycopersicon hirsutum.f. hirsutum (Snyder et al., 1987), was detected in the hirsutum Pl 126445 (hir) and confirmed by gas chromatography and mass spectroscopy. The occurrence of zingiberene in hir foliage extracts coincided with the sporadic appearance of resistance to Colorado potato beetle (Leptinotarsa decemlineata Say) (CPB) in hir. 2-Tridecanone, which has been associated

with resistance to CPB in L. hirsufum f. glabratum (Kennedy and Sorenson, 1985). was not present in hir but did occur in the glabratum Pl 134417 (gla), which lacked zingiberene. F2s of gla X hir segregated for the presence of zingiberene (X23:1 =3.57, p>=0.10; X215:1 =0.81, p>=0.50) and 2-tridecanone (X263:1 =0.44, p>=0.70). Survival of CPB larvae on foliage of the F2s declined in relation to estimated zingiberene content (r=-0.58, p<=0.001) and to 2-tridecanone content (r=-0.46, p<=0.01).

Zingiberene content of hir leaflets was estimated to be from 160-250 g per 2 cm2 leaflet. Crude extracts of hir and gla foliage were examined for toxicity to CPB larvae. CPB larval mortality increased in relation to estimated zingiberene contents of the hir extracts and in relation to 2-tridecanone contents of the gla extracts (Figure 1). We have purified zingiberene from roots of ginger (Zingiber officinale Roscoe) for further analyses of toxicity to CPB and quantification of zingiberene in hir.



For hir extracts, %M = 0 + 3.4 zingiberene (l), R2=0.79, p<=0.001).

For gla extracts, %M = 8 + 8.6 2-tridecanone (l), R20.78, p<0.001).


Literature cited:


Kennedy, G.G., and C.F. Sorenson. 1985. Role of glandular trichomes in the resistance of Lycopersicon hirsutum f. glabratum to Colorado potato beetle       (Coleoptera:Chrysomelidae).  J. Econ. Entomol. 78: 547-551.

Snyder, J.C., D.A. Johnson, D.E. Good and P.A. Weston. 1987. Type VI trichome exudates from chemotypes of L. hirsutum and L. hirsutum f.  glabratum. Tomato Genetics Cooperative Reports No. 37: 67-68.