Station d'Amelioration des Plantes Maraicheres, Domaine Saint-Maurice, 84140 Montfavet, FRANCE
The accession LA 1401 of the wild tomato L. cheesmanii was studied for determining the origin of its resistance to Liriomyza trifolii (Burgess) (1). Observations were already reported in previous paper (2). The cultivar Flora Dade was used as a susceptible control.
A screening test was developed to control the antibiosis activity of leaves crude extracts from these two tomato plants and the different fractions obtained after column chromatography of the extract. The procedure was as following. A crude chloroform extract was sprayed on the two leaves of seven days old bean plants. The leaf surface of tomato plant extracted was equivalent to the leaf surface of the bean plant sprayed. Thus, 20 mg of crude extract was being deposited on about 360 cm^2^ of bean leaves, corresponding to six leaves on three plants. The three plants treated were placed in test cage in an insectarium at 25 deg. C and exposed for 24 hours to 30 females of L. trifolii. Four days later, the total number of mines was recorded. One test consisted of three groups of three bean plants, one treated with the extract from L. cheesmanii, another one with the extract from Flora Dade and the last one sprayed only with chloroform. Four replications were effected.
This test showed an important anti-feedant activity of the crude chloroform extract from L. cheesmanii compared with the control Flora Dade: about 90% fewer mines on the bean plants treated with L. cheesmanii extract. Among the different extract fractions tested, only one showed an anti-feedant activity. After purification and identification by mass spectrometry and N.M.R., this fraction showed to contain a family of compounds, the sucrose esters, which the general formula is (2,3,4-tri-O-acyl)-a-D-glucopyranosyl)-(3-O-acyl)-b-D-fructofuranoside, where the acyl groups are fatty acids from C2 to C24:1. They are associated with the glandular trichomes on the leaves. Sucrose esters have already been described in others Solanaceae and wild Lycopersicon species (3) but their general formula are slightly different. Moreover, no antibiosis activity was reported.
References:
(1) Jouy, N. 1990. "Etude de la resistance naturelle de deux Lycopersicon a des ravageurs de cultures maraicheres. Identification des substances responsables: les (2,3,4-tri-O-acyl)-a-D-glucopyranosyl)-(3-O-acyl)-b-D-fructofuranoside." These de Doctorat, Universite des sciences et techniques du Languedoc.
(2) Latterot, H., D. Bordat, M. Renand and A. Moretti 1987. TGC 37
(3) King, R.K., L.A. Calhoun, R.P. Singh and A. Boucher 1990. Phytochemistry, 29, (7), p 2115