Resistencia do acesso la 1777 de lycopersicon hirsutum f. typicum a tuta absuluta (Meyrick) (Lepidoptera : Gelechiidae)

Abstract

The study was carried out in green house with the objective of evaluating the resistance of the access LA 1777 of Lycopersicon hirsutum f. typicum to Tuta absoluta, of selecting plants of this access that demonstrate resistance and of beginning studies on the chemical causes of this resistance. Two experiments were carried out, one during the summer and another during the winter season. The characteristics assessed were: number and size of the mines; duration and larval mortality; duration, mortality, weight and sexual proportion of pupas and the reproductive characteristics of T. absoluta (pre-oviposition and oviposition period, number of eggs/female and rate of eggs appearance). Gas chromatography couple to masses spectrometer (CG-MS) was used to preliminarily identify substances in the hexanic extract of leaves of the access LA 1777 of L. hirsutum f.Typicum that may be related to the resistance. The results of the biological characteristics of T. absoluta were submitted to analysis of variance and to the Scott-Knott multiple range test at 5% probability. The mean and standard error were calculated. Regression analysis (p < 0.05) between the biological characteristics of T. absoluta and total ions current (TIC) were made. The composition of the hexanic extract was identified through comparison of the obtained mass spectra and the mass spectra of substance available in the “John Wiley” library with 160,000 compounds. The presence of larger number of small mines in the access LA 1777 indicated antixenose as resistance mechanism; and longer larval phase; high larval mortality and change of the reproductive characteristics of T. absoluta indicated antibiose as resistance mechanism. Fourteen peacks were observed in the chromatograms of leaves from the resistant plants with retention times varying up 10.49 to 26.03 minutes. High correlations between total units of peack areas and biological characteristics of the moth were observed, which suggests the involvement of more than one chemical pound in this resistance. The probable substances involved in this resistance were sesquiterpenes as: farnesene or ; α-bergamotene fr the peack one, α-humulene or б-elemene, for the peack three; the 2,5,5 trimetyl 1,3,6 heptatriene, ou (+) camphene, or farnesene or santalol for the peack eight and α-bergamotene or β-sinesal ou farnesene or farnesol in the peack nine of cromatograms.