Effect of cropping season and possible compounds involved in the resistance of Lycopersicon hirsutum f. typicum to Tuta absoluta (Meyrick) (Lep., Gelechiidae)

The effect of cropping season on the resistance of the accession LA 1777 of Lycopersicon hirsutum f. typicum to the tomato leafminer Tuta absoluta (Me yrick) and the preliminary identification of the possible compounds involve d in this trait were the objectives of this study. Two experiments were car ried out with the accession LA1777 and the commercial cultivar Santa Clara of Lycopersicon esculentum. The first experiment was carried out during the summer season (January to April 1997) and the second was carried out durin g the autumn-winter season (May to September 1997). The accession LA 1777 w as significantly more resistant to T. absoluta than the commercial cultivar , especially during the autumn-winter cropping season. Either antibiosis or antixenosis was probably responsible for the higher larvae mortality (54.2 and 91.2% for the summer and autumn-winter seasons, respectively) and long er larval development of T. absoluta (14.2 and 25.9 days for summer and aut umn-winter seasons, respectively) on L. hirsutum f. typicum as compared wit h L. esculentum (11.0 and 19.6 days for summer and autumn-winter seasons, r espectively). Insect fecundity parameters such as oviposition period, numbe r of eggs/female, and rate of larvae eclosion were also negatively affected by L. hirsutum f. typicum. Fourteen main peaks were observed in total ion chromatograms of both tomato species. Eleven of these were present only in chromatograms of the accession, one was only present in chromatograms of th e commercial cultivar, and two peaks were present in chromatograms from bot h when hexane extracts of leaves were subjected to a gas chromatographic-ma ss spectrometric analysis (GC-MS). However, the matches obtained between th e peak spectra and the MS database were too low to justify even preliminary identification of the compounds.