Variation of 2-Tridecanone level in tomato plant leaflets and resistance to two mite species (Tetranychus sp.)

The wild tomato accession Lycopersicon hirsutum f. glabratum ‘PI 134417’ is a promising source of resistance to arthropods in tomato. It is self compatible and intercrosses easily with the cultivated species Lycopersicon esculentum. It is resistant to several arthropods, including spider mites, and these resistances have been related to the presence of high contents of 2-tridecanone (2-TD) and other methyl ketones in the leaves. The objective of this study was to evaluate the contribution of 2-TD concentration in the leaflets of Lycopersicon for resistance to the spider mites Tetranychus urticae (Koch, 1836) and T. ludeni Zacher, 1913. Plants of two segregating generations (F₂) were evaluated through the thumbtack bioassay (Weston & Snyder, 1990) in two different assays. Both experiments included as checks L. esculentum ‘TSWV-547’ (mite susceptible), L. hirsutum f. glabratum ‘PI 134417’ (resistant) and the interspecific hybrid F₁ (TSWV-547 × PI 134417). In the first experiment, 10 genotypes selected from F₂ (TSWV-547 × PI 134417), with contrasting 2-TD concentrations in the leaflets, were tested for resistance to T. urticae. In a second experiment, seven genotypes of the F₂ (TSWV-547 × BPX-318p1#230), also with contrasting 2-TD concentrations, were used to evaluate the resistance to T. ludeni. BPX-318p1#230 is a single plant selected from the segregating population F₂ (TSWV-547 × PI 134417) for its high 2-TD content. In both experiments, high negative correlations (r = − 0.88; − 0.91 and − 0.93 in the first experiment, and r = − 0.78, − 0.99 and − 0.96 in the second experiment) were found between the 2-TD content and average distance travelled by the spider mites after 60, 90 and 120 minutes, respectively. The level of resistance (repellency) to spider mites T. urticae and T. ludeni in the genus Lycopersicon appears to be mediated by the 2-TD levels present in the tomato leaflets. The similar results of both experiments showed that selection for high 2-TD content in leaflets can lead to genetic improvement in the direction of increased levels of spider mite resistance in tomato. This revised version was published online in August 2006 with corrections to the Cover Date.