Identification of resistance to Bemisia tabaci Genn. in closely related wild relatives of cultivated tomato based on trichome type analysis and choice and no-choice assays

Abstract

The sweetpotato whitefly, Bemisia tabaci Genn., is a major pest of tomato (Solanum lycopersicum) and other crops throughout the tropics and subtropics. The objectives of this study were to characterize 255 accessions of S. galapagense, S. cheesmaniae and S. pimpinellifolium for trichome types, and to evaluate selected accessions with high densities of glandular trichomes for resistance to whitefly. Twenty-two accessions classified as either sparse or abundant for type IV trichomes were selected and evaluated for numbers of adults, eggs, nymphs, and puparium of whitefly in choice bioassays, for adult mortality and egg numbers in no-choice bioassays, and for densities of type I, IV, V, and VI trichomes. The highest whitefly resistance was detected in S. galapagense accessions VI063177 and VI037239 based on choice and no-choice bioassays. In addition, we found high levels of whitefly resistance in S. cheesmaniae accession VI037240 based on the choice bioassay and in S. pimpinellifolium accession VI030462 based on the no-choice bioassay. Whitefly resistance in VI037240 and VI030462 is noteworthy because these species are closely related to cultivated tomato and introgression of whitefly resistance should be relatively straightforward. High densities of type IV trichomes and low densities of type V trichomes were associated with reduced numbers of whitefly adults, nymphs, puparium, and eggs in the choice bioassay and with high adult whitefly mortality in the no-choice bioassay. Preliminary trichome analysis followed by choice and no-choice assays facilitated rapid identification of whitefly-resistant accessions from a large pool of candidates of different species.

Evaluation of wild tomato accessions (Solanum spp.) for resistance to two-spotted spider mite (Tetranychus urticae Koch) based on trichome type and acylsugar content

“…Ben-Israel et al (2009) found that spherical-shaped type VI trichomes accumulated higher concentrations of methylketone compared to lobe-shaped type VI trichomes in F 2 interspecific populations derived from S. habrochaites f. glabratum C. H. Müll. Similar associations were found between the presence of spherical-shaped type VI trichomes and whitefly resistance of VI030462 based on numbers of whitefly adults, nymphs, pupa, and eggs in the choice bioassay, and adult mortality and number of eggs from the no-choice bioassays (Rakha et al 2015), suggesting the presence of similar mechanisms of resistance to spider mite and whitefly in this accession. Besides high type IV trichome density, whitefly resistance has been associated with sparsity or absence of type V trichomes (Butter and Vir 1989;Firdaus et al 2012;Lucatti et al 2013;Rakha et al 2015).…”

“…Mean ± SE (n = 10) followed by different letters are significantly different according to according to least significant difference (LSD) test at p \ 0.05 habrochaites f. glabratum (PI 134417, PI 251304, PI 134418 and PI 126449), S. habrochaites (PI 127826, LA1777, LA 1740 and LA 2860) and S. pennellii (LA 716, LA 2963 and LA 2580) (Gentile et al 1969;Snyder and Carter 1984;Antonious and Snyder 2006;Saeidi and Mallik 2006;Onyambus et al 2011;Bleeker et al 2012;Lucini et al 2015). More than 250 wild tomato accessions were recently screened at AVRDC including S. galapagense, S. cheesmaniae and S. pimpinellifolium and high levels of whitefly (B. tabaci) resistance were identified in one or more accessions of each species (Rakha et al 2015). These species are closely related to cultivated tomato and introgression of resistance into cultivated tomato from these species should be easier and faster compared to the green-fruited species S. pennellii, and S. habrochaites (Rick, 1971;Peralta et al 2008).…”

“…In a previous work (Rakha et al 2015), these accessions were classified as abundant or sparse for type IV trichomes and evaluated for whitefly resistance based on number of adults, eggs, nymphs, and pupa from choice bioassays, and for adult mortality and egg number in no-choice bioassays (Rakha et al 2015). Ten of these accessions exhibited high whitefly resistance, except S. cheesmaniae VI037238.…”

“…and S. pimpinellifolium L. (formerly L. pimpinellifolium (L.) Mill.) (Firdaus et al 2012, Lucatti et al 2013, Rakha et al 2015, all of which can be easily crossed with S. lycopersicum (Rick 1971;Peralta et al 2008). Furthermore, S. pimpinellifolium accession TO-937 provided acceptable resistance to T. urticae (Fernández-Muñoz et al 2000).…”

“…Furthermore, S. pimpinellifolium accession TO-937 provided acceptable resistance to T. urticae (Fernández-Muñoz et al 2000). Eleven wild tomato accessions including S. cheesmaniae, S. galapagense, and S. pimpinellifolium were previously identified at AVRDC-The World Vegetable Center as resistant to B. tabaci (Rakha et al 2015). Identification of additional insect resistance in some or all these accessions would help to prioritize accessions for breeding cultivars with broad pest resistance.…”