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

Abstract

Tomato wild relatives are important sources of resistance to many pests of cultivated tomato [Solanum lycopersicum L. (syn. Lycopersicon esculentum Mill.)]. Eleven wild tomato accessions previously identified at AVRDC-The World Vegetable Center as resistant to Bemisia tabaci were evaluated for resistance to the two-spotted spider mite [Tetranychus urticae (Koch.)] based on egg numbers using the leaf disc and Tanglefoot no-choice bioassays, and damage scores in choice bioassays. Highest resistance based on choice and no-choice bioassays was identified in AVRDC S. galapagense accessions VI057400, VI045262, VI037869 and VI037239, and S. cheesmaniae accession VI037240, all of which are new sources of T. urticae resistance. In addition, S. pimpinellifolium accession VI030462 exhibited resistance only in the no-choice bioassay based on egg numbers. Resistance to T. urticae based on the number of eggs from the no-choice bioassays was positively correlated with density of type IV glandular trichomes and negatively correlated with densities of type V trichomes. All resistant accessions accumulated high levels of total acylsugars, which were positively associated with type IV trichomes. There was a significant negative relationship between acylsugar content and T. urticae egg numbers from the no-choice bioassays. There was high correlation between the results from the leaf disc test and the Tanglefoot nochoice bioassay. These findings support the possible presence of broad-based insect and mite resistance in accessions closely related to cultivated tomato.

QTL mapping of insect resistance components of Solanum galapagense

“…This indicates that, although the same QTL is found to affect adult survival of both whitefly species, there may be more experimental noise in the survival data of T. vaporariorum . A possible cause for this additional noise may be that T. vaporariorum is stronger than B. tabaci, making it occasionally possible for T. vaporariorum to escape from the leaf even though it was “glued” by the sticky content of the type IV trichomes (Rakha et al 2017a; Vosman et al 2018). Alternatively, some compounds related to the resistance may have a more detrimental effect on B. tabaci than on T. vaporariorum .…”

“…Leaf trichomes were shown to play a critical role in the interaction with pests. Several lines of evidence show that the glandular trichome type IV is particularly important in resistance against insects (Firdaus et al 2012; Muigai et al 2003; Rakha et al 2017a, c; Simmons et al 2005). Trichome type IV occurs on some accessions of tomato wild relatives, including S. pennellii , S. habrochaites , S. galapagense and S. pimpinellifolium.…”

Screening recently identified whitefly/spider mite‐resistant wild tomato accessions for resistance to Tuta absoluta

“…Solanum galapagense also was resistant to whitefly and spider mite (Rakha et al., , ), and tomato fruitworm ( Helicoverpa armigera Hübner) tested in Taiwan at WorldVeg headquarters (Asif et al. unpublished data), indicating that resistance in this accession extends to multiple insects—a valuable finding.…”

“…In 2012, the insect was first reported in sub-Saharan Africa and subsequently spread into Tanzania, Uganda and Kenya, where it has become a serious pest of field and greenhouse tomato production (Tonnang et al, 2015). Previous WorldVeg studies found glandular trichome-based resistance to whitefly and spider mite in certain accessions of S. cheesmaniae, S. galapagense and S. pimpinellifolium (Rakha et al, 2017a(Rakha et al, , 2017b, and the present study aimed to evaluate these seven accessions for resistance to T. absoluta in choice and no-choice feeding bioassays.…”

“…(Rakha, Hanson, & Ramasamy, 2017a, Rakha, Bouba, Ramasamy, Regnard, & Hanson, 2017b. Resistance in these accessions was highly correlated with high densities of type IV trichomes and absence or low densities of type V trichomes (Rakha et al, 2017b), and is based on acyl sugars and/or sesquiterpenes (unpublished data), metabolites associated with insect resistance (Lin, Trumble, & Kumamoto, 1987;Liedl et al, 1995;Mutschler et al, 1996;Fancelli, Vendramim, Frighetto, & Lourencao, 2005;McDowell et al, 2011). It is possible that some of these accessions offer broad-spectrum insect resistance, including to T. absoluta.…”