Abstract
In Brazil, the tomato is cultivated in almost all geographic regions even though its yield is significantly reduced by pests and diseases. Among these pests and diseases, whitefly is a major problem that causes direct and indirect damage due to its role in transmission of geminiviruses. The aim of the present study was to compare the degree of resistance to the silverleaf whitefly of tomato plant lines rich in acyl sugars (AS), zingiberene (ZGB), and 2-tridecanone (2-TD) and to establish whether selection for strains with higher densities of glandular trichomes promotes sufficient resistance to this insect pest. The investigated lines were developed by performing back-crossings in tomato (Solanum lycopersicum) from the interspecific crossing of S. lycopersicum x S. habrochaites var. glabratum 'PI 134417'. Lines rich in AS, ZGB, and 2-TD were tested for their levels of resistance to B. tabaci biotype B. Two tomato plant lines (TOM-584 and TOM-679) with normal AS levels and one wild specimen (PI 134417) with high 2-TD content were used as controls. TOM-687, ZGB-703, and TOM-622 were less preferred by B. tabaci for oviposition, and nymphs exhibited a poorer survival rate on those plant lines than on the susceptible controls, TOM-584 and TOM-679. Allelochemical-rich lines exhibited pest resistance, whereas the controls did not, and the allelochemical-rich lines did not differ significantly from each other in the level of resistance. The results show that the development of tomato plant lines rich in 2-TD, ZGB and AS is an effective option for indirect selection for resistance to B. tabaci biotype B. All lines selected based on high trichome density except for BPX-365F-751-05-01-03 exhibited fewer nymphs than the susceptible controls, indicating that selection for more glandular trichomes was generally effective in promoting increased resistance to the silverleaf white flay.
Highlights
From the nine genotypes that were selected for trichome density, seven (BPX-365F-751-05-01-03, BPX-365F-751-05-02-02, BPX-365F-751-10-01-01, BPX365F-751-10-01-02, BPX-365F-899-07-04-02, BPX-365F899-14-02-03, and BPX-365F-899-14-02-04) corresponded to F7 lines obtained from the crossing of TOM-679 and TOM-600
Oviposition by adults and number nymphs of B. tabaci biotype B were affected by the presence of the allelochemicals 2-TD, ZGB, and acyl sugars (AS) in the assessed tomato plant genotypes (Table 1)
This indicates that this genotype, whose leaflets are rich in methyl-ketones (2-TD in particular), allelochemicals might not be the only factor contributing to resistance to this pest
Summary
In Brazil, the tomato (Solanum lycopersicum L., syn. Lycopersicon esculentum Mill.) crop is cultivated in virtually every geographic area and is one of the most important crops. The silverleaf whitefly, Bemisia tabaci (GENNADIUS, 1889) biotype B (Hemiptera: Aleyrodidae) (= Bemisia argentifolii), is commonly present in plantations, where it causes direct (yield reduction) and indirect damage due to the transmission of geminiviruses. This pest is usually managed by applying insecticides, Ciênc. Some wild tomato specimens have exhibited satisfactory levels of resistance to insect pests due to the presence of allelochemicals, such as the sesquiterpenes [mainly zingiberene (ZGB)], acyl sugars (AS), and 2-tridecanone (2-TD), in specimens ‘PI-127826’ of S. habrochaites S. Spooner (=Lycopersicon hirsutum), ‘LA-716’ of S. pennellii Correl (=L. pennellii), and ‘PI 134417’ of S. habrochaites, respectively (CARTER; SACALIS; GIANFAGNA, 1988; FREITAS et al, 2002; TOSCANO; BOIÇA JÚNIOR; MARUYAMA, 2002)
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