Phytohormone content variation manipulated by Bemisia tabaci participated in inhibiting tobacco growth: Gibberellin may play a crucial role

ABSTRACT Infestation of Bemisia tabaci MEAM1 (Gennadius) causes significant phenotypic changes in a variety of plants. However, plants damaged by Trialeurodes vaporariorum (Westwood) show no similar changes. In this study, to explore the effects of MEAM1 infestation on tobacco growth and the mechanism underlying these effects, growth index, and photosynthesis of infested tobacco (Nicotiana tabacum L.), as well as content of hormones, including auxin, gibberellin, cytokinin, abscisic acid, methyl jasmonate, and ethylene were measured. The results demonstrated that infestation of MEAM1 significantly inhibited tobacco growth and the inhibition effect varied with MEAM1 feeding densities, 50 MEAM1 per infested tobacco plant decreased plant height, internode length, and dry weight cm-2, and this inhibition peaked at 200 MEAM1 per plant, which reduced by 52.17%, 43.83%, and 45.61% that of controls, respectively. Additionally, MEAM1 infestation inhibited photosynthesis of tobacco, causing significant decrease in chlorophyll content, photosynthetic rate and stomatal conductance. However, the effects of T. vaporariorum infestation on tobacco were significantly lighter than that of MEAM1. Hormones assays indicated that infestation with 200 MEAM1 per plant for 30 d significantly affected hormones content, among which gibberellin content was specifically reduced compared with that of uninfested control plants and T. vaporariorum infested plants. Furthermore, exogenous application of 1 and 2 μM gibberellin alleviated the reduction in plant height mediated by MEAM1. Therefore, infestation of MEAM1 significantly inhibited tobacco growth and photosynthesis, and the reduction of gibberellin content may contribute to this inhibition.