Drought-Stressed Tomato Plants Trigger Bottom–Up Effects on the Invasive Tetranychus evansi

Abstract

Climate change will bring more drought periods that will have an impact on the irrigation practices of some crops like tomato, from standard water regime to deficit irrigation. This will promote changes in plant metabolism and alter their interactions with biotic stressors. We have tested if mild or moderate drought-stressed tomato plants (simulating deficit irrigation) have an effect on the biological traits of the invasive tomato red spider mite, Tetranychus evansi. Our data reveal that T evansi caused more leaf damage to drought-stressed tomato plants (≥1.5 fold for both drought scenarios). Mite performance was also enhanced, as revealed by significant increases of eggs laid (≥2 fold) at 4 days post infestation (dpi), and of mobile forms (≥2 fold and 1.5 fold for moderate and mild drought, respectively) at 10 dpi. The levels of several essential amino acids (histidine, isoleucine, leucine, tyrosine, valine) and free sugars in tomato leaves were significantly induced by drought in combination with mites. The non-essential amino acid proline was also strongly induced, stimulating mite feeding and egg laying when added to tomato leaf disks at levels equivalent to that estimated on drought-infested tomato plants at 10 dpi. Tomato plant defense proteins were also affected by drought and/or mite infestation, but T. evansi was capable of circumventing their potential adverse effects. Altogether, our data indicate that significant increases of available free sugars and essential amino acids, jointly with their phagostimulant effect, created a favorable environment for a better T. evansi performance on drought-stressed tomato leaves. Thus, drought-stressed tomato plants, even at mild levels, may be more prone to T evansi outbreaks in a climate change scenario, which might negatively affect tomato production on area-wide scales.

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…Drought-stressed tomato leaves showed an increase in the concentrations of total free amino acids and free sugars and a decrease of total protein, as already reported for tomato (Bauer et al, 1997;Ximénez-Embún et al, 2016). However, the effect of drought stress on nitrogen was not consistent, as it decreased in the assay performed with the TA strain but increased in the assay performed with the TNA strain.…”

“…Steady stress conditions were reached at about seven-nine days after ceasing irrigation. Both water stress regimes were above the wilting point associated with severe drought stress that was established at H = 16% for Moneymaker in our experimental conditions (Ximénez-Embún et al, 2016). The severity of drought stress was assessed by measuring the following parameters on the sub-terminal leaflet of the 4 th leaf: a) stomatal conductance (gs) using a leaf porometer (SC-1 Decagon-T, Pullman, USA); and b) variations in maximum quantum yield of photosystem II photochemistry (Fv/Fm), using a FluorPen FP 100 (PSI, Drasov, Czech Republic).…”

“…Nonetheless, the amino acid most clearly induced by drought stress was proline, which is not an essential nutrient. Proline has been shown to stimulate feeding in many different phytophagous arthropods (Showler, 2013;Ximénez-Embún et al, 2016). In addition, proline is unique among the amino acids because can be used by arthropods as a direct energy substrate for glycolysis and the production of ATP (Scaraffia and Wells, 2003).…”

“…Total protein content was determined according to the method of Bradford (1976). Hydrolytic enzymes (cathepsin B-, cathepsin L-, cathepsin D-and legumain-like) activities were assayed as described by Santamaria et al (2015a), and leucine aminopeptidase-and α-amylase-like activities and detoxification enzymes (esterase, glutathione S-transferase and P450) activities as described by Ximénez-Embún et al (2016). Reaction conditions are summarized in Table S3.3.…”

NO and H2O2 contribute to SO2 toxicity via Ca2+ signaling in Vicia faba guard cells

“…Esterase activity was measured as described by Ximénez-Embún et al (2016). After 3 h of SO 2 hydrate treatment, leaves (100 mg) were ground in 1 mL of 0.15 mol L −1 NaCl.…”