Abstract
Climate change is expected to increase drought periods and the performance and dispersal of some invasive species such as Tetranychus evansi, which has been reported to take advantage of the nutritional changes induced by water-shortage on the tomato cultivar Moneymaker (MM). We have examined the implications for mite’s biology of four accessions of the drought-adapted tomatoes, “Tomàtiga de Ramellet” (TR), under moderate drought stress. Mite performance was enhanced by drought in two accessions (TR61 and TR154), but not in the other two accessions (TR58 and TR126). We selected one accession of each outcome (i.e., TR154 and TR126) to further analyze plant nutritional parameters. We found that free sugars and most essential amino acids for mites were induced by drought and/or mite infestation on MM and TR154 plants, whereas sugars were not altered and a reduced number of essential amino acids were induced by drought in TR126. Remarkably, mite performance was enhanced by leaf infiltration of free sugars, essential amino acids mixture, and L-proline on well-watered MM and by free sugars on drought-stressed TR126 plants. These results indicate a positive link between the induction of soluble carbohydrates and amino acids used by the plant for osmotic adjustment and mite performance. The effects of drought and/or mite infestation on the defense response of plants was analyzed at three levels: phytohormone accumulation, the transcript levels of marker genes linked to jasmonates (JAs), salicylic acid (SA), and abscisic acid (ABA) pathways, and the activity of defense proteins. The ability of T. evansi to downregulate the accumulation of defense-related phytohormones was noted on MM and the two TR accessions analyzed (TR126 and TR154), though differences in the induction of protein defense genes and activities by drought and/or mite infestation were observed among them. These results emphasize the importance of studying plant biotic and abiotic stress factors in combination and provides an experimental framework for screening drought-tolerant tomato accessions that will be also resistant to herbivore mites.
Highlights
Tomato (Solanum lycopersicum L.) is a major vegetable crop grown all over the world in outdoor fields and greenhouses
The effect of drought stress on stomatal conductance, photosynthetic efficiency, and stem length observed in Experiment 1 (Supplementary Figure S1 and Supplementary Table S3) and Experiment 2 (Supplementary Figure S2 and Supplementary Table S4) indicates that the severity of drought stress attained under our experimental conditions can be considered as moderate
Our data reveal that drought stress has a differential effect on the performance of T. evansi in drought-adapted “Tomàtiga de Ramellet” tomatoes
Summary
Tomato (Solanum lycopersicum L.) is a major vegetable crop grown all over the world in outdoor fields and greenhouses. Tomato plants are exposed to a combination of biotic and abiotic stresses, soil water deficiency, and arthropod pests being among the most critical. Water shortage caused by drought periods can have important consequences for tomato production, as it might produce yield reduction of up to a 50% in the case of an equivalent reduction in irrigation (Cantore et al, 2016). Tomato plants are attacked by a number of insect and mite pests which significantly reduce fruit yield and quality. Losses due to these pests are estimated to be about 34.4% of attainable tomato yield under current production practices (Zalom, 2003). The sustainability of tomato production is threatened by an increasing number of invasive arthropod pests (Navajas et al, 2013; Tonnang et al, 2015)
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