Abstract
Plants are routinely subjected simultaneously to different abiotic and biotic stresses, such as heat, drought, and insect infestation. Plant-insect interactions in such complex stress situations are poorly understood. We evaluated the performance of the grain aphid (Sitobion avenae) in wheat (Triticum aestivum L.) exposed to a combination of heat and drought stresses. We also performed assays of the relative water content, nutritional quality, and responses of phytohormone signaling pathways. Lower relative water content and accumulation of soluble sugars and amino acids were observed in plants exposed to combined heat and drought stress. These conditions increased abscisic acid levels in the absence of aphids, as well as leading to higher levels of jasmonate-dependent transcripts. The grain aphid infestation further increased abscisic acid levels and the abundance of jasmonic acid- and salicylic acid-dependent defenses under the combined stress conditions. Aphids reared on plants grown under drought stress alone showed lower net reproductive rates, intrinsic rates of increase, and finite rates of increase compared with aphids reared on plants in the absence of stress. The heat-treated plants also showed a decreased aphid net reproductive rate. These findings demonstrate that exposure to a combination of stresses enhances plant defense responses against aphids as well as altering nutritional quality.
Highlights
In recent years, climate change and extreme weather events have become a key focus of increasing attention worldwide (Intergovernmental Panel on Climate Change, 2018).The frequency of heatwaves has increased in most parts of the world, and the resulting instability in precipitation has led to increases in the total arid surface area at high and intermediate latitudes (Li et al, 2014)
Our results indicated that drought significantly decreased the relative water content of wheat, but heat did not
Continuous drought stress resulted in a significant reduction in the foliar water content of host plants, which has a negative impact on sap feeder abundance (Huberty and Denno, 2004)
Summary
Climate change and extreme weather events have become a key focus of increasing attention worldwide (Intergovernmental Panel on Climate Change, 2018).The frequency of heatwaves has increased in most parts of the world, and the resulting instability in precipitation has led to increases in the total arid surface area at high and intermediate latitudes (Li et al, 2014). Previous studies have indicated that combined heat and drought cause an accumulation of sucrose that potentially protects mitochondria and other cellular components from the adverse effects of drought (Rizhsky et al, 2004) These combined stresses increase the accumulation of free amino acids, which are partially converted into proline to relieve abiotic stress (Cvikrova et al, 2013; Feller and Vaseva, 2014). Up-regulation of the SA and JA signaling pathways are two key plant defense responses induced by insect feeding (Koornneef and Pieterse, 2008).the combined effects of heat and drought might affect carbon and/or nitrogen in host plants through effects on the primary metabolism and the resistance of plants to herbivores (McDowell, 2011)
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