Effects of continuous versus pulsed drought on mycorrhiza-crop-aphid interactions

全球变化情景预测，随着气温的上升，可用水将更加稀缺，从而导致更长的旱期。水分供应的不平衡调节了植物资源分配的变化，并导致各种生理反应，如气孔关闭和光合作用速率受到抑制。这些反应影响植物代谢物的生物合成，从而对食草动物和病原体产生影响，这取决于植物的质量。例如，植物胁迫假说预测，在干旱胁迫下的植物上，蚜虫表现得更好。此外，大多数植物都与共生真菌共生，形成丛枝菌根(AM)，除了其他作用外，它还可以缓解植物的干旱胁迫。虽然许多研究已经研究了持续干旱胁迫对植物生长、生理和化学的影响，但脉冲干旱胁迫事件要现实得多。此外，干旱和AM对麦长管蚜的综合影响被忽略。因此，在这项建议中，将研究不同干旱制度(脉冲干旱胁迫与持续干旱胁迫与井水灌溉)在AM存在或不存在的情况下对作物小麦及其主要害虫的形态、生理或化学反应的影响。将监测干旱状况和AM状态对植物生长特性的影响以及水合状态的相对变化。将棉铃虫饲养在不同处理和不同表现性状的植物上，并测量种群增长，以检验植物胁迫、脉冲胁迫和植物活力假说。同时，将使用代谢组学方法分析韧皮部渗出物的化学成分。多变量统计将使我们能够预测特定的韧皮部代谢物对蚜虫的作用。随后，将使用人工饲料测试碳水化合物、氨基酸和特定次生代谢物的比例的作用。将选择不同植物处理韧皮部浓度不同的代谢物。了解预期气候变化情景下菌根-作物-蚜虫的相互作用可能有助于制定改进的种植策略，并建立具有高耐旱性和高抗虫性的品种。此外，对脉冲干旱胁迫对蚜虫种群增长影响的潜在机制的了解可能有助于预测疫情的发生。

Global change scenarios predict scarcer water availability together with increasing temperatures, leading to longer drought periods. Imbalances in water supply mediate changes in resource allocation of plants and cause various physiological responses, such as closure of stomata and suppressed photosynthetic rates. These responses affect the biosynthesis of plant metabolites, which has consequences on herbivores and pathogens that depend on the plant quality. For example, the plant stress hypothesis predicts that aphids perform better on drought-stressed plants. Furthermore, most plants are associated with symbiotic fungi, forming an arbuscular mycorrhiza (AM), which can, amongst other effects, alleviate drought stress of plants. While many studies have investigated the effects of continuous drought stress on plant growth, physiology and chemistry, pulsed drought stress events are much more realistic. Moreover, the combined effects of drought and AM on aphids have been neglected. Therefore, in this proposal the effects of different drought regimes (pulsed drought stress versus continuous stress versus well-irrigated) on morphological, physiological or chemical responses of the crop plant wheat and their main aphid pest will be studied in presence or absence of AM. Effects of drought regime and AM status on plant growth traits and relative changes in hydration status will be monitored. Aphids will be reared on plants of the different treatments and various performance traits and the population growth measured to test the plant stress, pulsed stress and plant vigour hypotheses. In parallel, the chemical composition of phloem exudates will be analysed using metabolomics approaches. Multivariate statistics will allow us to make predictions about the role of specific phloem metabolomes for aphids. Subsequently, the role of the ratio of carbohydrates to amino acids to specific secondary metabolites will be tested using artificial diets. Metabolites will be selected that differ in concentration between the phloem of the plant treatments. Understanding the mycorrhiza-crop-aphid interactions under expected climate change scenarios may help to develop improved planting strategies and to establish cultivars with a high drought tolerance and high aphid resistance. Furthermore, the knowledge about the mechanisms underlying effects of pulsed drought stress on aphid population growth may allow for prediction of outbreaks.