Table_1_Phosphorus availability drives mycorrhiza induced resistance in tomato.xlsx

Arbuscular mycorrhizal (AM) symbiosis can provide multiple benefits to the host plant, including improved nutrition and protection against biotic stress. Mycorrhiza induced resistance (MIR) against pathogens and insect herbivores has been reported in different plant systems, but nutrient availability may influence the outcome of the interaction. Phosphorus (P) is a key nutrient for plants and insects, but also a regulatory factor for AM establishment and functioning. However, little is known about how AM symbiosis and P interact to regulate plant resistance to pests. Here, using the tomato-Funneliformis mosseae mycorrhizal system, we analyzed the effect of moderate differences in P fertilization on plant and pest performance, and on MIR against biotic stressors including the fungal pathogen Botrytis cinerea and the insect herbivore Spodoperta exigua. P fertilization impacted plant nutritional value, plant defenses, disease development and caterpillar survival, but these effects were modulated by the mycorrhizal status of the plant. Enhanced resistance of F. mosseae-inoculated plants against B. cinerea and S. exigua depended on P availability, as no protection was observed under the most P-limiting conditions. MIR was not directly explained by changes in the plant nutritional status nor to basal differences in defense-related phytohormones. Analysis of early plant defense responses to the damage associated molecules oligogalacturonides showed primed transcriptional activation of plant defenses occurring at intermediate P levels, but not under severe P limitation. The results show that P influences mycorrhizal priming of plant defenses and the resulting induced-resistance is dependent on P availability, and suggest that mycorrhiza fine-tunes the plant growth vs defense prioritization depending on P availability. Our results highlight how MIR is context dependent, thus unravel molecular mechanism based on plant defence in will contribute to improve the efficacy of mycorrhizal inoculants in crop protection.

丛枝菌根（Arbuscular mycorrhizal，AM）共生关系能够为宿主植物带来诸多益处，包括营养提升及抵御生物胁迫的防护。在多种植物系统中，已报道丛枝菌根诱导的抗性（Mycorrhiza Induced Resistance，MIR）能够抵御病原体和食草昆虫，然而营养的可获得性可能会影响这种互作的结果。磷（Phosphorus，P）对植物和昆虫而言均为关键营养素，同时也是丛枝菌根建立与功能发挥的调控因子。然而，关于丛枝菌根共生与磷如何相互作用以调节植物对害虫的抵抗力的了解尚显不足。在本研究中，我们利用番茄与Funneliformis mosseae丛枝菌根系统，分析了中等磷肥施用量差异对植物和害虫表现、以及对生物胁迫因子（包括真菌病原菌Botrytis cinerea和食草昆虫Spodoperta exigua）的MIR的影响。磷肥施用量对植物的营养价值、植物防御机制、病害发生及幼虫存活率产生影响，但这些效应受到植物丛枝菌根状态的影响。接种F. mosseae的植物对B. cinerea和S. exigua的增强抵抗力依赖于磷的可获得性，因为在最限制磷的条件下并未观察到保护作用。MIR并非直接由植物营养状态的改变或与防御相关的植物激素的基线差异所解释。对植物早期防御反应的分析，特别是对与损伤相关的低聚半乳糖醛酸酯类分子的反应，表明在中等磷水平下发生了植物防御的转录激活，而在严重磷限制条件下则没有。结果表明，磷影响丛枝菌根对植物防御的启动，由此产生的诱导抗性依赖于磷的可获得性，并暗示丛枝菌根根据磷的可获得性精细调节植物生长与防御的优先级。我们的研究结果突显了MIR的情境依赖性，并基于植物防御机制的分子机制研究，将有助于提高丛枝菌根接种剂在作物保护中的功效。