Table_6_Arbuscular mycorrhizal fungus changes alfalfa response to pathogen infection activated by pea aphid infestation.XLSX

IntroductionArbuscular mycorrhizal (AM) fungi are important for the resistance of plants to insect infestation and diseases. However, the effect of AM fungal colonization of plants response to pathogen infection activated by pea aphid infestation is unknown. Pea aphid (Acyrthosiphon pisum) and the fungal pathogen Phoma medicaginis severely limit alfalfa production worldwide.
MethodsThis study established an alfalfa (Medicago sativa)–AM fungus (Rhizophagus intraradices)–pea aphid–P. medicaginis experimental system to clarify the effects of an AM fungus on the host plant response to insect infestation and subsequent fungal pathogen infection.
ResultsPea aphid increased the disease incidence of P. medicaginis by 24.94%. The AM fungus decreased the disease index by 22.37% and enhanced alfalfa growth by increasing the uptake of total nitrogen and total phosphorus. The aphid induced polyphenol oxidase activity of alfalfa, and the AM fungus enhanced plant-defense enzyme activity against aphid infestation and subsequent P. medicaginis infection. In addition, the AM fungus increased the contents of jasmonic acid and abscisic acid in plants exposed to aphid infestation or pathogen infection. Abscisic acid and genes associated with the gene ontology term “hormone binding” were upregulated in aphid-infested or pathogen-infected alfalfa.
DiscussionThe results demonstrate that an AM fungus enhances plant defense and signaling components induced by aphid infestation, which may contribute to improved defense against subsequent pathogen infection.

引言：丛枝菌根（Arbuscular Mycorrhizal, AM）真菌对植物抵御昆虫侵袭与病害具有重要作用。然而，丛枝菌根真菌定殖植物后，其对植物响应豌豆蚜（Acyrthosiphon pisum）侵袭所激活的病原菌侵染的影响尚不明确。豌豆蚜与真菌病原菌苜蓿茎点霉（Phoma medicaginis）在全球范围内严重制约苜蓿的生产。
方法：本研究构建了苜蓿（Medicago sativa）-根内根囊霉（Rhizophagus intraradices）-豌豆蚜-苜蓿茎点霉的实验体系，以明确丛枝菌根真菌对宿主植物响应昆虫侵袭及后续真菌病原菌侵染的调控效应。
结果：豌豆蚜使苜蓿茎点霉的病害发病率提升24.94%。丛枝菌根真菌可使病害指数降低22.37%，并通过提高植株对总氮与总磷的吸收促进苜蓿生长。豌豆蚜可诱导苜蓿的多酚氧化酶活性升高，而丛枝菌根真菌则增强植物抵御蚜虫侵袭及后续苜蓿茎点霉侵染的防御酶活性。此外，在遭受蚜虫侵袭或病原菌侵染的植株中，丛枝菌根真菌可提升体内茉莉酸与脱落酸的含量。在受蚜虫侵袭或病原菌侵染的苜蓿中，脱落酸及与基因本体（Gene Ontology, GO）术语"激素结合（hormone binding）"相关的基因均被上调表达。
讨论：本研究结果表明，丛枝菌根真菌可增强蚜虫侵袭所诱导的植物防御与信号通路组分，这可能有助于提升植物对后续病原菌侵染的防御能力。