Phytoalexin formation in apple roots responding to apple replant disease (ARD) soil

苹果是一种珍贵的果树，但其繁殖受到苹果再植病（ARD）的影响，导致枝条和根系生长受阻。其原因尚不清楚，但根际微生物组的变化似乎起着重要作用。最近，我们的合作伙伴在ARD土壤中的敏感砧木M26植物中观察到生物量下降和根系损伤，与热处理和伽马辐照土壤中的根系相比。第一次，发生联苯和二苯并呋喃植物抗毒素在受影响的根，然后检测。此外，我们还观察到植物抗毒素从激发子处理的体外生长根中分泌到培养基中，这表明化合物从ARD土壤中的根释放到根际。我们将研究各种离体生长的砧木基因型诱导子处理后的定性和定量的差异，在他们的植保素生产。还将测试从ARD土壤中丰富物种中提取的激发子制剂。主要的植物抗毒素将被合成并检查它们对各种根际（微生物）生物的影响。预计这些影响将导致生物群落组成的变化。植物抗毒素对根的活性也进行了研究，揭示了潜在的化感作用和自毒作用。此外，还研究了植物抗毒素在干旱胁迫下生物合成的时空调控。我们的研究结果将有助于了解复杂的变化，在土壤中，苹果生长引起的，并在苹果本身种植到ARD土壤。

Apple is a valuable fruit tree, however, its propagation is affected by apple replant disease (ARD), which leads to stunted growth of shoots and roots. The causes are poorly understood but changes in the microbiome of the rhizosphere appear to play an important role. Recently, biomass decline and root damage have been observed by our cooperation partner in susceptible rootstock M26 plants in ARD soils, when compared to roots in heat-treated and gamma-irradiated soils. For the first time, occurrence of biphenyl and dibenzofuran phytoalexins in ARD-affected roots was then detected. In addition, we have observed exudation of the phytoalexins from elicitor-treated in vitro-grown roots to the culture medium, suggesting release of the compounds from roots in ARD soils to the rhizosphere. We will study various in vitro grown rootstock genotypes after elicitor treatment for qualitative and quantitative differences in their phytoalexin production. Elicitor preparations from abundant species in ARD soils will also be tested. The major phytoalexins will be synthesized and examined for their effects on various rhizosphere (micro)organisms. These effects are expected to cause changes in the biome composition. The activity of phytoalexins toward roots is also examined, revealing potential allelopathy and autotoxication. Furthermore, the temporal and spatial regulation of phytoalexin biosynthesis in ARD-affected roots is studied. Our results will contribute to understanding the complex changes in soils, caused by apple growth, and in apple itself when planted into ARD soils.