Institute of Pharmaceutical Biology, Technische Universität Braunschweig, Mendelssohnstraße 1, 38106, Braunschweig, Germany.
Institute of Horticultural Production Systems, Woody Plant and Propagation Physiology Section, Gottfried Wilhelm Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419, Hanover, Germany.
Phytochemistry. 2021 Dec;192:112972. doi: 10.1016/j.phytochem.2021.112972. Epub 2021 Oct 5.
Apple replant disease (ARD) is a severe soil-borne disease frequently observed in apple tree nurseries and orchards worldwide. One of the responses of apple trees to ARD is the formation of biphenyl and dibenzofuran phytoalexins in their roots. However, there is no information on whether or not these phytoalexins are exuded into the soil. To answer this open question, a model system was established using the ARD-sensitive apple rootstock M26 (Malus × domestica Borkh. Rosaceae) and GC-MS analysis in combination with an in-house GC-MS database including retention indices. We have detected a total of 35 phytoalexins, i.e. 10 biphenyls and 25 dibenzofurans in root samples, thereby adding eight compounds to the previously reported 27 phytoalexins of Malinae species. When in vitro cultured M26 plantlets were treated with yeast extract, all the 35 phytoalexins were formed in the roots and 85.2% of the total phytoalexin amount was exuded into the culture medium. In roots of M26 plants grown in ARD soil in pot, 26 phytoalexins were detected and their exudation was demonstrated using two independent approaches of collecting root exudates. In a modified dipping experiment and a soil-hydroponic hybrid setup, the exudation rate was 39.5% and 20.6%, respectively. The exudation rates for individual phytoalexins differed, indicating controlled exudation processes. The exuded phytoalexins may play an important role in shaping the soil microbiome, which appears to greatly influence the development and severity of ARD.
苹果树再植病（ARD）是一种严重的土传病害，在世界范围内的苹果苗圃和果园中经常发生。苹果树对ARD 的反应之一是在其根部形成联苯和二苯并呋喃植物抗毒素。然而，目前尚不清楚这些植物抗毒素是否会分泌到土壤中。为了回答这个悬而未决的问题，我们使用 ARD 敏感的苹果砧木 M26（Malus × domestica Borkh. Rosaceae）建立了一个模型系统，并结合 GC-MS 分析和内部 GC-MS 数据库（包括保留指数）进行了研究。我们总共在根样本中检测到 35 种植物抗毒素，即 10 种联苯和 25 种二苯并呋喃，从而在先前报道的 Malinae 种的 27 种植物抗毒素中增加了 8 种化合物。当体外培养的 M26 组培苗用酵母提取物处理时，所有 35 种植物抗毒素都在根部形成，其中 85.2%的植物抗毒素总量分泌到培养基中。在盆栽中生长于 ARD 土壤中的 M26 植株的根部，检测到 26 种植物抗毒素，并通过两种独立的收集根分泌物的方法证明了它们的分泌。在改良的浸蘸实验和土壤-水培混合装置中，分泌率分别为 39.5%和 20.6%。个别植物抗毒素的分泌率不同，表明存在受控的分泌过程。分泌的植物抗毒素可能在塑造土壤微生物组方面发挥重要作用，而土壤微生物组似乎极大地影响了 ARD 的发展和严重程度。
