To determine the beneficial effect of the combination of phosphite (Phi) and Streptomyces hygroscopicus (S11) on soybean plants infected by Phytophthora sojae, soybean seeds were pre-treated with a suspension of S11, the leaves were sprayed with Phi and the roots were subsequently inoculated with P. sojae zoospores. Seedling growth and colonization of root tissue by the pathogen were monitored and the Phi concentration in the roots was quantified. Finally, the effect of S11 and/or Phi on defense responses and SA and JA production were recorded. Both S11 and Phi inhibited the growth of P. sojae in dual V8 agar cultures, and soybean pre-treatment with S11 and/or Phi reduced further infection in planta. In response to P. sojae, defense genes were upregulated in both tolerant and susceptible soybean varieties, especially in the latter. SA and JA accumulated more in the susceptible variety in response to P. sojae, and the use of S11 and/or Phi prior to inoculation induced a decrease in their production. SA accumulated earlier than JA in soybean roots in response to P. sojae in the tolerant variety, whereas JA accumulated earlier than SA in the susceptible one. As such, S11 combined with Phi significantly reduced P. sojae infection in soybean by delaying and reducing the activation of stress hormones and defense-related genes, offering an efficient mean to manage soybean’s infection by P. sojae.

中文翻译：

---

吸水链霉菌和亚磷酸酯的结合可增强大豆对大豆疫霉菌的防御反应

为了确定亚磷酸酯（Phi）和吸水链霉菌（S11）的组合对受大豆疫霉菌侵染的大豆植物的有益效果，将大豆种子用S11悬浮液进行预处理，然后在叶片上喷洒Phi，然后根系用大豆疫霉菌游动孢子接种。监测病原体的幼苗生长和根部组织定植，并对根中的Phi浓度进行定量。最后，记录了S11和/或Phi对防御反应以及SA和JA产生的影响。在双重V8琼脂培养中，S11和Phi都抑制了大豆疫霉的生长，用S11和/或Phi预处理的大豆减少了植物体内的进一步感染。。响应大豆疫霉，耐受和易感大豆品种中的防御基因均上调，尤其是后者。SA和JA在对大豆疫霉的响应中易感品种中积累的更多，并且在接种前使用S11和/或Phi导致其产量下降。在耐性品种中，大豆对大豆疫霉的反应中，SA在大豆根部的累积早于JA ，而JA在敏感品种中的累积早于SA。因此，S11与Phi的结合可通过延迟和减少应激激素和防御相关基因的激活来显着减少大豆中的大豆疫霉感染，从而提供了一种有效的手段来控制大豆的大豆疫霉病感染。