Pythium species are devasting pathogens causing major crop losses, e.g., damping-off in sugar beet caused by Pythium ultimum and root-rot of tomato caused by Pythium aphanidermatum. The use of natural antagonistic microorganisms is a promising environment-friendly approach to control Pythium-caused plant diseases. There are several examples of biocontrol of diseases caused by Pythium species but the application of bioeffectors (biological control agents) is limited for various reasons, including the restricted amount of gene-modification based biotechnological progress. The regulations in many countries prevent genetically modified bioeffectors from being routinely deployed in field conditions. Our two connected aims in this review are (1) to compile and assess achievements in genetic modification of bioeffectors which have been tested for parasitism or antagonism towards a Pythium plant pathogen or biocontrol of a plant disease caused by a Pythium species, and (2) discuss how a better performing bioeffector could be engineered to improve biocontrol of Pythium-caused plant diseases. We focus on the role of seven key mechanisms: cellulases, carbon catabolite de-repression, glycosylation, reactive oxygen species, chitin re-modelling, proteases, and toxic secondary metabolites. Genetic modifications of bioeffectors include gene deletion and overexpression, as well as the replacement of promoter elements to tune the gene expression to the presence of the pathogen. Gene-modifications are limited to fungal and bacterial bioeffectors due to the difficulty of gene modification in oomycete bioeffectors such as Pythium oligandrum. We assess how previous gene modifications could be combined and what other gene modification techniques could be introduced to make improved bioeffectors for Pythium-caused plant diseases. The broad host-range of Pythium spp. suggests engineering improved antagonistic traits of a bioeffector could be more effective than engineering plant-mediated traits i.e., engineer a bioeffector to antagonise a plant pathogen in common with multiple plant hosts rather than prime each unique plant host.

腐霉是破坏性病原体，造成重大作物损失，例如，由终极腐霉引起的甜菜猝倒病和由空心腐霉引起的番茄根腐病。使用天然拮抗微生物是控制腐霉引起的植物病害的一种有前途的环境友好方法。有几个由腐霉引起的疾病的生物防治例子但由于各种原因，生物效应器（生物控制剂）的应用受到限制，包括基于基因修饰的生物技术进步的数量有限。许多国家的法规禁止转基因生物效应器在野外条件下常规使用。我们在本次审查中的两个相互关联的目标是（1）汇编和评估生物效应器的基因改造成就，这些生物效应器已经过对腐霉植物病原体的寄生或拮抗作用或对腐霉属物种引起的植物病害的生物控制，以及（2）讨论如何设计出性能更好的生物效应器来改善腐霉的生物控制- 引起的植物病害。我们专注于七种关键机制的作用：纤维素酶、碳分解代谢物去抑制、糖基化、活性氧、几丁质重塑、蛋白酶和有毒的次级代谢物。生物效应器的遗传修饰包括基因缺失和过表达，以及更换启动子元件以调整基因表达以适应病原体的存在。由于卵菌生物效应器（如寡雄腐霉）中基因修饰的难度，基因修饰仅限于真菌和细菌生物效应器。我们评估了如何结合以前的基因修饰以及可以引入哪些其他基因修饰技术来改进腐霉引起的植物病害的生物效应器。广泛的宿主范围腐霉属 表明工程改进的生物效应器的拮抗性状可能比工程化植物介导的性状更有效，即工程化生物效应器以对抗与多种植物宿主共同的植物病原体，而不是引发每个独特的植物宿主。