مهار زیستی بیماری پژمردگی باکتریایی لوبیا با استفاده از عوامل زیستی pseudomonas fluorescens و trichoderma harzianum

استفاده از روش‌های جایگزین سموم شیمیایی، برای تولید محصولات ارگانیک از اهمیت بالایی در کشاورزی پایدار برخوردار است. یکی از این روش‌ها استفاده از عوامل زیستی میکروبی علیه بیمارگرهای گیاهی است. در پژوهش حاضر نیز اثر عوامل آنتاگونیستی p. fluorescens و t. harzianum علیه بیماری پژمردگی باکتریایی لوبیا با عامل curtobacterium flaccumfaciens pv. flaccumfaciens (cff) در شرایط آزمایشگاه و گلخانه سنجیده شد. بدین منظور بعد از تهیه عوامل میکروبی، ابتدا اثر جلوگیری کننده از رشد باکتری cff با دو روش کشت متقابل عوامل زیستی و مواد مترشحه آن‌ها در شرایط آزمایشگاه بررسی شد. سپس اثر این عوامل زیستی روی شدت و روند پیشرفت بیماری ایجادشده توسط cff و همچنین شاخص‌های گیاه لوبیا در شرایط گلخانه، طی چهار تکرار و در قالب طرح کاملاً تصادفی سنجیده شد. نتایج پژوهش حاضر نشان داد در شرایط آزمایشگاه عوامل آنتاگونیست p. fluorescens و t. harzianum به‌ترتیب 18.67 و 27.33 درصد و مواد مترشحه آن‌ها 16 و 13.67 درصد از رشد باکتری cff جلوگیری کردند. در شرایط گلخانه تیمارهای p. fluorescens و t. harzianum و ترکیب این دو عامل با هم، به ترتیب 50.62 و 55.32 و 36.25 درصد، شدت بیماری را کاهش دادند. همچنین این سه تیمار به ترتیب 40 و 34.07 و 57.04 درصد، علائم بیماری را کاهش دادند. همچنین تیمار ترکیبی دو عامل زیستی بیشترین اثرگذاری را روی کاهش بیماری و افزایش شاخص‌های گیاه لوبیا نشان داد. لذا عوامل زیستی بکارگرفته شده می‌توانند به‌عنوان عوامل مهار‌زیستی بیماری پژمردگی باکتریایی و افزاینده رشد گیاه لوبیا باهدف کاربردی نمودن آن‌ها در مطالعات آینده موردتوجه قرار گیرند.

biocontrol of bean bacterial wilt disease using pseudomonas fluorescens and trichoderma harzianum biological agents

background and objectivescurtobacterium flaccumfaciens pv. flaccumfaciens is the cause of bean bacterial wilt (cff) and a dangerous pathogen for bean fields. to date, no definitive control has been found for this pathogen. in sustainable agriculture, it is used to control plant pathogens by applying management methods related to preserving the environment and producing organic products. the use of biological agents such as trichoderma fungi and pseudomonas bacteria is among these management methods. minimal research has been done worldwide on biological agents’ effects on cff. therefore, the present research will investigate the effect of inhibiting the growth and activity of two biological agents‌, including pseudomonas fluorescens and trichoderma harzianum, against cff in laboratory and greenhouse conditions.materials and methodsfirst, the pathogenicity test of cff was carried out on the greenhouse’s sadri variety pinto bean plant. then, the effect of fungal and bacterial biological agents against the pathogenic agent was investigated by two methods of mutual culture and their secreted substances in laboratory conditions. by measuring the diameter of the transparent halo formed around the extract and spot culture of biological agents, the growth inhibition power of these biological agents against cff was evaluated. in order to investigate the effect of these biological agents against bacterial wilt disease in greenhouse conditions, these biological agents and pathogens were propagated and expanded, and a standard suspension was first prepared from them. these suspensions were inoculated on the host plant using the spraying method. during 21 days, disease symptoms and bean plant indicators have been recorded. then, the disease severity of progress under the influence of these biological factors was checked using the 0 to 4 scoring system. also, the plant resistance type to the pathogen was evaluated using the 1-5 scoring system. the data obtained from the laboratory (inhibition percentage) and greenhouse (treatment changes, plant resistance, and plant indices) studies were analyzed in a completely randomized design using spss 21 software.resultsin laboratory conditions, p. fluorescens and t. harzianum treatment prevented the growth of pathogenic bacteria cff by 18.67 and 27.33%, with a diameter of the inhibitory halo of 14 and 20.5 mm, respectively. it was also found that a significant part of the inhibitory effect of p. fluorescens bacteria (about 85.70%) is related to the secreted substances of the bacterial cells. in contrast, in the biological fungus t. harzianum, the effect of the secreted substances was about 50.02%. the effect of biological factors on cff in greenhouse conditions showed that these biological factors strengthen the defense reaction of bean plants against cff. so, the sensitive reaction of the plant against cff bacteria (with a disease severity of 83.13%) was transformed into a semi-resistant reaction by inoculating p. fluorescens and t. harzianum with the diseased plant. also, the inoculation of the combination of these two biological factors made the plant resistant to pathogenic bacteria. treatment of p. fluorescens+t. harzianum, by affecting cff bacteria, was the best treatment in reducing the severity of the disease during 7, 14, and 21 days; the severity of the disease on these days was 21.87, 33.12, and 36.25%, respectively, which showed a significant difference with the disease severity index in infected treatment during these few days at the statistical level of 1%. treatment of p. fluorescens+t. harzianum, with a disease severity index of 36.25% and a 57.04% reduction in disease severity, showed the most significant effect on the reduction of bean bacterial wilt disease.discussionin the present study, the use of two biological agents, p. fluorescens and t. harzianum, showed significant controlling effects on cff in laboratory and greenhouse conditions, and 57.04% reduced the severity of this disease in the bean plant. these two biological factors prevent the growth and spread of plant pathogens by using mechanisms such as the production of secondary metabolites, acidifying the environment, competing for food and space, colonizing and stimulating the plant to produce phytoalexin, proteins related to pathogens, salicylic acid, etc. therefore, using these two biological agents as safe, effective, and durable biological control agents in sustainable agriculture against bean bacterial wilt disease is recommended.