جداسازی باکتری ‌های ریزوسفری sp. pantoea و sp. pseudomonas و بررسی توانایی آن ‌ها در مهار زیستی pectobacterium carotovorum subsp. carotovorum عامل لهیدگی غده‌ها و سبزیجات

Pectobacterium carotovorum subsp. carotovorum (pcc) (pcc) از مهمترین عوامل لهیدگی سبزیجات و غده های سیب زمینی در ایران و جهان می باشد. در این پژوهش جهت کنترل این بیماری با عوامل مهار زیستی ، 12باکتری از ریزوسفر سبزیجات کاهو، پیاز، کلم، سیر، هویج، فلفل دلمه ای و سیب زمینی جداسازی گردید و علیه دو جدایه بیمارگر pcc به کار رفت. جدایه a10 pantoea توانایی ایجاد هاله بازدارنده روی محیط کشت علیه بیمارگر را داشت و از توانایی مهار زیستی مناسبی علیه یک جدایه بیمارگر روی سبزیجات و غده سیب زمینی برخوردار بود. همچنین 12 باکتری ریزوسفر از سبزیجات و سیب زمینی به منظور بررسی قدرت quorum quenching (qq) جداسازی گردیدند. تنها جدایه ss5 pseudomonas هم در آزمون بیوسنسور توانایی qq نشان داد و هم توانست لهیدگی ایجاد شده توسط هر دو جدایه بیمارگر را در مقایسه با شاهد کاهش دهد. این دو باکتری اثرات منفی رشدی در محیط کشت علیه همدیگر نشان ندادند، لذا در ترکیب با یکدیگر در آزمون های کنترل لهیدگی غده به کار رفتند. نتایج  نشان داد توانایی مهار زیستی این دو باکتری در حالت ترکیبی عملکرد بهتری در  مقایسه با کاربرد جداگانه هر یک از آن ها دارد به نحوی که وزن بافت لهیده سیب زمینی از 2.41 گرم در شاهد و 1.1 گرم در کاربرد بهترین باکتری با توانایی مهار زیستی (ss5)، به 0.5 گرم در حالت کاربرد ترکیبی دو باکتری کاهش یافت. نهایتاً این تحقیق برای اولین بار توانایی کنترل pcc با اثرات هم افزایی دو باکتری sp. pantoea وsp.   pseudomonas با دو مکانیسم مختلف را نشان داد.

isolation of rhizospheric pantoea sp. and pseudomonas sp. bacteria and evaluation of their bio-control ability against pectobacterium carotovorum subsp. carotovorum causes of tubers and vegetables rot

pectobacterium carotovorum carotovorum (pcc) is one of the main causes of soft rot disease in many economically important vegetables and tubers such as carrot, cabbage, potato, onion, cucumber, eggplant, garlic, bell pepper, radish, sweet potato, squash and tomato. the use of chemical bactericides is not suitable to control soft rot bacteria due to their toxic side effects and the emergence of resistance in bacterial populations. the use of bio-control bacteria to inhibit bacterial pathogens such as pcc is a practical and useful method to overcome the issue. in this study, in order to control this disease with the help of bacterial biological control agents, some bacteria were isolated from rhizosphere of vegetables and potato. the aim of this study was to find bacteria with different bio-control mechanisms which are able to inhibit different isolates of pcc. on the other hand, these bacteria (with different bio-control mechanisms) were combined to investigate the possibility of increasing their bio-control ability in a mixed manner.2.materials and methods: 12 rhizospheric bacteria were isolated from vegetables and potato. antibacterial properties were evaluated using chloroform vapor method. also, 12 bacteria were isolated from rhizosphere of vegetables and potato by minimal medium to evaluate the quorum quenching (qq) ability. chromobacterium violaceum cv026 biosensor was used to assess qq activity in bacteria. there were two types of bio-control tests: the first case was the application of bacteria individually and the second case was the mix of bacteria with different bio-control mechanisms, antibacterial property and qq activity, and its application against two strains of pcc including pcck and pccm. at first, before doing the second bio-control test, interaction test between bio-control bacteria was performed by culturing two bacteria perpendicular to each other on solid medium. bio-control test of pcc on plant tissues (potato tubers, carrots and bell peppers) was performed by calculating the weight of rotting tissue in comparison with the control (containing pcc alone). classical and molecular bacteriological tests were performed to detect these bacteria.3.results and discussion: among rhizospheric bacteria with antibacterial properties, a10 isolate had a large inhibitory halo, 16.67 mm, against one strain of pcc (pcck) and it had the ability to bio-control of pcck on vegetables and potato tubers. among bacteria, only ss5 isolate showed qq ability in both biosensor and bio-control tests. a10 and ss5 were detected as pantoea and pseudomonas sp. respectively. pseudomonas ss5 had moderate bio-control activity against two pcc strains with qq mechanism as inhibition percentage on potato tubers rot for pccm and pcck were 53.92 % and 68 %, respectively. pantoea a10 with antibacterial activity which had low or high bio-control properties against pcc strains as inhibition percentage on potato tubers rot for pccm and pcck were 5.81 % and 91.33 %, respectively. the bio-control effect of a10 and ss5 bacteria against pcc strains on carrots and bell peppers was better than potatoes. the interaction of two bacteria on solid medium, ss5 and a10, was not visible as a transparent area at their intersection, so they did not show an inhibitory effect against each other. therefore, it is possible to use combination of two bacteria, a10 and ss5, for bio-control tests.