اثر تنش خشکی و باکتری های ریزوسفری ارتقادهنده رشد گیاه بر خصوصیات اگرومرفولوژیک بادرنجبویه (.melissa officinalis l)

به منظور بررسی اثر تنش خشکی و تلقیح گیاه با باکتری‌های ریزوسفری، بر خصوصیات اگرومرفولوژیک بادرنجبویه آزمایشی به صورت کرت‌های خرد شده در قالب طرح بلوک‌های کامل تصادفی با سه تکرار در مزرعه تحقیقاتی دانشگاه شهرکرد در سال 1398 انجام شد. تنش کمبود آب در سه سطح (آبیاری کامل، 75 و 50 درصد آبیاری کامل) و تلقیح با باکتری‌های محرک رشد در 5 سطح (شاهد (عدم تلقیح باکتریایی)، تلقیح با باکتری‌های azospirillum lipoferum، bacillus sp. strain a، bacillus amyloliquefaciens و streptomyces rimosus) به ترتیب به عنوان فاکتورهای اصلی و فرعی در نظر گرفته شدند. نتایج تحقیق نشان داد اثر باکتری و تنش خشکی بر ارتفاع بوته، تعداد شاخه‌های اصلی، تعداد شاخه‌های فرعی، وزن‌خشک برگ، وزن‌خشک ساقه، سطح برگ، درصد اسانس، عملکرد بیولوژیک و عملکرد اسانس معنی‌دار بود. افزایش شدت تنش منجر به کاهش در تمام صفات مورد بررسی شد درحالی که تلقیح گیاهان با باکتری‌ها نقش مهمی در افزایش این صفات نسبت به شاهد نشان داد و کمترین مقادیر در تیمارهای بدون تلقیح مشاهده شد. با توجه به نتایج این آزمایش به منظور بهبود خصوصیات آگرومورفولوژیک و عملکرد کمی و کیفی بادرنجوبه در شرایط آبیاری کامل و روش‌های کم آبیاری، تلقیح گیاه با باکتری‌های b. amyloliquefaciens ، a. lipoferum و s. rimosus توصیه می‌شود.

The effect of drought stress and plant growth promoting rhizobacteria on agro-morphological characters of lemon balm (Melissa officinalis L.)

IntroductionLemon Balm (Melissa officinalis L.) as an aromatic medicinal plant belongs to the genus mentha and has a variety of uses. Nowadays, due to the increasing popularity of medicinal plants, the area under these plants’ cultivation continue to increase. However, problems such as environmental stresses limit the development of these plants’ cultivation. Drought stress is one of the most important factors limiting the growth and yield of agricultural products around the world. The use of growthpromoting rhizosphere bacteria (PGPR) as a biofertilizer with the aim of reducing the damage caused by environmental stresses is considered as one of the new solutions in sustainable agriculture in arid and semiarid regions of the world. In this regard, this study was designed and conducted to investigate the effect of plant growth promoting rhizobacteria on agromorphological characters of Lemon Balm under water deficit stress Materials and methodsThis experiment was done during 20182019 growing season at the research field of the faculty of agricultural, Shahrekord University as splitplot factorial in a Randomized Complete Block Design with three replications. water deficit in three levels (full irrigation, 75 and 50 present of full irrigation) and inoculation with PGPRs at five levels (Control (No bacterial inoculation), Inoculation with Azospirillum lipoferum, Bacillus sp. strain A, Bacillus amyloliquefaciens and Streptomyces rimosus) considered as main and sub factors, respectively. The amount of irrigation water was calculated using plant water requirement. Leaf area was measured with Digimizer software. After harvesting, first the plant height was measured and then the number of main and subbranches was counted and the leaf dry weight, stem dry weight and biological yield were determined. SAS and Excel softwares implemented for statistical analysis and the means were compared using LSD test. Results and discussionThe results showed that the effect of bacteria and drought stress on plant height, number of main branches, number of subbranches, leaf dry weight, stem dry weight, leaf area, essential oil percent, biological yield and essential oil yield were significant. With increasing stress intensity, all studied traits were decreased. So that by applying 50% of full irrigation, plant height, leaf area and biological yield were reduced by 39.4%, 67.4% and 60.5%, respectively, compared to full irrigation treatment. While inoculation of plants with PGPRs caused a significant increase in these traits compared to the control treatment (No bacterial inoculation). The interaction effect of the studied treatments on the number of main branches, number of subbranches, stem dry weight, leaf area, essential oil percent, biological yield and essential oil yield was significant. At full irrigation treatment, the highest biological yield was observed in inoculated treatments of Azospirillum lipoferum and Bacillus amyloliquefaciens, which increased biological yield by 58.2% and 53.09%, respectively, compared to the control. At 75 and 50% of full irrigation treatments, the highest biological yield and essential oil yield were observed in inoculated treatments of Azospirillum lipoferum and Bacillus amyloliquefaciens. In all the studied treatments, increasing the intensity of drought stress reduced the biological and essential oil yield, but inoculated bacteria were able to increase the biological and essential oil yield compared to the bacterial control treatments. ConclusionThe results of this study showed that increasing water deficit stress causing significant reduction of all studied traits. However, the use of bacteria reduced the effects of stress and increased these traits compared to noninoculated at all water deficit stress levels. Also among bacterial treatments, Bacillus amyloliquefaciens, A. lipoferum and S. rimosus had the most effect on stress improvement.