پديد آورندگان :
ناظور، علي دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي , ممرآبادي، مجتبي دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي , طاهري، پريسا دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي
كليدواژه :
پژمردگي آوندي , كنجد , مهار زيستي , Trichoderma harzianum
چكيده فارسي :
كنجد يكي از گياهان زراعي با ارزش غذايي فراوان است كه از حمله‌ي ميكروارگانيسم‌هاي بيمارگر از جمله قارچ‌ها، مصون نيست. ايجاد بيماري‌هايي مانند پژمردگي آوندي در اين گياه، باعث كاهش راندمان محصول مي‌گردد. تعداد 17 جدايه مربوط به Fusarium oxysporum f. sp. sesami از گياهان كنجد مشكوك به بيماري در مناطق مختلف استان خراسان رضوي جداسازي شدند. براي بررسي امكان مهار زيستي از قارچ آنتاگونيست Trichoderma harzianum جدايه‌ي TR5 استفاده گرديد. در آزمون بيماري‌زايي تمام جدايه‌هاي F. oxysporum f. sp. sesami بيماري‌زا بوده و از اين نظر با هم داراي اختلاف معنيداري در سطح 5 درصد نشان دادند كه بيش‌ترين شدت بيماري‌زايي مربوط به جدايه‌هاي BA15 و BA16 هر دو با 87/5 درصد پژمردگي و كم‌ترين شدت بيماري‌زايي مربوط به جدايه‌هاي AN7 و KA33 هر دو با 12/5 درصد پژمردگي گياه كنجد بود. در آزمون بررسي آنتاگونيستي در شرايط آزمايشگاهي از روش كشت متقابل بيمارگر با آنتاگونيست استفاده گرديد كه بيش‌ترين ميزان بازدارندگي از رشد ناشي از اثر آنتاگونيستي T. harzianum مربوط به جدايه‌ي BA1 با 88/45 درصد و كم‌ترين ميزان بازدارندگي از رشد ناشي از تقابل با آنتاگونيست مذكور مربوط به جدايه‌ي AN2 با 71/33 درصد بود. هم‌چنين در شرايط گلخانه‌اي ميزان كاهش شدت علائم بيماري در بين جدايه‌هاي مورد آزمايش، متفاوت بوده و اختلاف معنيداري در سطح 5 درصد نشان دادند. بيش‌ترين تأثير آنتاگونيستي T. harzianum روي جدايه‌هاي BA1، AN7 و K33 با كاهش شدت بيماري به ميزان 100 درصد و كم‌ترين تأثير مربوط به جدايه‌ي AN2 با كاهش شدت بيماري به ميزان 54/54 درصد بود.
چكيده لاتين :
Background and Objectives
Sesame is one of the most valuable crops in human nutrition and is cultivated in different regions of Iran, including Khorasan Razavi province. In this plant, various pathogens cause vascular wilt and reduce crop yield. This study aimed to detect the fungal pathogens causing vascular wilt in sesame and control its diseases using the antagonistic fungus Trichoderma harzianum under in vitro and in vivo conditions.
Materials and Methods
Twenty-one suspected sesame samples were collected and transferred to the laboratory to be studied using valid morphological identification keys. Media such as PDA, WA, and CLA were used for the isolation, purification, and identification of the fungal samples isolated from the infected sesame plants, respectively. Pathogenicity test was conducted by the root inoculation of sesame plants grown under greenhouse conditions. The biocontrol activity of Trichoderma harzianum (Isolate TR5) isolated from the rhizosphere of sesame roots was evaluated against the pathogenic isolates of Fusarium oxysporum f. sp. sesami under in vitro (dual culture) and greenhouse conditions by the root inoculation of the plants.
Results
According to the result, 17 isolates were related to Fusarium oxysporum f. sp. sesami. The pathogenicity test was performed on the sesame plants at the 5-8-leaf stage. All F. oxysporum f. sp. sesami isolates were pathogenic as they revealed a significant difference at p=0.05. The highest level of pathogenicity was noticed for the isolates BA15 and BA16, both with 87.5% wilting, and the lowest pathogenicity was observed in the isolates AN7 and KA33, both with 12.5% wilting on the sesame plants. Regarding the antagonistic properties, the highest inhibition rate in dual culture with T. harzianum was observed for the BA1 isolate with 88.45% mycelial inhibition, while the lowest inhibition rate during interaction with the antagonist was exhibited in the AN2 isolate with 71.33% mycelial inhibition.
Moreover, the disease severity reduction rates were different among all isolates of the pathogen tested under greenhouse conditions, and a significant difference was observed at p= 0.05. The highest antagonistic activity of T. harzianum was observed in the BA1, AN7, and K33 isolates with 100% disease severity reduction; however, the lowest activity was related to the AN2 isolate with 54. 54% reduction.
Discussion
The present study indicates that the TR5 isolate belonging to T. harzianum has a high biocontrol potential for controlling vascular wilt on the sesame plants. Consistent with this finding, previous studies have also reported the potentials of Trichoderma spp. for controlling Fusarium wilt in tomatoes, cucumbers, and beans.
