تولید دو قارچ بیمارگر حشرات، Metarhizium anisopliae و Beauveria bassiana، با استفاده از روش تخمیر دو مرحله‌ای

نوع مقاله : مقاله پژوهشی

نویسنده

• مریم راشکی

گروه تنوع زیستی، پژوهشکده علوم محیطی، پژوهشگاه علوم و تکنولوژی پیشرفته و علوم محیطی، دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته، کرمان، ایران.

چکیده

کلیدواژه‌ها

• آب پنیر
• بستر جامد
• قارچ‌ بیمارگر حشرات
• کنیدی

موضوعات

• کنترل بیولوژیک آفات

Extended Abstract

Entomopathogenic fungi often cause high levels of epizootic disease in nature, and biological control agents are broad-spectrum and environmentally safe. Global cheese production generates more than 100 million tonnes of liquid whey per year, which, if discarded, is considered an environmental pollutant. Cereals and agricultural wastes are used as the main substrates for the mass production of entomopathogenic fungi in different regions of the world, depending on their suitable transport characteristics and cost. In the current research, a diphasic fermentation method involving the production of spores in whey and then injection into solid substrates including rice, wheat, sorghum, barley and wheat bran was used to produce aerial conidia and various parameters such as the number of spores produced, the percentage of viability and the amount of resistance to different temperatures were investigated. Two isolates of pathogenic fungi, including Metarhizium anisopliae var acridum and Beauveria bassiana Z1, whose pathogenicity on various pests had been previously studied, were used to carry out the experiments and investigate the mass production process of conidia. For the first stage, cultivation and multiplication of spores in the whey, the liquid culture medium containing 87.5 g of whey powder in one litre of distilled water was prepared and autoclaved. In contrast, another culture medium containing 20 g of dextrose plus 20 g of yeast in one litre of distilled water was prepared and autoclaved. In the case of solid substrate fermentation, five substrates were prepared, including wheat, barley, rice, sorghum, and wheat bran. Two hundred grams of each substrate except bran were washed with tap water and then dried and poured into five-litre plastic bags with 100 ml of water. All substrates were autoclaved. To aerate the substrates, the open part of the bag was passed through a plastic cylinder and then covered with a layer of cloth, paper towels, and aluminium foil, respectively. After 72 hours, the amount of spores obtained in liquid culture media was checked. Whey was a more suitable culture medium for the cultivation and production of submerged spores. The results showed that the highest amount of conidia of M. anisopliae per ml was significantly obtained from rice and wheat bran. The lowest amount of conidia production also belonged significantly to sorghum. The highest number of B. bassiana conidia per ml was obtained from wheat bran. Then, the wheat substrate produced the highest amount of conidia. The lowest amount of conidia also belonged significantly to barley. For M. anisopliae, the viability of conidia obtained from all substrates except sorghum was 100% and there was a significant difference between these two groups. The results showed that for B. bassiana, the viability of conidia obtained from all substrates except barley was 100% and there was a significant difference between these two groups. The viability percentages of both isolates were determined at ambient temperature on rice and wheat, respectively, after 11 days.The mean viability percentage of M. anisopliae was 97.2%. This value was 100% for B. bassiana. The moisture content of cooked rice and wheat was 60.96% and 40.96%, respectively. One gram of conidial powder of M. anisopliae obtained from sieving rice and B. bassiana obtained from wheat sieving contained about 2.85×10¹⁰ and 3.09×10¹⁰ conidia, respectively. The results for B. bassiana Z1 showed that the viability percentage of conidia after eight weeks of storage was maintained at the same level of 100% in all ratios of talc powder and without talc powder. However, for M. anisopliae, the viability percentage of conidia increased significantly with the increase in talc powder. In addition, without the presence of talc powder, the viability rate of M. anisopliae var acridum decreased from 97.2 to 72.40%. The results of the present research showed that the two-phase method using whey was successful for both isolates and led to proper conidia production in the solid fermentation phase. This diphasic method with the described combination was carried out for the first time for insect pathogenic fungi mass production. Future studies should aim to optimise the mass production process based on whey, cereal grains and agricultural waste. An important issue in the mass production of entomopathogenic fungi is screening the substrates to harvest conidia, especially wheat bran. Using advanced technologies, equipped digital sieves and shakers with specific settings for each substrate should be designed and built to obtain the maximum yield by avoiding conidial waste.