Morphogenesis Of Ten Different Entomogenous Fungi In Liquid Culture

Blastospores are asexual reproductive spores that originate by budding, as in yeasts and many filamentous fungi. In liquid culture, many fungi reproduce in this form. In the biophasic fermentation technology of industrial production of fungal insecticides, liquid fermentation is needed to supply large amount of highly vital pure blastospores as inocula for the subsequent solid mass production. In addition, the highly vital blastospores are also needed as a receptor for genetic transformation. However, the formation process and morphogenesis of the blastospores of entomogenous fungi have been rarely reported. In the present paper, the development process in liquid culture of ten common entomogenous fungi were studied to compare their morphogenesis, including Beauveria bassiana, Isaria farinosa, I. cicadae, I. cateniannulata, I. fumosorosea, I. tenuipes, I. cateniobliqua, Metarhizium anisopliae, M. acridum, and Lecanicillium lecanii. They were cultivated in liquid media which were most suitable to respective isolates in a50mL culture system of25℃, natural light, and130y/min. The culture of each isolate was sampled every6hours.The results showed two types of development:⑴development of I. cicadae was divided into five stages:①inflation of conidia②germination of conidia；③germ tube elongation④exponential growth of blastospores⑤hypha aging⑵development of the other nine species was divided into six stages:①inflation of conidia②germination of conidia；③germ tube elongation④early growth of blastospores⑤exponential growth of blastospores⑥aging of hyphae and blastospores. Calcium oxalate crystals formed in development of most strains.The morphogenesis of the above ten isolates included two types:①For I. cicadae, hyphal growth took predominance through the whole development, but blastospores rarely produce.②For the other species, blastospores formed in similar way: blastospore formed in large amount by budding or constriction of hyphae soon after mycelium formation,and then by budding or constriction of blastospores. The formation of blastospores can be divided into three phases: in early phase, blastospores formed first by hyphal budding in exponential phase, blastospres multiplied in large number either by hyphae or by blastospors, and in late phase, new blastospores formed mainly by blastospore budding.