Preliminary Studies On The Mutative Breeding Of The Antibiotic-Producing Strain-024

024 strain, which was screened from soil by Plant Pathology Lab. ofHenan agricultural university, inhibits Rhizotonia cerealis intensely which can cause Wheat sharp eyespot. Based on previous research, it was found that 024 strain showed its inhibitory effect by producing antibiotic. Seeing that 024 strain is a wild-type one, this paper studied its biological characteristics firstly, and then, taking 024 strain and Rhizotonia cerealis as a starting strain and an indicative strain respectively, its spores were treated by some physical and chemical factors to improve it using mutative breeding. Finally, 5 high-yield strains were obtained. At the same time, the mutative effects of all mutative factors in the experiment were evaluated and compared with each other, too. The main content of this paper is described as the following:1) 024 strain's biological characteristics: In all culture media which were tested, Potato Dextrose Agar (PDA) was the best one for 024 strain growth, on which there was the most spore population after it was cultured for 3 weeks. By the fermenting experiment in shaking flasks, it was showed that the fermenting period of 024 strain was about 168h. During this process, there was the biggest value on the growth of mycelium and the yield of antibiotic after 024 strain was fermented for 72h and 96h respectively. Compared with the initial pH7.0, the pH of the fermenting liquid showed that there was a decline (from Oh to 12h, showing acid) firstly, and then, there was a rise (after 12h, showing alkalinity). On the volume of fermenting culture medium in shaking flasks, 024 strain had no strict request. In all inoculation volume treats, 1% was the best one.2) After 024 strain was treated by different mutative factors, the results showed that they had different mortal effect on it. By mutative breeding and the initial screening method of culturing face to face on a plate, 26 high-yield strains were obtained, of which 7 ones were from microwave treat, 19 ones were from Ar-merhyl-A/-nitro-./V-nitrosoguanidine (NTG) treat and no one was from ultraviolet treat or LiCl treat.3) By analyzing and comparing the mutative effects of different mutative factors, it was concluded that the mutative effects of NTG and microwave were more intense than those of LiCl and ultraviolet, of which NTG was the most intense one.4) By fermenting 26 high-yield strains from the initial screening in shaking flasks, 7 ones of them were thought to be high-yield ones, of which there were 5 ones including Nl-32, MW50s3, Nl-2, Nl-20 and MWlOOsis whose inhibitory effects were more over 10%than that of 024 strain. Compared with 024 strain, their inhibitory effects were improved 15.52%, 14.38%, 12.95%, 12.19% and 10.19% respectively...