Study On The Antagonistic Microorganism Of Pyricularia Grisea

A total of 125 strains were isolated from rice leaf,stem and soil. Among these strains, we obtained 61 strains microorganism to have the different degree resistance to Pyricularia grisea through panel confrontation measurement, inhibitation zone of 22 strains exceed 13mm(18 strains bacteria, 4 strains actinomycete).A actinomycete which was strong resistant to Pyricularia grisea and was named as A11.it's inhibitation zone was 18mm and the inhibitation zone of the fermentation products was 12mm.According to the morphological, culture , physiological and biochemical characteristic,it was identified to Norcardia sp..Through fermentation medium screen experiments,we obtained the optimum medium composition.corn 2.0g,starch 2.0g,soybean 5.0g,NaCl 1.5g,water 100ml.the optimum fermentation condition of strain A11 was also determined,which indicated that antibiotics of strain A11 had strong inhibition activity with the initiative pH of 7.2,100ml/250ml medium volume,28℃ temperature, 140r/min rotatory velocity and fermentation 6 days.The result of orthogonal experiment of fermentation condition shows that the effect of pH is significant.The effect degree of three factors is pH>poured solution volume >culture time.It was shown that the fermentation of A11 is not stable to temperature,it can keep inhibition activity at 75 ℃ while the inhibition activity falls down at 100℃;it is stable in neutral acid and alkline situations while the inhibition activity falls down in extra acid and extra alkaline situations.the activity of the fermentation would be reinforced when the initiative pH is 7.2.By means of mycelium growth rate we measured the antibiogram of Al 1 strain,it's fermentation products were tested against Bipolaris maydis, Exserohilum turcicum, Rhizoctonia solani, Fusarium vasinfectum, Colletotrichum gloeosporioi and so on.Theresults showed that the fermentation products of All can resist many plant pathogenic fungus.By organic solvent extraction^ was ascertained that the active substance can dissolve organic solvent.By silica gel columns chromatography and layer chromatography we obtained two active substances,they were yellow oil form things after condensed.Functional group experiment revealed that the active substances have indican or hydroxybenzene hydroxyl.