Studies On The Screening And Preliminary Application Of Chitinase Producing Strains

[ Background ]Rice is one of the most important crops in the world.With nearly 50 % of the world's population depends on it.China is the biggest rice-producing and rice-cons uming country.More than 60% of the population in our country regard it as the staple f ood,The total output of every year reaches about 200 billion kilograms.Athough our cou ntry have made great achievement of worldwide interests in planting rice,still faces new challenge.The relative high costs,the low efficiency and the weak international competitiv eness still exists.In ecological environment,the factors influencing the growth of rice chan ges.Every time going beyond the range of rice-restrained, these environmental factors bee ome stress factors of adverse circumstances and do harm to rice,they will bring obvious negative effect on rice growth and cause enormous output and economical losses.The di sease of rice is one of the main adverse circumstance and important factors influencing on the output and quality of rice.Especially for fungi disease, it has the characteristics o f fast infection,great harm and so on.As far as the rice is concerned,three kinds of most harmful diseases are rice blast, rice sheath blight, rice bacterial leaf blight, two of whi ch are fungi disease.Among them, rice blast cause 40%-50% decreasing of production in prevailing year,even no harvest at all.In recent decades,the main measures of preventing and controlling the rice diseases is chemical control.However,chemical control gives rise to serious pollution on soil, atmosphere and water, and destroys the balance of the ecol ogical environment.At the same time it leads to the held-up pesticide in the agricultural byproducts and influences on the human's health seriously. In order to control the grain crop diseases and reduce the quantities of chemical pesticides effectively,the research on biological pesticides and biological controls were paid great attention in the world.Chitinase forming strain is a kind of special microorganisms .This strain can utilize chitin as carbon source to survive and repoduce.And it has the common biochemical ch aracteristics of secreting chitinase.Chitinase can degrade chitin into chitin oligosaccharide, chitin disaccharide,and chitin monosaccharide.The application of chitinase and chitin oligo saccharide on plant resistance are extensively reported.Moreover researches verified that c hitin oligosaccharide can promot the growth of plant.So chitinase froming strain is a kin d of promising fungi-resistant microorgnanism.Therefore,it's a very meaningful work to d o more extensive and deeper researches in this respect.[Objective] Obstain the chitinase producing strains inhibiting pathogen fungi and the a plicaion technology and explore the mechanism of antifungi strain[Content] Obtained one or several chitinase secreting strains capable with inhibiting pa thogen fungi found out the premium conditions and measuring the effect of inhibiting topathogen fungi.This experiment explore the mechanism of strain's fermented liquids by examinng the effect of rice defensive enzymes activity.[Method] The screening method of strains: preliminarily isolation: Chitinase producing strains are screened by the method of transparent zones and use selective medium.The s oil samples(cotton field soil,rice field soil,tangerine garden soil,pond bottom mud,aquacult ure mud ,etc.) and plant organs (roots,stems and leaves from rice,cotton,maize,tobacco le aves and some vegetables) are diluted with sterile water(serial dilution method).when thesamples are diluted to 10-4,10-5,10-6 times,o.5ml dilute solution are put into selective medium and are cultived for 3~5 days and observed wheather the transparent zones are produced. The second separation :Strain were obstained by continuing cultivation.single colony wascultivated in separate medium by serial dilution method.,better strain with bisser of tran sparent zones will be choosed.The third separation:Based on the second separation,the colony was cultivated in the pi ate containing blast p...