Preliminary Study On The Biocontrol Of Peach Yellow Disease By Siderophore-producing Bacterium

As one important fruit trees of the drupe fruit trees, peach, a native fruit tree of China is popular for its beauty, good taste and fruit rich in nutrition. The production of peach was restricted seriously by peach yellow disease which is a greater harm disease. People has tried many ways to recitify this disease, but all the methods they used were not highly effective. Siderophore is a kind of chelate factor with strong affinity to Fe3+, it play an important role in the plant growth promotion and improving chlorosis caused by iron deficiency. So, the method of using siderophore-producing bacterium to control peach yellow disease is feasible. This dissertation included the screening and charecteristics of siderophore-produing bacterium pathogen, mutagenesis and biological control of peach yellow disease, the result as follows:1 Screening and charecteristics of siderophore-producing bacteriumUsing the chrome azural S (CAS) reagents assay, a siderophore-producing bacterium MX-26 was screened out from 81 bacteria, which were isolated from the peach rhizosphere soil. According to morphological, biochemical charecteristics and 16S rDNA sequence analysis, strain MX-26 was classified as Klebsiella oxytoca.2 Mutagensis of siderophore-producing bacteriumAs an original strain, MX-26 was mutated by UV-ray, complex mutagenesis of UV-ray and lithium chloride (LiCl), diethyl sulphate (DES), the optimum mutagenesis conditions were determined as follows:mutated by UV-ray was tested to be 180 seconds, the concentration of lithium chloride should be 1.2% and mutated by the diethyl sulphate was tested to be 40 minutes. The mutants of strain MX26-18 was obtained. Compared with MX-26, the siderophore production from MX26-18 was increased by 32.9%. And the subculture experiments indicated that the hereditary characteristic of MX26-18 was stable. 3 Colonization of siderophore-producing bacteriumA strain resistant rifampin derivative of siderophore-producing bacterium MX26-18 was used to study the colonization ability in peach rhizosphere soil, the contrast was sterilization soil. The result indicated that the population of strain MX26-18 in peach rhizosphere soil was trend to descend in earlier, then trend to increase at the 45 days. At 60 days, the population of MX26-18 was one orders of magnitude more than the intial, but it was remained at 104cfu/g. The growth tendency of MX26-18 in sterilization soil have frew difference with in rhizosphere soil. Although the bacterium number in sterilization soil was reduced nearly half than intial at 60 days, it was still have one orders of magnitude more than in rhizosphere soil. So the result indicated that the strain MX26-18 in the sterilization soil have the higher colonization than in the rhizosphere soil.4 Biological control of peach yellow disease by siderophore-producing bacteriumAt present, there was no report about biological control of peach yellow disease in China. This study was first explored the biological control of peach yellow disease by siderophore-producing bacterium. Regard the disease peach on Tao hua hill of Ya an as experiment objects, the peach was undergo periodic surveys after using the siderophore fermentation liquor and to rhizosphere. The result indicated that the effect was not obvious by fermentation liquor, but the siderophore fermentation liquor has definite control action to peach yellow disease. So, the method of using siderophore-producing bacterium to control peach yellow disease is feasible, but how to use siderophore-producing bacterium to control peach yellow disease on calcareous soil will obviously require further investigation.