| Microbial chitinase could inhibit both plant pathogens and pests, and it had not virulent on the nature including animal, people and plants, and it also could not pollute environment. Study on the microbial chitinase and study on its biocontrol and molecular biology against pathogens and insects would be very helpful for developing agricultural products and environment protection. This study, Enriched by the medium containing cell wall of Rhizoctonia solani AG-1, 3 chitinase-producing bacterial strains that could inhibit several plant pathogens and insects obviously were isolated from rice microbial circumstances. We studied on the primary security test, classification and identification of chitinase bacteria, probing into action mechanism of chitinase bacteria to several pathogens, and carry though biocontrol against plant diseases and pests. In order to promote on the chitinase activity, antagonistic activity and rice growth, and increase effects of biocontrol against plant diseases and pests, we carried though mixed-culture test in the biocontrol field at the first time, and it showed that the test was successful. But the environment directly influenced biocontrol with live bacteria easily and the effect of biocontrol was instable. And from the molecular biology angel, we could apply into chitinase much effectively. So we carried though primary study on isolation and purification of correlative function protein, chitinase gene cloning and chitinase gene expression in the E.coli. The main results are summarized as below:1. Study on screening model. Enriched by the medium containing cell wall of Rhizoctonia solani AG-1, 166 chitinase-producing bacterial strains were isolated from roots, leaves and stems of rice, rhizosphere soil, chitin and sderotia buried in the soil. The isolation rate from chitin and sderotia buried in the soil and rice plants grew on the chitin and sderotia (account for 91.1%) was much higher than that of any other original strains (only 8.9%). 24 Strains with higher chitinase activities were chose to test antagonism, three isolates, i.e.C2-1, C2-6 and T3-1, could inhibit rice sheath blight greatly were obtained. The chitinase activities were 25. 5U/ml, 18.0 U/ml, 7.5 U/ml respectively with Boiler method.2. Study on antagonistic spectrum of chitinase-producing bacteria. Adopting the method of antagonistic zone on PDA plates, C2-1, C2-6 and T3-lcouldsignificantly inhibit the growth of several plant pathogens such as M.griesa, Fusarium moniliforme, Xanthomonas oryzae pv oryzae, Sclerotinia sclerotiorum^ Alternaria sp. Fusarium geaminearum^ Botrytis sp. , Aelminthosporium sp. , Aspergillus niger Aspergillus flarus^ Penicillium sp. , Aureobasidium sp. , Col le tori chum sp.. And C2-1 also could kill some pests, and the insecticical effect of C2-1 on Cnaphalocrocis medinalis was 57.77%, 89.88% respectively after 12h and 24h in the lab.3. Study on antagonistic mechanism of chitinase-producing bacterium and primary security test. When C2-1 was added into the liquid substrates of the above plant pathogenic fungi, abnormal phenomena such as twisting, deformation, massed and uneven cytoplasm, exosmosis or bareness happened on the protoplasts through optics microscope and electron microscope. The protoplasts inhibited by C2-1 were cultured again, its growth stopped with protoplasts dying, it indicated that the protoplasts were destroyed badly by chitinase bacteria.4. Study on identification of chitinase-producing bacteria. The bacteria, two of new chitinase-producing bacteria and new biocontrol bacteria, were systematically identified as one of the varieties of Bacillus globisporus and PricnbaciIJus polymyxa respectively. They were both new bacteria, which had not been reported.5. Study on biological control against rice diseases and pests in the field trial. After the biological control identification, it indicated that the effects of C2-1 against rice sheath blight, rice blast, bacterial leaf blight in the field trial were 66. 02%, 71. 73%, 73. 24% respectively. The effects of C2...
|
PDF Full Text Request