| A large number of studies have shown that exogenous microorganisms can regulaterhizosphere micro-structure, promote root development and improve plant disease resistanceor resilience, and also have broad application prospects in solving the problem of cropdiseases, yield and quality decline caused by exacerbate soil degradation or extreme weather.But the knowledge of the interaction mechanism between microbes and plants is limited,which restricted researching and developing of hight efficient, stability and regulationproducts. In this study, the rhizosphere probiotics Streptomyces S506which has the functionof growth-promoting, disease prevention, resilience, and lifting root toxins and tomatoseedlings were as the experimental material. The aim of the study is focus on the preliminarystudy of the mechanism of S506growth-promoting and improving cold&salt-tolerance intomato seedlings. The results will be significance to improve the depth research of interactionof microbes and plants, to reveal the mechanism of crop systemic resistance, to find newpathway of improving crop resilience, to develop efficient bio-control products.The metabolites and the function of dissolving phosphorus ability of S506have beentested. The result showed that S506could secrete plant growth hormone—indole acetic acid(IAA), and has a strongly function of dissolved organic phosphorus, but the ability todissolved inorganic phosphorus is weak.The determination of S506fermentation product knockdown root-knot nematodejuveniles (J2) were carried out. NA was selected as the best medium for S506producingnematode resistance material. The optimal culture conditions, temperature28℃and,fermentation period5d, were obtaind. By knockdown experiment with S506metoblismproducts, which extracted by different solvents, It was cleared that the active ingredients ofknockdown root-knot nematode were non-polar organic matter which could distributed inpetroleum ether and ethyl acetate solvent.The effects of S506on the growth promoting in tomato seedlings has been studied. Itwas cleared that S506obviously promoted the tomato root system growth, and increased thecapillarity root number above3times. Under normal conditions, above and below groundfresh weight increased180.0%and93.2%respectively; dry weight improved132.8%and48.39%respectively. However, above and below ground fresh weight were increased228.5% and101.0%respectively; dry weight increased28.3%and50%respectively under1%NaClstress conditions.Effect of S506on the physiological and biochemical characteristics of the tomatoseedlings in the cold and salt stress conditions also has been studied. The results indicated thatS506could significantly increase the recovery rate of chilling injury of tomato seedlings andobviously improve plant salt tolerance. Under0℃stress condition, comparing with thecontrol, S506could increased the root activity by142.0%, proline content by50.8%, MDAcontent decreased by71.1%, the relative conductivity decreased by60.3%, SOD activityincreased by26.4%. The difference of POD activity and chlorophyll content were notsignificant. However under1%NaCl stress conditions S506could increase root activity by198.1%, proline content by149.6%, the accumulation of MDA decreased by46.4%, therelative conductivity decreased by16.9%. The defferents of SOD and POD activities were nosignificant, chlorophyll-a content increased by73.1%.Semi-quantitative analysis of the expression of tomato proline synthesis rate-limitinggene has implementation under cold and salt stress conditions. The result showed that S506could enhance the expression of tomato proline synthesis rate-limiting enzymegene—tomPRO2.In summary, the Streptomyces S506growth-promoting significantly was bound up withproducing IAA and improving utilization of organic phosphorus. The substances which couldknockdown root-knot nematode were organics which could soluble in petroleum ether andethyl acetate. S506could significantly improve the cold and salt tolerance of tomato seedlingsvia increasing root activity, proline synthesis rate-limiting enzyme gene expression and SODactivity as well as reducing occurrence of membrane lipid oxidation, decreasing MDA contentand cell membrane permeability.In both cold and salt stress conditions, the variation of plant physiological andbiochemical characteristics were basically the same. It implied that S506might be regulate thecold&salt-related gene expression of tomato, or regulate someone particular resistance genesexpression in upstream, which improved the systemic resistance of tomato. The specificdetails should be obtaind by further study. |
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