| ACC (1-aminoeyclopropane-1-carboxylic acid) deaminase-containing plantgrowth-promoting rhizobacteria (PGPR) are considered as one of research hotspots athome and abroad, which has broad application prospects in promoting plant growth anddevelopment, deferring the senescence process of plants, improving the stress resistance ofplants. ACC deaminase can catalyze ACC, the direct precursor of ethylene, into ammoniaand α-ketobutyrate, which can effectively inhibit the endogenous ethylene production anddelay the senescence of plants. It’s reported that ethylene plays an important role inaging process of plants. How to prolong the vase life of fresh cut flowers is always anappealing and interesting research program for scientists and horticulturists all over theworld.In this study, ACC deaminase-containing PGPR were isolated and screened from soiland roots of ethylene-sensitive flowers, and applied into the preservation of fresh-cutcarnations, which was helpful to study the effects of ACC deaminase-containing PGPR ondelaying the aging and prolonging the shelf life of flower. The results are as follows:1. Using ACC as a sole nitrogen source and method of enrichment orientationscreening culture, ten strains of ACC deaminase-containing PGPR were isolated andscreened from soil and roots of carnation and lily. Five isolated strains from carnation,including four strains from its cultivated soil (A, B, C and D), one strain from its roots (X(G)). Five strains from lily, including four strains from its cultivated soil (F, F-a, G and H),one strain from its roots (B (G)). Based on the comprehensive analysis of growthmorphological characters and gene sequences of16SrDNA of all isolated strains in thisstudy, the results indicated that strain B was Erwinia; that strain G was Chryseobacterium;that strains F-a, G and H might be the same strain and showed high homology withErwinia; that strain X(G) and B（G）belonged to Acinetobacte.2. By measuring the growth curve and ACC deaminase activity of ten different strains,ACC deaminase activities of two strains (B and H) were higher than those of other strains,which were respectively0.308±0.032U/mg,0.553±0.045U/mg.3. On the basis of preliminary experiments，different concentrations of bacterialsuspension of B and H stains were selected to investigate their effects on the vase life ofcut carnations. The results suggested that: ACC deaminase-containing PGPR hadsignificant effects on preservation of cut carnations, the ornamental quality of cutcarnations treated by bacterial suspensions was better than that of carnations treated bywater. The vase life of treatment B0.75mL reached26days, which was ten days longer(62.5%) than CK. Flower-sagging rates of treatment H0.75mL and B0.5mL were obviouslylower than other treatments, while flower-sagging rate of CK was the highest among alltested treatments. The ornamental quality of treatment H0.5mL got the highest score (28.5points), while CK was lowest one (26.4points). The relative chlorophyll content decreasedwith the aging process among all treatments, which of treatments H0.75mL, H0.25mL and B0.75mL dropped more slowly than other treatments. Soluble protein content showed thetrend of firstly decrease and then increase, which of treatment B0.25mL was significantlyhigher than that of other treatments. Membrane permeability showed a fluctuant increasingtrend，which of treatments H0.5mL and B0.75mL rose slowly. Treatments B1.0mL,B0.75mL and H0.25mL had effects on reducing the production of MDA and deferring itsaccumulation. SOD activity had no obvious rules among all tested treatments, andbasically displayed a fluctuant increasing trend. SOD activities of treatments B0.5mL,B0.25mL, H1.0mL and H0.75mL decreased rapidly during the beginning period of storage,while SOD activities of treatments B1.0mL, B0.75mL and H0.5mL didn’t fluctuatestrongly during the whole storage period. POD activity showed the trend of first decrease,and increase, then gradually decrease again, which of treatments0.5mL, B0.25mL,B0.75mL and H0.75mL changed not too much. CAT activity showed the trend of firstincrease, and decrease, and then increase again, which of treatment B0.75mL was higherthan that of other treatments. Based on the comprehensive analysis, treatment B0.75mLhad the best effects on preservation of cut carnations among all treatments tested in thisstudy. It was helpful to not only maintain the appearance quality of cut flowers, but alsoeffectively delay their aging process. It’s the first report at home and abroad to utilize ACCdeaminase-containing PGPR as fresh-keeping agents in cut flowers. The method was alsoconsidered as an economical and environment-friendly method during the preservation andtransportation period of cut flowers. It will exert some important and practical significanceof improving ornamental qualities of cut flowers, increasing their export, and enhancingChina’s competitiveness in the international flower market. |
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