Effect Of Potential Allelochemicals From Ramie On Rhizosphere Microbial Diversity And Physiology And Biochemistry Of Ramie

Ramie and its products are specialty and important export product of China.Ramie root-rotten is an aging reaction or tolerance to environmental stress,which affects its fiber yield and quality seriously.Therefore,it has theoretical and practical significances to study the influence of ramie root-rotten and its mechanism,it will benefit for improving the quality and production of ramie fiber.Pot experiments,field plot experiments and laboratory analysis were carried out to study the root-rotten rate and major economic characters in ramie in a seven years located experiments,and the effect of potential allelochemicals from leach liquors of rhizosphere soil and straw of ramie on rhizosphere microbial diversity and physiology and biochemistry of ramie.The main results were showed as follows:(1)The average root-rotten rates of Zhongzhu-1,Tri-1 and Xiangzhu-3 were 14.71%,and their fiber yield decreased 14.94% compared with their high yield period in a seven years located experiments.As the years went on,the plant height,harvest ratio and bast fiber content were increased,and the stem diameter,ramet number,fresh bark thickness,fresh bark yield and fiber yield were decreased.The fiber yield was extremely significantly correlated with plant height,fresh bark thickness and effective stem(P﹤0.01).By means of path analysis,it showed that the direct path coefficient of the fresh bark thickness to fiber yield was the highest(P=0.4198),and effective stem was the second(P=0.4262).(2)About 20,12 kinds of materials were observed and identified in the leach liquors of ethyl acetate and n-hexane from ramie rhizosphere soil respectively,which consisted of hydrocarbon,ester,organic acid,and so on.The contents of palmitic acid,oleamide,2-methyleicosane,heptacosane,and so on were relative higher.The bacteria belong to 24 Phylum,52 classes,125 orders,213 families,329 genera and 569 species.The advantaged bacteria were Proteobacteria,Acidobacteria,Chloroflexi,Bacteroidetes and Actinobacteria,they accounted for 88.92%~97.45% of total number of bacteria.The fungi belong to 43 Phylum,67 classes,87 orders,102 families,120 genera sand 174 species.The advantaged fungi were Ascomycota,Zygomycota and Basidiomycota,they accounted for 65.59%~81.55% of total number of fungi.(3)The potential allelochemicals of root exudates in ramie were 2,4-Di-tert-butylphenol,hexadecanoic acid,methyl ester,dibutyl phthalate,1,2-Benzenedicarboxylic acid,bis(2-methylpropyl)ester,methyl stearate et al,they were observed and identified from ramie rhizosphere soil water leaching solution by GC-MS.When the ramie plants were treated with high concentration leach liquors of ramie rhizosphere soil,the plant height,stem diameter,aboveground dry matter weight,underground dry matter weight and leaf SPAD value were decreased,and the MDA content and CAT activity of leaf were increased.The ramie rhizosphere soil bacterial communities belong to 33 Phylum,74 classes,141 orders,254 families and 394 genera in different treatments.The advantage bacteria were Proteobacteria and Actinobacteria,they accounted for 49.43%~52.13% and 17.72%~22.51% of total number of bacteria,respectively.The abundance of Proteobacteria was increased and Actinobacteria was decreased,when the concentration of ramie rhizosphere soil water leaching solution was increased.The fungi belong to 6 Phylum,25 classes,70 orders,137 families,203 genera and 298 species.The advantage fungus was Ascomycota which accounted for 58.02%~73.84% of total number of fungi.The proportion of bacteria was decreased and fungus was increased significantly with the treatment of high concentration of ramie rhizosphere soil water leaching solution.(4)Hexadecanoic acid methyl ester,hexadecanoic acid,ethyl ester,2,4-Di-tert-butylphenol,9,12,15-Octadecatrienoic acid,methyl ester,(Z,Z,Z)-,9,12,15-Octadecatrienoic acid,ethyl ester,(Z,Z,Z)-,dibutyl phthalate and other compounds were observed and identified from ramie straw water leaching solution by GC-MS,which were potential allelochemicals of ramie straw.When the ramie plants were treated with high concentration leaching solution of ramie straw,their plant height,stem diameter,aboveground dry matter weight and leaf SPAD value were decreased,and he MDA content of leaf were increased,the POD and SOD activities were increased at first,and decreased afterwards.The ramie rhizosphere soil bacterial community belong to 34 Phylum,74 classes,137 orders,249 families and 399 genera in different treatments,advantage bacteria were Proteobacteria and Actinobacteria,they accounted for 44.72%~51.88% and 13.40%~22.46% of total number of bacteria,respectively.The abundances of Proteobacteria and Actinobacteria were decreased and Saccharibacteria was increased when the treatment with increased concentration of ramie straw water leaching solution.The fungi belong to 6 Phylum,23 classes,68 orders,145 families,224 genera and 347 species,the advantage fungi was Ascomycota which accounted for 73.83%~81.64% of total number of fungi,the dominant genera was Penicillium,which accounted for 25.42%~43.35% of the total fungi.The proportion of bacteria was decreased and fungus was increased gradually at the treatment with increased concentration of ramie rhizosphere soil water leaching solution.