Construction And Function Study Of A Novel Multi-functional Microbial Community For Rice Straw Incorporation

In order to resolve the two important problems, slow decomposition of rice straw thatretard the growth of the next crops and rice sheath blight pathogen accumulation in soil,caused by rice straw incorporation, a dual-functional microbial community having thefunctions of rice straw degradation and rice sheath blight pathogen inhibition wasconstructed, by combining the selected natural microbial community with rice sheathblight biocontrol strains. Further, the function of the constructed dual-functional microbialcommunity was characterized. The results were as follows:Natural microbial community samples were taken from forest and the soils under ricestraw piles. Microbial community with high ability of rice straw degradation was selected,according to the criterions of highest weight-losing rate of rice straws, CMCase activity andFPAase activity. During the whole process of fermentation, the pH value decreased at theinitial stage and then slightly increased at the later stage. The CMCase activity and FPAaseactivity showed an increase at the beginning and followed by an obvious decrease, with thepeak values of15.31IU/ml and1.8IU/ml, respectively, At the end of fermentation, thedegradation rate of hemicellulose, cellulose and lignin were54.48%,46.48%and4.44%.。The weight of straw reduced by34%.To screen strains with the potentials of Rice Sheath Blight pathogen inhibition, andutilization of rice straw to maintain growth, four bacterial strains of Bacillus and nineTrichoderma strains were studied. The results showed that Bacillus B4and TrichodermaT3、T5、T6and T9had much better degradative ability than the other strains; Inhibitionrates of Bacillus B4was40.48%against Rice Sheath Blight pathogen on dual culture andinhibition zone could maintain stable. Trichoderma T3、T5、T6and T9had higherinhibition rate, and the inhibition rates were46.48%、45.63%、50.99%and53.38%. Themetabolites from the five strains could inhibit the growth of Rice Sheath Blight pathogenand prevent the formation of sclerotium completety.An accurate Real-time PCR quantification method to detect the number of RiceSheath Blight pathogen in soil was established. The specific primer pair and probe weredesigned based on the internal transcribed spacer region of the fungal ribosomal DNA.Standard curve was made by using the plasmid containing the ITS rDNA of the targetstrain. Further, this method was verified by adding a concentration gradient of pathogen insoil. Correlation coefficient and amplification efficiency of the standard curve were0.998and99.7%, respectively. The control showed no signals, and the correlation coefficient between the tested data and the real pathogen number was0.954.The dual-functional microbial community was constructed by combining selectednatural microbial community having high capacity of cellulose degradation with selectedstrain having the function of Rice Sheath Blight pathogen inhibition. Rice strawdegradation capacity was investigated by weight-loss method and the Sheath Blightpathogen inhibition function was evaluated by Real-time PCR method. A dual-functionalmicrobial community was constructed successfully. After12days of fermentation, the totalrice straw weight reduced by41.4%. The degradation rate of hemicellulose, cellulose andlignin were59.5%,52.5%and15.3%. The average CMC enzyme activity during theprocess of degradation was3.1IU/g. The Rice Sheath Blight pathogen decreased by25.2%after40days, and the control treatment decreased by2.9%. This dual-functional microbialcommunity was both effective in rice straw degradation and sheath blight pathogeninhibition. It can be used in rice straw incorporation.