Antimicrobial-resistant Rhizobia Screening And Effect Verification Of Undesired Microbe Control In The Prepared Rhizobia Inoculant

The commercial rhizobia inoculants always encounter the problems of loweffective viable count and high contamination, which limited the shelf life ofinoculants, and meanwhile, after the inoculant be applied to field, it is hard for thetarget rhizobia to compete successfully with indigenous rhizobia that accommodatethe local environment perfectly for nodulation. In order to solve the above problems,this study intended to make clear the anti-contamination effect of rhizobia inoculantof different formulations and carriers, as well as the inoculation effect of resistantrhizobia and antimicrobial on host plant growth by adding antimicrobial to theinoculant. Meanwhile, tri-parental mating method was used to incruduce fluorescentprotein into rhizobia to make them been easily traced. The main obtained results:1: all the selected rhizobia resist botanical antimicrobials better comparedwith rare earth salts. Low concentrations of rare earth salts (0.4mg mL-1) couldinhibit the growth of most rhizobia, while the concentration of which could not inhibitthe growth of most air and soil oriented microbials; in comparison,0.6mg mL-1matrine could inhibit the growth of most air and soil oriented microbials, and underthis concentration, some preliminarily selected rhizobia could still grow.2: to determine the resistant capability variance of the fluorescence markedresistant rhizobia and control rhizobia to antimicrobials, and no extra adverse effectwas found of fluorescence marker on rhizobia resistance, indicating that tri-parentalmating method could be used for rhizobia tracing.3: the addition of0.6mg mL-1matrine inhibited alfalfa plants growth to somedegree, all the tested morphological and physiological indices were foundsignificantly lower than the un-inoculated control, while according to the inoculationof bacteria solution containing the corresponding concentration of matrine, all thetested morphological and physiological indices were found no longer lower than theun-inoculated control, and in some indices like chlorophyll content, soluble sugarcontent, root activity, root length and volume, shoot height, individual leaf and nodule number as well as nodule classification, they reached the level of treatmentsinoculated with control rhizobia, indicating that the addition of antimicriobial intorhizobia inoculants promoted host plants growth as a whole, despite the fact that someindices had been affected, this also furtherly affirms the feasibility of adding matrineas antimicrobial into rhizobia inoculant.4: rare earth salts inhibited air and soil oriented microbials well, while incomparison, they had stronger inhibition effect on rhizobia, which is not good forresistant rhizobia selection, and meanwhile, rare earth salt could react with mostmedia components and pH modifier because of its active chemical property, whichbrought pratical diffculty in the successive rhizobia culture, and therefore is notsuitable to be used as additive of rhizobia inoculant.5: pyrethrine had good inhibitory effect in short period, but the effectdecreased as the delay of time, and higher contents of inhibitory substances isrequired to achieve good inhibition effect, together with its requirement for lowtemperature and dark environment, as well as high practice, it is not a good choice forrhizobia inoculant additive compared with matrine which has relatively cheaper price,longer inhibition time and requires relatively lower contents of inhibiton substances.6: according to the anti-contamination determination of rhizobia inoculantscontaining matrine, the undesired microbe number in both the liquid and soilidinoculants had been significantly decreased, the contamination rate had also beeninhibited as expressed in indices like undesured microbe rate, and meanwhile, pHvalue of the solid inoculant had also been well controlled, and therefore, matrinecould be used as additive of liquid and soild rhizobia inoculant.