Isolation And Identification Of Endophytic Bacterial Isolates Ferom Alfalfa

There are endophytes in almost all the healthy plants. Beneficial endophyticbacteria can make beneficial effects on the host plants. Endophyte can stabilitily andlong-lasting act on the host plant bacause of its stable ecological niche, which caused awidespread concern and plants’ and micro-biologists’ focus. Alfalfa (Medicago sativa)is perennial herbaceous legume with the name of "king of grass". The aim of this studywas to isolate and select endophytic bactieria from Medicago sativa, to study thegrowth-promoting effects biocontrol activity of the selected endophytic bactieria and toprovide sencitist base for bactieria fertilizer and biological pesticides, which is veryimportant.1. Eight endophytic bactieria strains had been isolated from Medicago sativa. Throughmorphological, physiological and biochemical detection of16s rDNA, those eightstrains belonged to: Microbacterium sp.; Xanthomonas sp; Arthrobacter sp.;Pseudomonas sp.; Staphylococcus sp. and Pantoea sp..2. Eight isolated endophytic strains were able to synthesize ACC deaminase, IAA,siderophore and phosphate solubilization capacity. All of the8bacteria strains hadACC deaminase synthesis capabilities, the synthesis ACC deaminase ability ofKHY-5and KHY-6were significantly higher than the other strains, others followed:KHY-1>KHY-7>KHY-2>KHY-8>KHY-3> KHY-4. The IAA synthesis ability ofKHY-2and KHY-5were no significant different while on the concentration ofL-Trp500μg/mL, the IAA synthesis ability of KHY-6, KHY-7, KHY-1has asignificant increase; the IAA synthesis ability of KHY-8, KHY-4, KHY-3increasedwith the increasing of L-Trp concentration. Each of the8endophytic strains has theability to synthesize siderophore. Its ability followed in order: KHY-6, KHY-5,KHY-7, KHY-3, KHY-4, KHY-2, KHY-8. In addition, eight endophytic isolateshave phosphate solubilization activity, the strongest was strain KHY-7with valueof324.47μg/mL, the weakest were KHY-1and KHY-6with the value of23.60and23.76μg/mL.3. Eight endopytic strains can promote the growth of alfalfa significantly. The alfalfatreated with endophytic bacteria were significantly better than the control on plant height, shoot fresh weight, root length, fresh weight underground, ground dryweight, dry weight of underground and other physiological indices. All theendophytic strains can promote the growth of alfalfa. In farmland soil experiment,KHY-5and ASL10were the best in promoting alfalfa growth; in saline soilexperiment, above ground growth promoting better for KHY-7, KHY-6and KHY-8followed.4. Experiments results showed that strain KHY-8has a broad-spectrum antimicrobialresistance activity. KHY-8significantly inhibited the wilt effect of alfalfa caused byFusarium oxysporum. The fungal inhibition rate was73.33%against Fusariumoxysporum by KHY-8in the plate experiment; in the plant vivo biocontrolexperiments, the control group is almost all of onset, the disease index reached88.98%. Groups treated with KHY-8showed significant differences compared withthe control group with low incidence rate and mild symptoms. the disease indexwas37.50%, the relative efficacy was57.81%. KHY-8can significantly inhibit thegrowth of Fusarium oxysporum.