Antagonistic Endophytic Bacteria Diversity In Garlic And Their Growth-promoting Characteristics

174 endophytic bacterial strains were isolated from health garlic in three different sites by the concentration gradient method. Through antagonistic experiments, we obtained 62 endophytic bacterial strains, which have better effect on against 4 pathogenic fungi, including Magnaporthe grisea , Fusarium oxysporum f. sp. Cucumerinum , Colletotrichum gloeosporioides and Valsa mali Miyabe et Yamada. Combined the analysis of ERIC-PCR and PCR-RFLP from 16S rDNA of bacterial with the enzyme type, the built tree plot was constructed based on the cluster analysis with the Unweighted Pair Group Mathematical Average (UPGMA) MVSP3.1. According to the results of cluster analysis, we constructed phylogenetic tree by 11 selected strains with the sequence analysis of their 16S rDNA. The results showed that the 62 tested strains were from eight different genuses, including Ochrobactrum,Novosphingobium,Brevundimonas,Pseudomonas, Serratia,Rhodococcus,Arthrobacter and Bacillus. 62 tested strains from different sites showed significant differences in biodiversity. Strains obtained from Jinxiang were from three genuses, which were respectively Arthrobacter, Serratia and Bacillus. Bacillus was the dominant genus, and accounted for 84.2% of total strains separated in the site; Strains obtained from Qixian were from six genuses, which were Pseudomonas, Rhodococcus, Ochrobactrum, Arthrobacter, Serratia and Bacillus. Bacillus was also the dominant genus, and accounted for 47.6% of total strains separated in the site; Strains obtained from Shexian were from eight genuses: Pseudomonas, Rhodococcus, Ochrobactrum, Arthrobacter, Brevundimonas, Serratia, Bacillus and Novosphingobium.Among Ochrobactrum accounted for 22.8%,Arthrobacter accounted for 18.2%,and Serratia accounted for 18.2% of total strains separated in the site. Overall Pseudomonas was the most common genus in endophytic bacterial from garlic. The result was consistent with report.All the endophytic bacterias isolated in this study had been reported in literatures, and some strains even had a more in-depth study, such as Ochrobactrum, Novosphingobium, Brevundimonas, Serratia, Rhodococcus and Arthrobacter nicotinovorans et al.But these bacterias were all isolated from soil and water before. In this study, we obtainded these endophytic bacteria in garlic, which itself has a strong inhibitory activity, and furthermore we studied their biodiversity. The research in this area was the first time. On the whole, the strains obtaind from different sites showed different diversity in genus and amount.The strains from different sites and different variants showed obvious differences on their biodiversity.We also tested that all the 62 strains have the capacity on produce acetic acid (IAA), the highest content of IAA, which be produced by one strain, is about 49.664μg.mL-1. Likewise, we also found that the content of IAA have reached 20μg/mL, produced by 5 strains, from all the strains. And above 82.3 %( 51 strains) strains belonged to eight different genuses but except Arthrobacter sulfureus could produce siderophore.Moreover, 33.87%(21 strains) strains could dissolve organic phosphorus and the range of D/d was from 1.13 to 1.85. 21 strains are attributed to Ochrobactrum(4 strains),Pseudomonas(4 strains),Serratia(7 strains),Arthrobacter nicotinovorans(1 strain),Bacillus subtilis(2 strains)and Bacillus thuringiensis(4 strains);all remaining strains belonged to Novosphingobium, Brevundimonas, Rhodococcus and Arthrobacter sulfureus could not dissolve organic phosphorus. And all tested strains (62strains) could not dissolve Inorganic phosphorus.From the results of 62 tested strains producing IAA, siderophores and phosphate solubilization, we could see that some strains belong to Ochrobactrum, Rhodococcus and Bacillus and all strains belong to Serratia could produce higher levels of IAA. Meanwhile strains from Novosphingobium,Brevundimonas,Pseudomonas and Arthrobacter had a lower ability to produce IAA.82.3% (51) strains were distributed eight different genuses could produce siderophore.The results showed that the antagonistic inhibition mechanism of the majority of selected strains is likely due to the production of siderophore .We also could see that Arthrobacter sulfurous was different from Arthrobacter nicotinovorans in ability to produce siderophore, and strains belonged to Arthrobacter sulfurous could produce siderophore,in contrast strains belong to Arthrobacter nicotinovorans could not. All tested strains could not dissolve inorganic phosphorus and showed different ability in dissolving organic phosphorus. Some strains belonged to Arthrobacter or Bacillus and all strains belonged to Serratia or Pseudomonas had the ability of dissolving organic phosphorus; But all srains belonged to Rhodococcus could not.Combined the capacity of the strains, including antifungal activity, IAA production, siderophore production and the organic phosphorus dissolutions, we selected 6 better strains and numbered them as DSQ5, DSS21, DSQ4, DSJ9, DSJ3 and DSS10.The acquisition of these strains could be a foundation on the develop new Biopesticides from the endophytic bacteria of garlic later.