Dynamics and characterization of the endophytic community of Melia azedarach trees infected with phytoplasmas

LÓPEZ-GASTÓN MM; CARDOZO MARINA; NAMTZ YAEL; GALDEANO E; COLLAVINO M.M

Viena

Congreso; Simposio Internacional Micrope 2017; 2017

Micrope

We studied Melia azedarach endophytic community considering the effect of phytoplasma infection, plantorgan and sampling season on a two year-survey, and analyzed in vitro plant growth promoting activities.403 isolates were characterized by Rep-PCR and 16S rDNA. Community diversity was affected by organsource, but not by season or infection status. Diversity was higher in root samples, being the most representedorders Bacillales (31%), Burkholderiales (30%), Rhizobiales (17%) and Pseudomonadales (13%).Enterobacteriales were present only in leaf samples, and Burkholderiales only in root ones. Within root isolates,the proportion of Burkholderiales and Rhizobiales was higher during the autumn season while Bacillales andEnterobacteriales increased during the spring. Leaf community was affected by phytoplasma infection sinceBacillales and Enterobacteriales were found in higher proportion in infected leaves.N fixation, P solubilization, indol acetic acid (IAA) production, ACC deaminase activity, siderophore andantibiotic production were assayed. Bacillus and Burkholderia isolates had the highest functional diversity.Isolates from Bacillus, Pseudomonas, Enterobacter, Burkholderia and Paenibacillus grew on Nfb medium andwere positive for nifH gene PCR amplification. 97% of the isolates had P solubilizing activity, beingPseudomonas and Kosakonia highly efficient. 50 isolates showed IAA production, 3 from Enterobacter,Pseudomonas and Bacillus produced twice the reference strain Azospirillum brasiliensis. 38 isolates producedsiderophores and 16 had acc deaminase activity. In both activities, most of the positive isolates correspondedto order Burkholderiales and showed considerably higher production than the control strain (Pseudomonasputida). 15 of the 23 Pseudomonas isolates were PCR positive for genes (phl, prn, phz, and plt) related toantibiosis activity while only one Bacillus isolate showed amplification of zma gene (zwitermycin).In conclusion, M. azedarach root and leaf endophytic communities are different in structure, diversity andcomposition as well as in their response to phytoplasma infection and seasonal conditions. Besides, they havehigh PGPB potential as reflected by their diverse and efficient functional activities. Selected isolates ofBurkholderia, Bacillus and Pseudomonas are being tested now for their growth promoting activities afterplantlet inoculation.