Alternative Mechanism for the Evaluation of Indole-3-Acetic Acid (IAA) Production by Azospirillum brasilense Strains and Its Effects on the Germination and Growth of Maize Seedlings

OSCAR MASCIARELLI; LUCIA URBANI; HERMINDA REINOSO; VIRGINIA LUNA

JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY

KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY

Lugar: Seul; Año: 2013

1017-7825

We evaluated the production of indole-3-acetic acid (IAA)by Azospirillum brasilense strains in vitro (cell culture supernatants)and in vivo (stems and roots of maize seedlings)to clarify the role of this phytohormone as a signalingand effector molecule in the symbiotic interaction betweenmaize and A. brasilense. The three strains all showed IAAproduction when cultured in NFb medium supplementedwith 100 μg/ml L-tryptophan. The level of IAA productionwas 41.5 μg/ml for Yu62, 12.9 μg/ml for Az39, and 0.15μg/ml for ipdC-. The release of IAA into culture medium bythe bacteria appeared to be the main activator of the earlygrowth promotion observed in the inoculated maize seedlings.The application of supernatants with different IAAcontents caused significant differences in the seedling growth.This observation provides the basis for novel technologicaltools for effective quality control procedures on inoculants.The approach described can be incorporated into differentinoculation methods, including line sowing, downspout, andfoliar techniques, and increase the sustainability of symbioticplant-bacteria systems.