Isolates of Bacillus sp. from garlic: effect on corn development and plant growth-promoting mechanisms

ABSTRACT

Corn and garlic are important crops to Curitibanos region (state of Santa Catarina – Brazil), often planted in alternate cropping seasons. Production costs are high, especially due to N fertilizer, since they are highly demanding in N. In addition to reducing economic costs, the search for environmentally sustainable technologies has stimulated the study of interactions between plants and growth-promoting microorganisms. Rhizobacteria, e.g., Bacillus sp., have been presenting as growth-promoting microorganisms. Five isolates of garlic rhizosphere from 27 individuals of the Plant Growth Promoting Microorganisms group collection were tested on corn under field conditions, comparing to two levels of nitrogen fertilization: 120 and 60 kg ha^-1. The Bacillus collection was also evaluated in vitro for phosphate solubilization, production of IAA (Indole Acetic Acid), extracellular enzymes, and inhibition of Sclerotium cepivorum. For plant height and stalk diameter, the inoculation of the EB16 isolate showed similar results to the fertilization with 120 and 60 kg ha^-1 of N in corn. Both EB16 and EB02 isolates increased corn ear diameter and the yield was similar to that observed in the treatment with 60 kg ha^-1 of N, indicating their potential as growth-promoters. All strains of the collection produced IAA, and most of them solubilized calcium phosphate and produced lipases and urease. Forty-eight percent of the isolates inhibited S. cepivorum. The EB01, EB15, EB17, and EB27 were positive for three of the four mechanisms analyzed. During these evaluations, it was observed that EB02 and EB16 produced equivalent amounts of IAA, suggesting that more than one growth-promoting mechanism is involved in the efficiency of corn development induction.

rhizobacteria; Zea mays L; merril; Allium sativum; growth-promoters