Growth-Promoting Potential of Rhizobacteria Isolated From Sugarcane

The search for plant growth-promoting rhizobacteria (PGPRs) addresses the ongoing need for new bioinoculants to be used on various agricultural crop species, including sugarcane. Bacterial strains were isolated from the rhizosphere of sugarcane plants and identified by sequencing of the 16S ribosomal gene. The main indole acetic acid producers were Enterobacter sp. IP11, Enterobacter sp. IP14 and E. asburiae IP24. A. spanius IP23 presented the highest levels of cellulolytic activity and potassium solubilization. B. thuringiensis IP21 and S. saprophyticus IJ8 showed the highest levels of fixed nitrogen. The levels of calcium phosphate and aluminum phosphate in B. thuringiensis IP21 were notable, as it solubilized 481.00 and 39.33 mg of phosphorus mL-1, respectively; however, for Araxa apatite, the results for B. anthracis IP17 were notable, while for iron phosphate solubilization, Enterobacter sp. IP14, which solubilized 622.99 and 105.66 mg phosphorus mL-1, respectively, were notable. B. thuringiensis IP21 and Enterobacter sp. IP11 isolate promoted the growth of the tallest sugarcane plants, inducing increases of 14.1 and 10.4% relative to the control plants, respectively. For shoot dry matter, root dry matter, and total dry matter, Enterobacter sp. IP14, B. anthracis IP17, and A. spanius IP23 presented higher values than the controls. Furthermore, B. thuringiensis IP21 presented higher root dry matter and total dry matter and Enterobacter sp. IP14 isolate also presented higher total dry matter. These results indicate that bacteria with the potential for use as future inoculants should be investigated since bacteria with plant growth-related characteristics may not impact growth promotion.