Abstract
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 the 16S ribosomal gene. The main indole acetic acid producers wereEnterobactersp. IP11,Enterobactersp. IP14, andE. asburiaeIP24.Achromobacter spaniusIP23 presented the highest levels of cellulolytic activity and potassium solubilization.Bacillus thuringiensisIP21 andStaphylococcus saprophyticusIJ8 showed the highest levels of fixed nitrogen. The levels of calcium phosphate and aluminum phosphate inB. thuringiensisIP21 were notable, as this strain solubilized 481.00 and 39.33 mg of phosphorus mL−1, respectively; however, for Araxá apatite, the results forB. anthracisIP17 were notable (622.99 mg phosphorus mL−1), while for iron phosphate solubilization,Enterobactersp. IP14, which solubilized 105.66 mg phosphorus mL−1was notable. TheB. thuringiensisIP21 andEnterobactersp. IP11 isolates 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, plants inoculated withEnterobactersp. IP14,B. anthracisIP17, andA. spaniusIP23 presented higher values than the controls. Furthermore, plants inoculated withB. thuringiensisIP21 presented higher root dry matter and total dry matter values, and those inoculated withEnterobactersp. IP14 also presented higher total dry matter values. 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.
Highlights
Sugarcane (Saccharum officinarum L.) is one of the most economically important agricultural crop species, mainly as a source of sugar, and is grown worldwide in tropical and subtropical areas
Sixty bacterial strains were isolated from the rhizospheres of the sugarcane plant varieties IAC95-5000 and RB86-7515 in the municipality of Jaboticabal-SP; 62 colonies were obtained from the rhizospheres of the varieties CTC9 and RB85-5156 in the municipality of Frutal-MG; and 45 colonies were isolated from the rhizospheres of the varieties IAC91-1099 and CTC4 in the municipality of Pirajuba-MG
Cellulolytic Activity The highest cellulolytic activity was observed for A. spanius (0.61 U mL−1), S. saprophyticus (0.58 U mL−1), Enterobacter 1 (0.58 U mL−1), B. anthracis (0.57 U mL−1), and B. thuringiensis (0.56 U mL−1)
Summary
Sugarcane (Saccharum officinarum L.) is one of the most economically important agricultural crop species, mainly as a source of sugar, and is grown worldwide in tropical and subtropical areas. An alternative to fertilizers that can reduce costs and environmental impacts is the use of plant growth-promoting rhizobacteria (PGPRs) (Pérez-Montaño et al, 2014). This group of bacteria inhabits the plant rhizosphere and promotes plant growth (Zhou et al, 2016; Riaz et al, 2021). A wide range of applications of these beneficial rhizobacteria in sugarcane crops have been proposed, and a considerable number of research studies have focused on their functionality and applicability. The results of several studies have shown that the utilization of PGPRs in sugarcane is a great alternative to the challenges of modern agriculture (dos Santos et al, 2020)
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