Abstract
The genus Gluconacetobacter comprises different species with agricultural and industrial importance. This study aims at determining the presence of Gluconacetobacter diazotrophicus and Gluconacetobacter sacchari in sugarcane and tomato crops considering their potential biotechnological applications. Bacteria were isolated from roots, stems and leaf tissues and identified using phenotypic and biochemical evaluations, and molecular and phylogenetic analyses. Isolates were characterized by the production of indolic compounds, nitrogenase activity and phosphate solubilization. For this, G. diazotrophicus ATCC 49037 was used as the reference strain. The results showed that all isolates of native G. diazotrophicus exhibited equal or better phosphate solubilization index (SI) for CaCO3 and AlPO4 than reference strain. For G. sacchari, GIBI031 isolate displayed better SI for both phosphate sources and GIBI014 isolate had better SI only for AlPO4. G. diazotrophicus GIBI029 had a greater production of indolic compounds than ATCC 49037 strain in the presence of tryptophan. All isolates except G sacchari GIBI031, showed better nitrogenase activity than the control. These results constitute the first report confirming the presence of G. diazotrophicus and G. sacchari associated with sugarcane in Colombia. In addition, this is the first report on the presence of G. sacchari in tomato under natural conditions. Finally, one G. sacchari isolate presented nitrogenase activity despite the fact that this is a differential characteristic between G. diazotrophicus and G. sacchari. These findings have ecological significance and will advance research towards the evaluation of plant-soil interactions involving these bacteria in crops other than sugarcane. The isolates found are potential candidates for the development of novel biotechnological processes for production of new alternative biofertilizers considering the significant plant-growth promotion properties determined in this work. Key words: Sugarcane, tomato, Gluconacetobacter diazotrophicus, Gluconacetobacter sacchari, indolic compounds, phosphate solubilization, nitrogenase activity.
Highlights
The increase of world population has led to the excessive use of chemical fertilizers causing soil erosion and loss of its physicochemical and microbiological equilibria provoking negative environmental impacts (White and Brown, 2010)
The two G. diazotrophicus isolates from sugarcane were obtained from root and stem samples with a BLAST identity (BI) of 99.37% in both cases and global alignment identity (GI) of 98.42 and 98.24%, respectively
Two of the three G. sacchari isolates were recovered from sugarcane: GIBI014 (BI 100% and GI 98.78%) and GIBI031 (BI 100% and GI 98.95%); the third isolate was recovered from tomato and coded as GIBI141 (BI 99.83% and GI 99.65%)
Summary
The increase of world population has led to the excessive use of chemical fertilizers causing soil erosion and loss of its physicochemical and microbiological equilibria provoking negative environmental impacts (White and Brown, 2010) For these reasons, the need to produce alternative environmentally friendly agricultural supplies contributing to enhance the crop yield to meet the global food demand has arisen. The auxins are a group of phytohormones regulating the plant development and having a direct effect on the growth, cell division, and formation of the roots. They are applied during the in vitro cultivation of plant material and in plantations (Castillo et al, 2005)
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