Role of Dominant Phyllosphere Bacteria with Plant Growth–Promoting Characteristics on Growth and Nutrition of Maize (Zea mays L.)

Plant growth–promoting bacteria (PGPB) inhabiting the phyllosphere improve the growth and yield of plants by producing natural growth regulators. The objectives of this study were to identify and characterize the indigenous PGPB of maize phyllosphere and to evaluate their ability to improve growth and nutritional status of maize (Zea mays L.). The bacteria were isolated from phyllosphere of maize in the fields located at different geographical locations and screened for various plant growth–promoting (PGP) traits. The most promising PGPB were identified by 16S rRNA gene sequence analysis. A greenhouse experiment was carried out in a completely randomized design with the foliar application of 15 different bacterial treatments. It was found that members of genera Bacillus, Pseudomonas, Microbacterium, Stenotrophomonas, Enterobacter, Pseudarthrobacter, and Kocuria were the most dominant PGPB in maize phyllosphere. Foliar spray of M. arborescens, B. subtilis + S. maltophilia, S. maltophilia, B. megaterium, and E. hormaechei significantly increased the shoot dry weight by 10.40, 9.53, 8.86, 8.73, and 6.00% compared with the control, respectively. M. arborescens and S. maltophilia isolates with the ability to produce indole-3-acetic acid (IAA) had positive effects on dry weight of the shoot. E. hormaechei showed a marked nitrogenase activity, phosphate solubilization, and IAA production and was the most effective treatment in improving the uptake of most nutrients. The nitrogenase activity and IAA production were generally considered to be the most important PGP traits of the bacteria when applied via foliar spray. Overall, the findings presented in this study indicate that the foliar application of the leaf-colonizing PGPB enhanced the growth and nutritional status of maize.