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.
Aims: The present study aimed at gaining an insight into the abundance and genetic diversity of culturable N-fixing epiphyte bacteria on the phyllosphere of maize in arid and semi-arid regions of Iran. Methods and Results: Leaf samples of the maize variety, 'single cross 704' (Zea mays L.) were collected from different locations in Iran. The community of culturable N-fixing epiphyte bacteria present was examined by 16S rRNA sequencing, BOXAIR-polymerase chain reaction (PCR) and restricted fragment length polymorphisms analysis of 16S rRNA gene (16S-RFLP). Approximately, 31Á82% of the 242 isolates were identified as N-fixers by cultivation of bacteria in Rennie medium and detection of their nifH gene. The N-fixers were affiliated with four bacterial phyla: Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. 16S rRNA sequencing detected 16 genera and 24 different species in the identified phyla. The most dominant genus was Bacillus and the species identified were B. pumilus, B. amyloliquefaciens, B. subtilis, B. paralicheniformis, B. licheniformis, B. niabensis and B. megaterium. In total, 22 RFLP groups were present among the isolates originally identified as N-fixing bacteria. BOXAIR-PCR showed that there was a low similarity level among the N-fixing bacteria isolates, and genetic differentiation of individual strains was relatively great. Conclusions: Our findings suggest that nitrogen-fixing epiphyte bacteria on the phyllosphere of maize may provide significant nitrogen input into arid and semi-arid ecosystem. Significance and Impact of the Study: This research implies that phyllosphere epiphyte diazotrophs have much to offer in sustainable agriculture and can be an alternative to chemical N-fertilizers for providing nitrogen to crops arid and semi-arid regions.
Purpose Using different organic beds to produce vermicompost may influence on quality of vermicompost and its derived productions. Methods A greenhouse experiment was conducted to compare the properties of vermicompost, vermiwash and vermicompost tea obtained from three types of organic beds consisted of cow manure, leaf meal and a combination of cow manure and leaf meal (1:1 w/w). Results Cow manure vermicompost had more desirable effect on many measured traits toward leaf meal and combination of leaf meal and cow manure vermicomposts. Vermicompost tea obtained from three vermicompost types was richer in terms of macro and micro nutrients, C/N, percent of organic matter and organic carbon toward the vermiwash produced from the same vermicompost. Vermiwash and vermicompost tea produced from cow manure vermicompost were at first order in majority of measured traits toward others. Conclusions Generally vermicompost which was richer in nutrient concentrations affected intensively quality of vermiwash and vermicompost tea produced from it.
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