AUTHOR=Kifle Medhin H. , Laing Mark D. 

TITLE=Isolation and Screening of Bacteria for Their Diazotrophic Potential and Their Influence on Growth Promotion of Maize Seedlings in Greenhouses

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.01225

DOI=10.3389/fpls.2015.01225

ISSN=1664-462X

ABSTRACT=<p>Poor soil fertility is one of the major constraints for crop production. Nitrogen is the most limiting nutrient for increasing crop productivity. Therefore, there is a need to identify diazotrophic inoculants as an alternative or supplement to N-fertilizers for sustainable agriculture. In the current study, a number of free-living diazotrophic bacteria were isolated from soils collected from maize rhizosphere and from leaves and roots of maize within the KwaZulu-Natal Province, Republic of South Africa. Ninety-two isolates were selected for further screening because they were able to grow on N-free media containing different carbon sources. Isolates that were very slow to grow on N-free media were discarded. The isolates were screened <italic>in vitro</italic> for diazotrophic potential tests for ammonia production and acetylene reduction. Ethylene (C<sub>2</sub>H<sub>4</sub>) production was quantified and ranged from 4 to 73 nmoles of C<sub>2</sub>H<sub>4</sub>h<sup>−1</sup> culture<sup>−1</sup>. The top 20 isolates were re-screened on maize seedlings, and eight isolates significantly (<italic>P</italic> = 0.001) enhanced some growth parameters of maize above the un-inoculated control. Isolates that showed significant effect on at least two growth parameters were identified at species or genera level. In conclusion, selected diazotrophic isolates may be potentially beneficial but they should be tested more in greenhouse and field conditions with maize to confirm their potential for application as biofertilizers.</p>