Analysis of the PGPB potential of bacterial endophytes associated with maize

Abstract

Bacterial endophytes live inside plants for at least part of their life cycle, because plants are very attractive as nutrient reservoirs for such bacteria. Plants need the presence of those associated bacteria for their growth and adaptation to different ecosystems. This is the case of maize, which is a well-known cereal crop for hosting a great diversity of endophytic bacteria. Thus, microbes take advantage of the plant nutrients, whereas plants receive benefits from associated bacteria, such as nitrogen and phosphorous uptake. To study bacterial diversity, we isolated the endophytic bacteria from stalk and root of maize plants (Zea mays) growing in a soil of Ciudad Rodrigo (NW Spain). Bacterial isolates were analyzed by RAPD fingerprinting, allowing the differentiation among strains of the same species. Our results showed the high diversity of isolates inside maize rhizosphere and endosphere, establishing many different RAPD types. However, despite the usefulness of RAPD profiles in bacterial diversity analysis, 16S rRNA gene sequencing was carried out and subsequently analyzed. A total of 25 different genera were isolated. Moreover, we determined the ability of these strains to promote plant growth, performing in vitro PGPB mechanism analysis: (i) phosphate solubilization, (ii) siderophores production, and (iii) IAA and/or precursors biosynthesis. Here, we report the infraspecific diversity of bacterial endophytes isolated from Z. mays, which is higher than we expected. Moreover, the analysis of in vitro PGPB mechanisms indicates that these strains can promote plant development, suggesting their possible application in biofertilization schemes.