Isolation of Potent Endophytic Bacteria Able to Boost Plant Growth and Control Pathogens.

Abstract

Endophytic bacteria are promising source of plant probiotics due to their ability to promote plant growth and control pathogens. This study aims to isolate diverse endophytic bacteria capable of boosting plant growth and controlling pathogens. A total of 62 endophytic bacteria were isolated from the stems, leaves and roots of the flowering plant ( Matthiola incana ) , the potato plant ( Solanum tuberosum ) , the Prickly pear plant ( Opuntia-ficus indica ) , and seedlings of Acacia sp. trees. Endophytic bacterial isolates were screened for their production of indole acetic acid (IAA) and cellulase enzyme, as well as their antagonistic activities against potato pathogens such as Ralstonia solanacearum and Fusarium oxysporum . The most promising endophytic isolates ML7 and PL10 showed the highest productivity of IAA, 69.1 and 64.8 µg/ml respectively. They also exhibited high cellulase activities on Congo red plates showing clear zone/colony diameters ratios of 3.36 and 2.8 respectively. The antagonistic activities of ML7 and PL10 against R. solanacearum were represented as 6 and 16 mm inhibition zones diameters, while the inhibition zones diameters representing the antagonistic activities of ML7 and PL10 against F. oxysporum were 58 and 7 mm , respectively. Isolates ML7 and PL10 exhibited a good ability to survive in a broad range of temperatures from 15 to 45 °C and upon exposure to direct UV radiation for 3 hours. Finally, isolates ML7 and PL10 were identified as Achromobacter marplatensis and Bacillus velezensis , respectively. Therefore, it is highly recommended that they can be used as plant probiotics in future field studies.