Identification and study of endophytic bacteria in the model plant Medicago truncatula

Abstract

In this study, the effects of endophytes on the Medicago-Sinorhizobium symbiosis and the interaction between Medicago and endophyte bacteria were studied. For this, soil from organic farms or the desert was used to create a collection of endophytic bacterial strains. The capacity of 46 of them to infect Medicago R108 and A17 roots under axenic conditions was investigated. Five strains (M17, M18, M50, M67.2 and BT-37) among the forty validated bacteria were selected for molecular identification .We studied the potential effects of the PGPR of the strain studied, the analysis of the response of Medicago to salt stress in the presence or in the absence of endophytes was evaluated. The results indicate the presence of various effects of the tested strain on the protection of Medicago against abiotic stress. Interestingly, the less infectious strain may possess the highest protection against salt stress. the qPCR analysis of the PR10, PR5 and NDR1-Like genes after inoculation of the A17 ecotype by the endophytes showed Different levels of immune stimulation are observed depending on the strain used. Interestingly, the expressions of the PR10 genes are correlated with the level of tissue occupancy by endophytes .Finally, we have studied the impact of endophytes on the Medicago-Sinorhizobium symbiosis, a co-inoculation of Medicago with the strain studied and the rhizobium was carried out. Our preliminary data suggest that endophytes have a weak impact on the initiation of the symbiotic interaction. endophytes tested are able to infect nodules and reduce nitrogen-fixing capacity. Interestingly, Lysinibaccillus sp. These show the lowest root colonization ability, display the highest nodule infection rates. This observation underlies the difference between nodule and roots and could be explained by the difference in immunity and/or metabolic status. Finally we were able to demonstrate that infection rates do not seem to be correlated with nitrogen fixation.