Rhizobacterial inoculation to improve the responses of olive cultivars to drought stress

Tunisia is known as an underprivileged country in water resources, and water scarcity is evident in certain regions. In the long term, this situation could become more exacerbated, considering the increased risk of aridity. In this context, this work was carried out to study and compare the ecophysiological behavior of five olive cultivars facing drought stress and to evaluate the contribution of rhizobacteria to mitigate the effects of drought stress on these cultivars. The results showed a significant decrease in the relative water content (RWC) with the lowest percentage recorded for the 'Jarboui' cultivar (RWC = 37%), and the highest percentage was registered for the 'Chemcheli' cultivar (RWC = 71%). In addition, the performance index (PI) decreased for all the five cultivars and it reached the lowest values for 'Jarboui' and 'Chetoui' with 1.51 and 1.57, respectively. For the SPAD index, a decrease was registered for all the cultivars, except 'Chemcheli' (SPAD index = 89). Furthermore, the bacterial inoculation treatment improved the responses of cultivars to water stress. In fact, for all of the studied parameters, it was found that rhizobacterial inoculation significantly attenuated the effects of drought stress with variability dependent on the level of tolerance of the tested cultivars. This response improvement was noted especially in susceptible cultivars like 'Chetoui' and 'Jarboui'.