Native Plant Growth-Promoting Rhizobacteria for Growth Promotion of Lettuce from Qassim, Saudi Arabia

<b>Background and Objective:</b> Plant Growth-Promoting Rhizobacteria (PGPR) are a group of bacteria that colonize plant roots and enhance the growth and productivity of plants. However, only those PGPR that is acclimatized to the local soil conditions performs well. The present study aims to pick up effective PGPR isolates from local soil and utilize them as potential bio-inoculants to enhance lettuce plant growth. <b>Materials and Methods:</b> Rhizospheric soil samples were obtained from each of six desert plant species in the Qassim region and 45 bacterial isolates were obtained. Four of them were identified and tested for growth-promoting activities by application to the soil in which lettuce was grown under greenhouse conditions. <b>Results:</b> The selected bacterial isolates were identified as <i>Bacillus cereus</i> BW-201B, <i>Pseudomonas aeruginosa</i> AMU1, <i>Pseudomonas putida</i> CNE30 and <i>Enterobacter</i> sp. CZGRY7. Application of these four isolates to the soil in which lettuce was grown under greenhouse conditions resulted in significant increases in shoot height, shoot weight, chlorophyll levels and the percentages of N, P and K compared with those of control treatment. <b>Conclusion:</b> These findings suggest that local soil bacterial strains represent excellent bioinoculants for growth and yield increase in lettuce under local agro-climatic conditions in Saudi Arabia. Our approach might offer a good alternative for the chemical-free farming of lettuce.