Controlled environment agriculture will play an important role in feeding the increasing world population as urbanization is expanding, and arable land is decreasing. Higher yields will help offset the initial high cost for building hydroponic production facilities. Beneficial bacterial endophytes have been receiving more attention in sustainable agriculture practices because they can promote plant growth, enhance nutrient uptake, and inhibit pathogen growth. Bok Choy (Brassica rapa subsp. chinensis) is a cruciferous vegetable that's often used in Asian cooking. It is a nutrient-dense vegetable high in fiber, vitamins A, C, K, calcium and vitamin B6. The entire Bok Choy plant is edible, including the leaves, stalks, and flowers. Initially, seven bacterial endophytes from our bacterial endophyte library were chosen to test plant growth promotion in two Bok Choy cultivars (Wan Wan Qing and White Stem) in pots with clay pebble under controlled environmental conditions. The results showed that bacterial endophytes (IALR1786 and IALR1368) significantly increased shoot fresh weight of cv. White Stem by 26.9% and 20.8%, respectively. Bacterial endophytes (IALR1368, IALR1629, IALR1422 and IALR1786) significantly increased shoot fresh weight of cv. Wan Wan Qing by 44.7%, 34.3%, 26.1%, and 22.0%, respectively. Then, the 3 best bacterial endophytes (IALR1368, IALR1629, and IALR1786) were chosen to further test in pots with clay pebble, as well as in nutrient film technique (NFT) units. In pots with clay pebble, IALR1629 increased shoot fresh weight of cv. White Stem by 13.5% but not significantly. IALR1786 significantly increased root fresh weight of cv. White Stem by 25.9%. Similar results were obtained in cv. Wan Wan Qing. In NFT units, IALR1786 significantly increased shoot fresh weight and root dry weight of cv. White Stem by 23.3% and 33.3%, respectively. All 3 bacterial endophytes significantly increased shoot fresh weight of cv. Wan Wan Qing by from 19.1% to 41.8%. IALR1786 also significantly enhanced root dry weight of cv. Wan Wan Qing by 30.8%. These bacterial endophytes will be identified using 16S sequencing and tested with other cultivars. In Summary, IALR1786 performs best and consistently achieves growth promotion in two different cultivars under different conditions.
