Enhanced Tolerance of Chinese Cabbage Seedlings Mediated by H26-2 and H30-3 against High Temperature Stress and Fungal Infections.

Two rhizobacteria H26-2 and H30-3 were evaluated whether they are involved in stress tolerance against drought and high temperature as well as fungal infections in Chinese cabbage plants. Chinese cabbage seedlings cv. Ryeokgwang (spring cultivar) has shown better growth compared to cv. Buram-3-ho (autumn cultivar) under high temperature conditions in a greenhouse, whilst there was no difference in drought stress tolerance of the two cultivars. growth of H26-2 and H30-3 were differentially regulated under PEG 6000-induced drought stress at different growing temperatures (30, 40 and 50°C). Pretreatment with H26-2 and H30-3 enhanced the tolerance of Chinese cabbage seedlings to high temperature, but not to drought stress. It turns out that only H30-3 showed antifungal activities and crop protection against two fungal pathogens and causing black spots and anthracnose on Chinese cabbage plants cv. Ryeokgwang, respectively. H30-3 brings several genes involved in production of cyclic lipopeptides in its genome and secreted hydrolytic enzymes like chitinase, protease and cellulase. H30-3 was found to produce siderophore, a high affinity iron-chelating compound. Expressions of and genes were up-regulated in Chinese cabbage leaves by H30-3. These findings suggest that integration of H26-2 and H30-3 in Chinese cabbage production system may increase productivity through improved plant growth under high temperature and crop protection against fungal pathogens.