Abstract:

In order to explore the microbial resources of saline-alkali tolerance, stress resistance and growth promotion in the cold and arid regions of northern China, and to support the sustainable development of agriculture in saline-alkali land, the stable saline-alkali tolerant composite strains GF-S1, GF-S2 and GF-S3 were used as materials, and the maize variety 'Dika 159' was used as the test crop. The mechanism of stress resistance and growth promotion of composite strains on maize seedlings under saline-alkali stress (soil pH 9.0, total salt content 3.15 g/kg) was investigated by pot experiment. The activities of antioxidant enzymes (CAT, POD, SOD), the contents of osmotic regulatory substances (proline, MDA), plant height, fresh weight and dry weight of maize leaves at different growth stages (7, 14, 21, 28 d) were determined, and the correlation analysis was carried out. The results indicated that under saline-alkali stress, the composite bacterial strain could all enhance the antioxidant enzyme activity of corn leaves, increase the proline content, reduce the malondialdehyde content, and increase the plant height, total fresh weight and total dry weight of corn. Among them, the stress-resistant promoting effect of the composite bacterial strain GF-S3 was the best. On the 28^th day, compared with CK, the antioxidant enzyme activities of GF-S3 increased by 21.85%, 18.64%, and 18.91% respectively, the proline content increased by 18.98%; the malondialdehyde content decreased by 54.24%; the height of the corn plants, the fresh weight of the whole plant, and the dry weight of the whole plant increased by 28.27 cm, 9.39 g, and 9.49 g respectively. The dry weight of the entire corn plant was significantly positively correlated with CAT, POD, SOD, and free proline content (P<0.05), with correlation coefficients of 0.72, 0.73, 0.92, and 0.94 respectively; there was no significant correlation between the malondialdehyde content of corn leaves and these parameters (P>0.05). Under saline-alkali stress, the application of the composite bacterial strain can significantly enhance the stress resistance of corn and promote its growth. Among them, the composite bacterial strain GF-S3 has the best stress resistance promoting effect. This research provides beneficial microbial resources for stress resistance and growth promotion in the saline-alkali resistant areas of northern cold and arid regions.

Key words: maize, salt and alkali stress, saline-alkali tolerant bacteria strain, compound bacterium agent, stress resistance and growth promotion