Isolation,Identification Of Bacterial Endophytes From Maize Plants And Their Applications For Growth Promotion,Disease Control And Yield Enhancement

Bacterial endophytes are important microbial resources. Many endophytic bacterial species produce phytohormones, and have phosphorous-solubilizing and nitrogen-fixing activities. They can significantly promote plant growth, and enhance stress resistance and yields on host plants. The bacterial endophytes thus have a great potential for reducing the use of chemical fertilizers and pesticides as well as enhancing stress resistance and yields on related crops. In the recent years, researchers pay high attention to the endophytes in maize plants. The isolation and application of the endophytic microbes become a hot area of research. To explore effective bacterial endophytes for disease control, healthy corn plants at different growth stages were sampled from Nanyang city, Henan province. A total of 39 bacterial endophytes were isolated from surface-sterilized corn tissues using a routine tissue isolation method. In the present study, growth promotion capacity of the bacterial endophytes based on pot culture was used as an initial screening parameter for selection of biocontrol agents against southern corn rust. Higher growth-promoting strains were screened out by pot cultivation method from the bacterial endophytes isolated. The five strains (L-2, R-4, R-8, R-14 and S3) with higher growth-promoting activities were identified as members of Bacillus based on their 16S rDNA sequences. Based on combined tests including pot culture, phosphorus-solubilizing and nitrogen-fixing activities, strain R-4 was selected as a test biocontrol agent with high growth promoting capacity. The strain R-4 was further identified as Bacillus cereus based on its morphological, biochemical and physiological characteristics as well as 16S rDNA sequence. The optimal temperature and pH for growth of strain R-4 were 30? and 8, respectively. Three corn cultivars (Xianyu-335, Jundan-20 and Yinnuo-1) were separately treated by strain R-4, and sown in the field. The efficacies of strain R-4 in controlling southern corn rust and enhancing yields on the three cultivars were evaluated in the field. The mean efficacies of strains R-4 in controlling southern corn rust was 32.4% with an mean enhanced yield of 30 kg per 667.7 m2. The results indicated a potential application perspective of the strain for biocontrol of southern corn rust in corn production. The phosphorous-solubilizing and nitrogen-fixing capacities of strain R-4 might be considered as an important mechanism for the growth promotion and yield enhancement. In spite of the mechanism(s) on disease suppression by strain R-4 remains to be further studied in detail, healthy growth of a maize plant might contribute to disease suppression.