Isolation, Identification, Colonization And Characteristics Of Endophytic Bacteria With Antagonism Against Plant Pathogenic Fungi From Rice

Endophytic bacteria are defined as bacteria detected inside surface-sterilized plant tissues or extracted from internal plant tissues and having no visibly harmful effects on the plants. It has been reported that the endophytic bacteria has been isolated from various parts of rice. And the biological control of plant pathogens using endophytic bacteria exhibiting anti-pathogen activity has been examined for rice plants as well as other plants. In this study, we isolated and identified endophytic bacteria from rice seedlings, and detected their antagonism against plant pathogenic fungi. The application of endophytic bacteria with inhibitory activity against pathogens to agriculture and as vectors for anti-insect genes for the control of pests in crops has been a long-standing goal.1. In this study, Sixty-three and twenty-six endophytic bacteria were acquired from rice seedlings and its roots, respectively. In vitro screening of the isolates for antagonistic activity against phytopathogenic fungi, Rhizoctonia solani, Dothiorella gregaria, Fusarium oxysporium, and Fusarium graminearum, the results showed that all the twenty-seven strains were antagonistic against different phytopathogenic fungi. The confrontation assay also showed that five endophytic Bacillus spp. had better antagonism against nine different phytopathogenic fungi.2. The inhibition rate of endophytic bacteria against phytopathogenic fungi was calculated. Five Bacillus sps. strains were noted for their effective antagonistism against nine different phytopathogenic fungi, with inhibition rates ranging between 28.1% and 62.5%. The SDG-26 strain had an inhibition rate of 62.5% against Rhizoctonia solani which was recorded as the highest.3. The colonization of the five endophytes in rice was carried out using the irrigation inoculation method. The target strains were then harvested from the rice tissues. The bacteria population initially showed a downward trend and later increased gradually. The results showed that the strains were endophytes in rice and could subsist, reproduction and transfer in rice tissues, and also that the detection of colonization of rice endophytic bacteria can be feasibly labeled with rifampicin resistance.4. All the isolates were screened for antagonistic activity against phytopathogenic fungi. Only five rice endophytic Bacillus spp. have effective antagonism against nine different phytopathogenic fungi (numbered as SDG-26、SDG-201、SDG-203、SDG-31、SDG-202). They were aerobic, Gram-positive and spore-forming rod bacteria. Based on their 16S rRNA gene sequence analysis and also their physiological and biochemical characteristics, the starins were preliminarily identified as follows:strains SDG-31 and SDG-26 were identified as species of Bacillus amyloliquetaciens, strains SDG-201 and SDG-203 were regarded as Bacillus subtilis, and strain SDG-202 was regarded as Bacillus sp.