ABSTRACT
In an attempt to obtain biological control agents for fusariose wilt, a total of 54 endophytic bacterial strains were isolated from the root of plants Urtica dioica and screened for in vitro antagonist activity against Fusarium oxysporum. Among the 54 bacterial isolates, 27 isolates exhibited more than 60% inhibition of mycelia growth of Fusarium oxysporum. The strain R19 which exhibited the most obvious antagonistic activity was selected for greenhouse studies. The SR19 had no pathogenicity and was identified as Paenibacillus polymyxa based on its phenotypical and biochemical properties as well as its 16S rRNA gene sequence. Growth chamber studies resulted in statistically significant increases in inoculating tomato seedling with the endophytic strain SR19 which in turn resulted in improving plant seedling stand by 32% and increasing fresh weights of root and fresh weight of aerial biomass of plants over the untreated pathogen control by 6.95 g and 7.96 g, respectively. Strain SR19 is a potential biological control agent that may contribute to the protection of tomato plants against fusariose wilt.
ABSTRACT
Endophytic bacteria have been isolated from the roots of Urtica dioica. A total of 54 endophytic bacteria were isolated from the underground parts using suitable surface sterilisation protocol. Three isolates R45a; R45b; R21a were tested for antagonism effect against Fusarium oxysporum, Colletotrichum gloeosporioides, Rhizoctonia solani, Phytophthora parasitica in dual culture method. Significant inhibitory effects on mecylial radial growth have been revealed with a percentage superior or equal to 75%. These strains were Gram-positive rods. Cultures on nutrient agar showed irregular, entirely cream coloured colonies that are strictly aerobic and capable of forming endospore. They belong probably to the genus of Bacillus spp.