Isolation and evaluation of endophytic bacteria from rubber leaves (hevea brasiliensis) against circular leaf spot disease

Abstract

This study was conducted at the Rubber Research Institute, Dartonfield, Agalawatta, Sri Lanka to identify alternative biological control agents to manage the Circular Leaf Spot Disease in rubber cultivation. The newly reported Circular Leaf Spot Disease caused by the Colletotrichum spp and Pestalotioides group which is distributed in Sri Lanka and also other rubber growing countries in the world. In Sri Lanka, the incidence of the disease is increasingly destructive in rubber plantations. In this study, we isolated endophytic bacteria to assess their antagonistic activity against pathogens causing Circular Leaf Spot Disease (Gunarathne & Fernando, 2017). The endophytic bacteria were isolated from Rubber leaves using 3 clones (RRIC 100,121 and RRISL 203) at bud wood nursery. The isolated endophytic bacteria were analyzed using cultural and microscopic characters. Results revealed that 16 endophytic bacteria were isolated and six strains (Ctr EB1, P44, EB3, Cfr EB4, Cfr EB1, Cfr EB4 and P20 EB5) were identified as the most potent antagonistic endophytic bacteria based on their inhibition percentage. This study highlights the high potential of the isolated highest inhibition percentage endophytic bacteria to combat the circular leaf spot pathogens in Hevea brasiliensis.