Antagonistic Activities of Selected Bacterial Isolates Against Soilborne Disease Pathogens of Turfgrass

Abstract

Disease samples exhibiting symptoms of brown patch, yellow patch and Pythium blight were taken from several golf courses in Malaysia Isolation and identification of the pathogens indicated that Rhizoctonia solani Kuhn, Rhizoctonia cerealis Van der Hoeven and Pythium aphanidermatum (Edson) Fitzpatrick were the causal agents respectively. Identification of the pathogens was based on their morphological characteristics. Isolation of bacteria from thatch resulted in the isolation of ten bacterial isolates of which five were found to be antagonistic against the pathogens. The bacterial isolates were identified as Burkholderia cepacia (syn. Pseudomona. cepacia), Serratia marcescens, Chromobacterium violaceum, Pseudomonas aeruginosa and Bacillus megaterium. B.cepacia, P. aeruginosa and B. megaterium were found to 􀂎 antagonistic to R. solani with radial growth of 2.1 em, 2.1 em and 1.8 em respectively; to R cerealis with radial growth of 2.1 em, 2.1 em and 1.7 em respectively; and to P. aphanidermqtum with radial SfOwth of 2.1 em, 2.S cm and 1.5 em respectively; while S. marcesceflS and C. vio/aceum w􀋸e only antagonistic to P. aphanidermatum with radial growth of 2.6 em and 2.0 􀂴m respectively. All th􀂵 above m:easuretn􀂶nts were taken 3 days after inoculation. Microscopic observation of anta􀂷onistic mechanism displayed by the bacteria against the pathogens revealed that B. cepaciq, B. megatetiu"" C. violaceum and s. marcesce􀀵 degraded the cell wall, while P. aeruginosa suppressed or retarded the fungal growth. Cell wall degradation was due to the action of enzymes such as 13-1.3 glucanase and chitinase, whereas growth suppression was due to the action of siderophores. R solqni and R. cereq/is were inhibited by the bacteria via tbe action of a-I.3 glucanase, siderophores and antibiotics, whileP. ap/ti:midermatum was inhibited by the bacteria via the action of the above chemicals including chitinase.