An improved method for selection of antagonistic bacteria against Phytophthora capsici Leonian infections in black pepper (Piper nigrum L.)

Abstract

An improved and rapid method for selection of bacteria primarily based on its inhibitoryeffect on pathogenesis of Phytophthora capsici on black pepper (Piper nigrum) was developed.Reductions in mycelial growth of P. capsici in dual plating assay and inhibition of lesion onexcised black pepper shoots in planta assay were calculated.  The inhibition ranged from 0.0%to 92.8% among the 19 bacterial isolates tested against P. capsici in the  in planta assay IIIwhere the bacterized shoots were challenge inoculated with P. capsici. The  in planta assay IIIcould select only two bacterial strains among the 19 isolates as effective against P. capsiciwhereas, four and six bacterial strains in the in planta assays I and II, respectively. The dualplate method, where only two-way interaction between the pathogen and antagonist wasstudied, could select four bacterial strains as effective ones. The  in planta selected bacterialstrains could protect the black pepper plants from foot rot infection when tested in thenursery. The  in planta assay based on this three-way interaction among black pepper (host)-P. capsici  (pathogen)-candidate bacterial strains (antagonist) was found to be an effectivemethod to select antagonistic bacteria against the foot rot pathogen.