Induction of Systemic Acquired Resistance in Hevea Brasiliensis by an Endophytic Bacterium Antagonistic to Phytophthora Maedii

Abstract

Abnormal leaf fall (ALF) disease caused by Phytophthora meadii McRae is one of the limiting factors of growth and latex yield in Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg. Endophytic bacteria residing within the host plant offer very high application potential as biocontrol agents for ALF disease management. Screening of bacterial endophytes from leaf, petiole and root tissues of Hevea brasiliensis was done for the selection of a potent antagonistic isolate against P. meadii. The most efficient antagonistic isolate was identified as Alcaligenes sp. The biochemical estimation of antagonist treated plants showed induction of peroxidase activity in leaves. Quantitative PCR analysis confirmed higher activity of lignin biosynthesis promoting class III peroxidase transcripts in antagonist treated plants of H. brasiliensis. Homology model of the peroxidase class III protein was built from the deduced amino acid sequence and was found to carry 36% helical and 5% beta sheets. Computer aided docking studies of the substrates (p-coumaryl, coniferyl and sinapyl alcohol) with the target proteins showed that the protein-substrate complexes were stabilized by various interactions and proposed that precursors of lignin biosynthesis were preferred by induced peroxidase in Hevea brasiliensis for lignifications. The present study revealed the potential of an antagonistic endophyte Alcaligenes sp. EIL-2 for inducing class III peroxidase involved in defence mechanism in Hevea brasiliensis.