Biochemical and histochemical analyses revealing endophytic Alcaligenes faecalis mediated suppression of oxidative stress in Abelmoschus esculentus challenged with Sclerotium rolfsii.
Sclerotium rolfsii is a highly aggressive pathogen that causes huge economic losses, especially in temperate climates. Alcaligenes faecalis, particularly in endophytic form, has rarely been used to control this fungus. In this study, endophytic Alcaligenes sp. strain BHU 12, BHU 16 (isolated from Abelmoschus esculentus leaf) and BHU M7 (isolated from Andrographis paniculata leaf) were reported to trigger a wide range of host defenses in Okra plant against the collar-rot pathogen S. rolfsii. Endophytic colonization of the strains in ten days old plants was assessed through re-isolation of the rif-tagged strains on rifampicin augmented nutrient agar media. The ability of the endophytic strains to induce systemic defense responses in above-ground organs was assessed by collecting leaf tissues of the Okra plants grown under non-gnotobiotic conditions at different time intervals post seedling bacterization with the endophytic biocontrol agents. The pathogen challenged unprimed plants exhibited flaccidity of the stem and leaves at 48 h post infection (hpi) in contrast to the bioprimed and challenged plants. Biochemical and histochemical analyses explained the above phenomenon as activation of phyto-peroxidases leading to an increased metabolism of the reactive oxygen species (ROS), accompanied by activation of the phenylpropanoid network and a subsequent enhancement in plant phenolics. Interestingly, though the maximum increase in the defense pathways was observed in treatments with native endophytes of Okra plant, yet the enhancement in antioxidant pathway due to A. paniculata borne endophytes was also quite significant. Thus, this work clearly demonstrates how Okra plants respond to the "non-hostile" colonization of bacterial endophytes and how induced defense response can contribute to the biocontrol activity of the endophytic strains.
Department of Botany, Institute of Science, Banaras Hindu University, India.
Shatrupa
S
Ray
Department of Botany, Institute of Science, Banaras Hindu University, India; Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India.
Vivek
V
Singh
Department of Botany, Institute of Science, Banaras Hindu University, India.
Surendra
S
Singh
Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India.
Birinchi Kumar
BK
Sarma
Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India. Electronic address: hbs1@rediffmail.com.
Harikesh Bahadur
HB
Singh
D028483:Abelmoschus / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology*; D042481:Alcaligenes faecalis / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D001203:Ascomycota / Q000472:pathogenicity*; D001205:Ascorbic Acid / Q000378:metabolism; D016923:Cell Death; D060026:Endophytes / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006861:Hydrogen Peroxide / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D015227:Lipid Peroxidation; D018384:Oxidative Stress; D010935:Plant Diseases / Q000382:microbiology* / Q000517:prevention & control; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D000975:Antioxidants; D017382:Reactive Oxygen Species; D013481:Superoxides; D008031:Lignin; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid
Abelmoschus esculentus; Defense; Disease resistance; Endophytic bacteria; Phenylpropanoid pathway; Sclerotium rolfsii