Biochemical responses during the pathogenesis of Sclerotium rolfsii on cowpea

Abstract

The hypersensitive reaction (HR), one of the most efficient and visible parts of the defense mechanisms in nature against invading pathogens, is associated with a coordinated and integrated set of metabolic alterations which are instrumental in impeding further pathogen ingress or alleviating stress. It includes a variety of novel proteins and secondary metabolites. This study aimed to examine the induction of different stress related enzymes like phenyl alanineammonia lyase (PAL), chitinase, β-1,3 glucanase, oxidative enzymes like peroxidases (POD), poly phenol oxidases (PPO) and phenolics after inoculation of Sclerotium rolfsii in collar region of 30 days old cowpea plant. Scanning electron microscopy strengthened the presence of mycelial network in xylem vessel of infected collar region of cowpea at three days after inoculation. Cowpea plants inoculated with S. rolfsii isolate showed significantly increased POD, PPO, PAL, chitinase and β-1, 3-glucanase activities at different days after inoculation. In the present study, there was a greater accumulation of total phenol in cowpea plants observed up to five days after inoculation. The highest activity of POD, SOD was found in three days after inoculation and PPO activity was greater in five days after inoculation and thereafter, the activities of such enzymes steadily decreased. It was due to susceptible interaction of S. rolfsii ingression in cowpea. The correlation study between disease progression and changes in activity of different defense related
enzymes showed that POD and chitinase were significantly associated with susceptible host pathogenic interaction in cowpea against S. rolfsii.

Keywords: Cowpea, Sclerotium rolfsii, defense-related enzymes, phenolics, pathogenesis related proteins, scanning electron microscopy

African Journal of BiotechnologyVol. 12(25), pp. 3968-3977