Effect of African basil (<i>Ocimum gratissimum</i>) extracts against Water mould (<i>Pythium aphanidermatum</i>) in cowpea

Abstract

The experiment was designed to investigate the effects of Ocimum gratissimum extracts in the control of Pythium aphanidermatum in cowpea. This was conducted in Crop Science and Biotechnology laboratory, Imo State University, Owerri between May to August 2018 using completely randomized design (C.R.D). There were 8 treatments replicated 4 times. Powder and Liquid extracts of the leaves of Ocimum gratissimum were applied at different concentrations (0,5, 10, 15) g and (0, 5, 10, 15) mls respectively, inoculated on the media, Potato Dextrose Agar (PDA) in petri dishes to check the incidence and spread of the disease. Extracts of Ocimum gratissimum were effective against Pythium aphanidermatum in all the parameters tested. On inoculation of PDA media, different forms of Pythium aphanidermatum (ring or circular and dotted) in all treatments were observed, except the control. Quantitative analyses and Infrared spectroscopy of Ocimum gratissimum leaf extracts revealed the presence of active phytochemicals (alkaloids 3.6, tannins 15.4, flavonoids, oxalate 5.8, saponins 3.1) ug/g and infrared compounds (alkenes (3201.2), alcohol (3344.5), carboxylic acid (2995.5), aldehyde (2719.5), and isocyanate (2804.4) absorbed at different wave lengths in cm-1 were identified.
Different fungal growths were cleared using different levels of extracts, (15>10>5>0) mls than
powder extracts respectively. The ability of the extracts to exert fungicidal effects was due to the
presence of active phytochemicals and infrared compounds present in the extracts.