Biotic and abiotic elicitation of phytoalexins in leaves of groundnut (Arachis hypogaea L.)

Abstract

Four weeks after inoculation with Cercospora arachidicola (Mycosphaerella arachidis), Phaeoisariopsis personata (M. berkeleyi) and Puccinia arachidis, groundnut leaves (cultivar TMV2) accumulated 1830, 664 and 162 nmol phytoalexins/g fresh weight, respectively. Leaves infested with Frankliniella sp. for the same period contained 1.25 nmol phytoalexins/g fresh weight. Spraying abraded leaves with salicylic acid (0.02M) resulted in the accumulation of 1270 nmol phytoalexins/g fresh weight. 120 hours after treatment and irradiation of abaxial leaf surfaces with UV light (254 nm) for 48 hours and incubation in the dark for a further 96 hours caused the accumulation of 393 nmol phytoalexins/g fresh weight. Compounds with UV spectra corresponding to isoflavanones were almost exclusively synthesized in response to abiotic elicitors but in leaves infected with fungal pathogens formononetin, daidzein and medicarpin were present as minor components