Effect of <i>Glomus mosseae</i> on concentrations of rosmarinic and caffeic acids and essential oil compounds in basil inoculated with <i>Fusarium oxysporum</i> f.sp. <i>basilici</i>

Abstract

This study investigated the potential of the arbuscular mycorrhizal (AM) fungus Glomus mosseae to protect basil ( Ocimum basilicum ) against Fusarium oxysporum f.sp. basilici ( Fob ). It was hypothesised that G. mosseae could confer a bioprotective effect against Fob as a result of increases in leaf rosmarinic (RA) and caffeic acids (CA) or essential oil concentrations. Glomus mosseae conferred a bioprotective effect against Fob by reducing plant mortality to 20% compared to 33% in non‐mycorrhizal (NM) plants. This bioprotective effect was not related to improved phosphorus (P) nutrition, as AM and NM plants treated with Fob had similar shoot P concentrations (6 and 8 mg g −1 dry weight (DW), respectively). Both AM and NM plants treated with Fob had similar leaf and root RA and CA concentrations. Furthermore, phenolic (40–70 mg CA g −1 DW) or essential oil concentrations (0·1–0·6 mg g −1 DW) were not increased in plants treated with the AM fungus and Fob . Therefore, the bioprotective effect conferred by G. mosseae was not a result of increases in the phytochemicals tested in this study. However, under the AM symbiosis, basil plants treated with Fob had lower methyleugenol concentrations in their leaves (0·1 mg g −1 DW) than NM plants treated with the pathogen (0·6 mg g −1 DW).