Phenols in spikelets and leaves of field-grown oats (Avena sativa) with different inherent resistance to crown rust (Puccinia coronata f. sp. avenae)

Abstract

BACKGROUND: Avenanthramides, health-beneficial phenols in oats, are produced in response to incompatible races of the crown rust fungus, Puccinia coronata, in seedlings of greenhouse-grown oats. This study aimed to elucidate whether avenanthramides and/or other phenolic compounds, together with the activities of phenylalanine ammonia lyase (PAL), phenoloxidase (PO) and the avenanthramide biosynthetic enzyme hydroxycinnamoyl-CoA: hydroxyanthranilate-N-hydroxycinnamoyl transferase (HHT), are associated with crown rust infection in mature field-grown oats. Nine oat (Avena sativa L.) genotypes with wide variation in crown rust resistance were exposed to naturally occurring fungal spores during the growth period. RESULTS: In the spikelets avenanthramidesas well as HHT activities were more abundant in the crown rust resistant genotypes, whereas p-coumaric and caffeic acids were more abundant in the susceptible ones. In the leaves avenanthramides were not associated with resistance. Instead two unknown compounds correlated negatively with the rust score. Phenols released by alkaline hydrolysis and PAL and PO activities were not related to rust infection, either in spikelets or in the leaves. CONCLUSION: Because grains of crown rust-resistant oat genotypes seemed to have higher endogenous levels of health-promoting avenanthramides, use of resistant oats may contribute to a food raw material with health-beneficial effects. © 2009 Society of Chemical Industry.