An Enzymic Basis for Pathogenic Specificity

Abstract

A SUBSTANCE present in oat roots and leaves which inhibits growth and respiration of several fungi has been described¹. It was suggested that the resistance of oats to Ophiobolus graminis, the cause of take-all of wheat, and its susceptibility to the very similar O. graminis var. avenae, was connected with this inhibitor, since var. avenae (O isolates) grew in sap expressed from oat roots whereas O. graminis itself (W isolates) did not. However, crudely purified inhibitor seemed equally toxic to both. This inhibitor has now been purified by H. K. Mitchell and J. V. Maizel and named ‘avenacin’ (personal communication). They find it to be identical with a fluorescent glucoside described as occurring in oat root meristems by Goodwin². They give the ED ₅₀ against Neurospora crassa growing in Fries medium as 0.4 µgm./ml. They find that on hydrolysis in 0.1 N hydrochloric acid, it loses its biological activity, and glucose and an unidentified pentose are released (Maizel, J. V., and Mitchell, H. K., unpublished work).