A SURVEY OF PHYTOALEXIN INDUCTION IN LEAVES OF THE ROSACEAE BY COPPERIONS

The leaves of 130 species of Rosaceae were surveyed for phytoalexin in duction. Both biotic and abiotic induction was examined and antifungal compounds were detected in 47 species. However. these compounds appea red to be constitutive metabolites, released from bound phenolic mater ials already present in the leaf. In Pyrus, hydroquinone was produced from the hydrolysis of arbutin present in the vacuole before inoculati on. In most other species, the fungitoxic agents were mainly catechin- like derivatives, apparently released from the tannins present within the leaf. By contrast, the synthesis in the leaf of the characteristic biphenyl or benzofuran phytoalexins which are produced in sapwood, wa s confined to a very few species. The biphenyl aucuparin was identifie d as a phytoalexin from the leaves of Sorbus aucuparia.