VIEW ARTICLE

Physiology and Biochemistry

Differential Phytotoxicity of Peptides from Culture Fluids of Verticillium dahliae Races 1 and 2 and Their Relationship to Pathogenicity of the Fungi on Tomato. A. Nachmias, Department of Plant Pathology, University of California, Riverside 92521, Permanent address: Division of Plant Pathology, Agricultural Research Organization, Gilat Experiment Station, Negev, Israel; V. Buchner(2), L. Tsror(3), Y. Burstein(4), and N. Keen(5). (2)(4)Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel; (3)Division of Plant Pathology, Agricultural Research Organization, Gilat Experiment Station, Negev, Israel; (5)Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 77:506-510. Accepted for publication 29 May 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-506.

Confirming other work, we found that race 2 isolates of Verticillium dahliae caused severe symptoms on tomato plants carrying the Ve gene for Verticillium resistance, whereas race 1 isolates caused little or no damage. However, both fungi colonized Ve tomato stems and attained similar populations. Phytotoxic peptides were isolated from the culture fluids of V. dahliae races 1 and 2 and were found to differ in amino acid composition and toxicity to tomato leaves, root tips, and suspension cells. The race 1 peptide produced more severe symptoms in plants lacking the Ve gene than those that contained the Ve gene. On the other hand, the peptide from race 2 isolates produced indistinguishable, severe symptoms on both tomato genotypes. The results therefore suggest that the Ve gene may function by conferring tolerance to the phytotoxic effects of the race 1 peptide. The pathogenicity of race 2 isolates on Ve tomato plants may be due to their production of an altered peptide toxin, which causes severe effects on plants carrying the Ve gene as well as those lacking this gene.