Relationship of the production of the toxin, cerato-ulmin, to synnemata formation, pathogenicity, mycelial habit, and growth of Ceratocystis ulmi isolates

Abstract

Forty-seven isolates of Ceratocystis ulmi collected from Canada, the United States, the United Kingdom, France, the Netherlands, and Iran were classified with respect to their ability to produce cerato-ulmin (CU) and synnemata, their radial growth, mycelial habit, and pathogenicity.Twenty-nine isolates clearly produced CU in a measurable quantity while 18 isolates produced it only in trace quantities. In general, the former produced fluffy mycelium and were active in synnemata formation. They were aggressive in pathogenicity with one exception. The latter group of isolates generally produced waxy, yeastlike mycelium and formed very few synnemata. They were all nonaggressive in pathogenicity. Radial growth was generally higher among the isolates that produced CU in larger quantities than among those producing CU in trace quantities. The relationship between CU production and pathogenicity affords a method for estimating isolate pathogenicity without the need for host inoculation.