STIMULATION OF GERMINATION OF TELIOSPORES OF PUCCINIA-PUNCTIFORMIS BY NONYL, DECYL, AND DODECYL ISOTHIOCYANATES AND RELATED VOLATILE COMPOUNDS

Teliospores of Puccinia punctiformis (Strauss) Roehl. are dormant, overwintering propagules of Canada thistle rust. This rust fungus is a prospective biocontrol agent for Canada thistle (Cirsium arvense L.), a noxious weed. Nonyl, decyl, and dodecyl isothiocyanates stimulated germination of these teliospores at dosages of 5-25, 5-100, and 5-1000 μL/L, respectively. In preliminary tests, maximum percentage germination was 55% for nonyl-NCS, 70% for decyl-NCS, and 85% for dodecyl-NCS at 21 days, as compared to 0% germination in the controls. Dodecyl-NCS was most effective and active over the greatest dosage range, 5-1000 μL/L. The nonyl, decyl, and dodecyl isothiocyanates are the first compounds of known structure to stimulate germination of teliospores of P. punctiformis. Although volatiles from onion and garlic stimulated low levels of germination, various allyl sulfide and isothiocyanate derivatives reported to occur in Allium spp. were not stimulatory at dosage levels of 10-1000 μL/L. © 1990, American Chemical Society. All rights reserved.