QUANTITATIVE RESISTANCE OF CIRSIUM-ARVENSE TO ROOT BUD INFECTION BY PUCCINIA-PUNCTIFORMIS

A method is presented to test clones of Cirsium arvense for resistance to root bud infection by the rust fungus Puccinia punctiformis. Root buds were stained and cleared to detect mycelium of the rust. The frac tion of root buds infected was determined and used as a measure of res istance. Clones of C. arvense, collected from three sites, were tested for resistance to infection. Variation in resistance was determined b etween and within sites. The results are discussed with a view to usin g P. punctiformis to control C. arvense.