DURABILITY OF RESISTANCE IN LILY TO BASAL ROT - EVALUATION OF VIRULENCE AND AGGRESSIVENESS AMONG ISOLATES OF FUSARIUM-OXYSPORUM F SP LILII

Prospects of durability of resistance in lily to basal rot have been e valuated by testing the virulence and aggressiveness of 31 isolates of Fusarium oxysporum f. sp. lilii towards a number of different resista nce sources in Lilium spp. Isolates differed strongly in aggressivenes s as did species and cultivars of Lilium spp. in resistance. Significa nt interactions were observed between isolates of the pathogen and gen e types of Lilium spp., but the magnitude was very small compared to t he main effects. The interactions were mainly due to a small group of isolates with low aggressiveness. It is argued that the interactions m ight be based on minor genes. No major break down of the resistance wa s found. For practical purposes it will be sufficient to use highly ag gressive isolates in screening tests.