ICE NUCLEATION ACTIVITY IDENTIFIED IN SOME PHYTOPATHOGENIC FUSARIUM SPECIES

In order to know which species of Fusarium are ice nucleating and to d etermine the factors affecting their pathogenicity, ice nucleation act ivity (INA) was examined in Fusarium oxysporum, F. sporotrichioides, a nd F. tricinctum. Positive controls [Ina(+)] used were F. acuminatum a nd F. avenaceum. The test for fungal INA was done with a simple and ra pid tube nucleation assay. Twelve out of the 42 F. oxysporum isolates, and 8 out of 14 F. tricinctum isolates were Ina(+). No INA was detect ed in F. sporotrichioides. In this test, the threshold freezing temper ature tended to increase with culture age, reaching a peak of -1 degre es C in a few samples, which is as high as the warmest INA reported fo r bacteria, and higher than the INA detected in pure cultures of free- living fungi, lichen fungi, lichen algae and cyanobacteria. This is th e first report of INA for F. oxysporum.