DETERMINATION OF THE PHYSIOLOGICAL RACES OF FUSARIUM OXYSPORUM F. SP. DIANTHI ON CARNATION IN COLOMBIA
This work was conducted to determine the morphological, cultural, reproductive and pathological variability of 121 isolates collected from 61 farms located at the Bogotá Plateau. Nine foreign isolates of the races 1, 2, 4 and 8 were also used as controls. The pathogenicity tests were done by inoculation of rooted cuttings in six differential varieties.
All isolates had a radial rate of growth close to one centimeter per day. The colonies showed great variability in mycelial color, appearence and production of spores.
All 130 isolates of the fungus were pathogenic to one or more of the differential varieties used. There were some differences in incubation period, plant colonization and symptoms.
One hundred and twelve isolates were identified as Race 2 of the pathogen based on their reaction of resistance in Ibiza and Niki, and their reaction of susceptibility in Pink Calypso, Raggio di Sole and San Remo. Seven isolates could not be identified within the known races, due to its low level of pathogenicity and an inconsistent reaction in the differential varieties.
Four different reactions were found in Taiga, which is supposed to be resistant to all known races: Resistant (30%), Moderately Resistant (34%), Moderately Susceptible (21%) and Susceptible (15%). For these reactions we suggest the presence of four variants of race 2 of the pathogen. These reactions could explain the variable behavior of the some varieties in Colombia.