VARIATION IN FUSARIUM-INDUCED ETHYLENE PRODUCTION AMONG TULIP CULTIVARS

Abstract

Ethylene evolution is a well-known consequence of Fusarium infection of tulip (Tulipa gesneriana) bulbs, yet little is known about the bulb-pathogen interactions involved in the induction or the time course of ethylene production in the infected bulb. Bulbs of 36 tulip cultivars were wounded, inoculated with a liquid Fusarium suspension (isolated from infected bulbs, and grown on agar plates) and held at 21°C. Control bulbs were wounded, but not inoculated. Ethylene production was monitored by headspace accumulation and gas chromatography. The results indicated that ethylene could increase rapidly after a lag phase of at least 8 days after inoculation, but there was a great variability in ethylene production among cultivars. Of the cultivars tested, the highest ethylene producer was ‘Furand’, which evolved more than 340 µl/kg fwt wt/h (ca. 250 µl/bulb/day) on the 12 th day after infection. By 19 days, inoculated ‘Furand’ and ‘Nashville’ produced ethylene at ca. 800 µl/bulb/day. Approximately 40% of the cultivars produced ethylene at rates greater than 150 µl/bulb/day, and only 11% of them produced less than 5 µl/bulb/day. These results suggest high-ethylene producing tulips should be stored separately from other cultivars, or that increased ventilation should be maintained during storage or transportation. Knowledge of cultivar variation might also be useful in breeding programs.