SENSITIVITY OF TULIP CULTIVARS TO EXOGENOUS ETHYLENE

Abstract

Since Fusarium fungus produces ethylene when infecting tulip bulbs, and tulip bulbs are sensitive to ethylene throughout the summer and fall storage periods, ethylene is of special concern for the tulip industry. It is less commonly appreciated that tulip cultivars can vary a great deal in the quantity of ethylene produced during Fusarium infection (Miller et al., 2005). In addition to variation in ethylene production from Fusarium infection, tulip cultivars also vary in sensitivity to ethylene. Over several years, we have exposed bulbs of 91 tulip cultivars to 10 µl L-1 ethylene in flowing air streams at 20°C, typically in October-November followed by a 4 week ethylene-free period at 17°C. Results indicate large cultivar differences in flower abortion when bulbs are forced the following spring. The picture is emerging that ca. 35-50% of tulip cultivars are substantially resistant to 10 µl L-1 ethylene when given to bulbs in the October-November time period, based on consistency of resistance (i.e., no flower abortion) within and between years of testing. Other cultivars are consistently susceptible to ethylene (about 51% of cultivars). Other cultivars have shown an inconsistent response across years (about 15% of cultivars). Within a year, ethylene sensitivity invariably increases with later ethylene exposure (e.g., early October vs. late November). It is unknown whether similar results would be seen with ethylene exposure earlier in the season (e.g., July-September). These results should be of interest for breeding ethylene resistant cultivars and managing risk during tulip handling.