Ethylene Exposure Exacerbates Botrytis Damage in Cut Roses1

Separate experiments showed that current cut rose (Rosa × hybrida) cultivars vary considerably in Botrytis (Botrytis cinerea) susceptibility and ethylene (ET) sensitivity. There was no pattern when considering these two traits together for the 26 cultivars used, and neither trait appeared predictive of the other. Four cultivars were identified that included one each that is Botrytis susceptible/ET sensitive, Botrytis non-susceptible/ET sensitive, Botrytis susceptible/ET insensitive, and Botrytis non-susceptible/ET insensitive. Exposing these cultivars to ET often resulted in reduced vase life and more pronounced negative Botrytis responses (flower Botrytis damage, leaf Botrytis incidence, and frequency of termination due to Botrytis). This was true for ET sensitive and insensitive cultivars, Botrytis susceptible and non-susceptible cultivars, Botrytis inoculated and non-inoculated stems, and stems exposed to ET either before or after Botrytis inoculation and incubation. Thus, even if ET is not thought to have a major influence on a given cut rose cultivar in terms of classic negative ET responses (leaf drop, petal wilt, altered opening rate), ET exposure could have a significant negative impact on that cultivar by exacerbating Botrytis damage. Shipping temperatures and methods can have a strong influence on Botrytis damage, with pre-cooling of shipping boxes before cold storage/transport being beneficial. Index words: Botrytis blight, Botrytis cinerea, cut flowers, floriculture, gray mold, Rosa L. hybrids. Species used in this study: Rose (Rosa × hybrida) focal cultivars ‘Cuenca', ‘Daphnee', ‘Freedom', ‘Vendela'; Botrytis (Botrytis cinerea Pers. ex. Fr.). Chemicals used in this study: 1-methylcyclopropene (EthylBloc); ethylene; silver thiosulfate.