EXPRESSION OF A CHITINASE TRANSGENE IN ROSE (ROSA-HYBRIDA L) REDUCES DEVELOPMENT OF BLACKSPOT DISEASE (DIPLOCARPON ROSAE WOLF)

Blackspot, caused by the Ascomycete fungus Diplocarpon rosae, is the m ost widespread and pernicious disease of cultivated roses. While some species of rose possess resistance to D. rosae, none of the modern-day rose cultivars are fully resistant to the pathogen. In the current st udy, Biolistic gene delivery was used to introduce a rice gene, encodi ng a basic (Class I), chitinase into embryogenic callus of the blacksp ot-susceptible rose (Rosa hybrida L.) cv. Glad Tidings. The plasmid us ed for transformation carried the neomycin phosphotransferase (nptII) gene facilitating the selection and regeneration of transgenic plants on medium containing 250 mg/l kanamycin. Southern analysis confirmed i ntegration of 2-6 copies of the chitinase gene into the rose genome; g ene expression was confirmed by enzyme assay. Bioassays demonstrated t hat expression of the chitinase transgene reduced the severity of blac kspot development by 13-43%. This degree of resistance to the pathogen correlated with the level of chitinase expression in the transgenic r ose plants. The introduction of disease defence genes into rose provid es a method of producing blackspot-resistant rose cultivars sought by breeders and growers.