Production of prunus necrotic ringspot virus-free roses by heat treatment and tissue culture

Abstract By a combination of heat treatment and tissue culture, virus was eliminated from 10 cut-flower cultivars and 1 rootstock cultivar. The roses, grown in hydroponics, were placed in an environmentally controlled cabinet and held at about 38°C. Heat stress occurred rapidly in all except the rootstock Rosa fortuniana Lindl. Survival time ranged from 8 to 20 days depending on the cultivar. Axillary buds removed from heattreated plants just before total collapse were established in tissue culture, but many degenerated and died after a few weeks. In one study of 1023 tissuecultured buds, only 45 survived to produce established plants in the glasshouse. In total, 79 tissuecultured plants were produced, and 62% of these were virus-free after 12 months of testing. These plants now form the nucleus of a Plant Improvement Program for roses in Victoria, Australia.