Elimination of rose viruses using microshoot tip tissue culture

Abstract

Virus elimination therapy for roses is very challenging. Foundation Plant Services at the University of California, Davis provides virus-tested rose propagation material to the rose nursery industry in the United States. Before 1999, heat treatment of potted plants was used to eliminate viruses. Success was varied and often the plant died during the treatment or was still virus-infected at the end of treatment period. In 2007 we reported on successful elimination of Apple mosaic virus (ApMV) and Prunus necrotic ringspot virus (PNRSV) using microshoot tip culture for six cultivars. However, survival was low and was cultivar dependent. In the period 2013 to 2016, 35 rose cultivars were subjected to microshoot tip tissue culture therapy. Microshoot tips measuring <0.5 to 0.7 mm, consisting of the meristem dome plus several pairs of leaf primordia, were excised from actively growing vegetative shoots and cultured in aseptic conditions. Different media, growth factors and light intensity were trialed. To date the most promising medium is: Murashige and Skoog (MS) salts and vitamins with 3% sucrose, 2.5 µmol 6-benzyladeninepurine (BA) and 0.4 µmol indole-3-acetic acid (IAA). Rooting was ex vitro by transplanting shoots that were approximately 5 cm long into a sealed container of saturated perlite to keep humidity high. One or more plants survived from 20 cultivars of the 35 that were treated (56%). Overall percent survival averaged 3% and ranged from 0 to 22%, depending on cultivar. Preliminary testing by ELISA shows that ApMV was eliminated; plants were still infected with PNRSV. Further testing using qPCR and other methods and trials are ongoing.