ISHS Acta Horticulturae 508: XIX International Symposium on Improvement of Ornamental Plants
EVALUATION OF THREE STRATEGIES TO OBTAIN VIRUSES RESISTANT PELARGONIUM TRANSFORMED PLANTS |
| Authors: | R. Berthomé, M. Tepfer, S. Hanteville, J.P. Renou, J. Albouy |
| Keywords: | Pelargonium, transgenic plants, virus resistance, coat protein, 2'-5' oligoadenylate synthetase, Pac1 |
| Abstract:
Geranium (Pelargonium) is one of the most important ornamental production in Europe. Commercially, geranium plants are mainly produced from cuttings. Since the number of infected plants has increased considerably in the last 5 years, vegetative propagation is the primary means of transmission of several viruses. The most serious problems are presented by members of the Tombusviridae, such as pelargonium flower break carmovirus (PFBV), pelargonium line pattern carmovirus (PLPV) and pelargonium ringspot carmovirus (PRSV). For these reasons, in the absence of known sources of natural virus resistance, we are evaluating several strategies to create virus resistance by genetic transformation. Since PFBV is the most important geranium virus, we have cloned and sequenced its coat protein (CP) gene (Berthomé et al., 1998). A chimeric gene composed of the CaMV 35S promoter with a doubled enhancer, the PFBV CP cDNA, and the CaMV terminator (35S2-cpPFBV) was constructed in order to confer resistance specific to this virus. Since geraniums are infected by many viruses, we are also testing less well known strategies that have been shown to confer more broad range resistance (Robaglia and Tepfer; 1996). Thus, we have constructed a chimeric gene with a cDNAs encoding the rat 2'-5' oligoadenylate synthetase (2–5A; Truve et al., 1993), which plays a key role in the degradation of the viral single-stranded RNAs in mammalian cells (35S2–2–5A). We have also contructed a gene encoding Pac1 (Watanabe et al., 1995; Sano et al., 1997), which is a double-stranded RNA-specific ribonuclease from Schizosaccharomyces pombe (35S2-Pac1). Seedlings of Pelargonium X hortorum "pulsar saumon" (Sandoz seeds) were transformed according to Robichon et al. (1995). Forty-three transgenic RO plants with the 35S2-cpPFVB gene and seventeen with the 35S2–2–5A gene were identified using PCR. The lines were screened for transgene expression by northern blot and western blot analysis. In order to determine the degree of resistance conferred by those genes, ten three-weeks-old cuttings of each selected line will be tested for resistance to different geranium viruses. Immunoenzymatic methods (ELISA) will be used to detect viruses in inoculated and systemic leaves. Strategies will be compared for their effectiveness, and resistance tests will be repeated to confirm the stability of the resistance. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
