ISHS Acta Horticulturae 595: International Symposium on Apple Breeding for Scab Resistance
ALTERNATIVE STRATEGIES TO FIGHT APPLE SCAB |
| Authors: | M. Mota, H. Pühringer, I. Zinöcker, C. Kaydamov, H. Katinger, M. Laimer da Câmara Machado |
| Keywords: | Venturia inaequalis, Malus domestica, PGIP, chitinase, resistance |
| Abstract:
In apple scab disease, the mycelium of the pathogen Venturia inaequalis grows between the cuticle and the epidermis. There it ramifies as a subcuticular stroma interacting with the underlying epidermal cells and deriving its nutrition from them without formation of intracellular haustoria. Therefore, genes encoding proteins which are expressed extracellularly and participate in the degradation of fungal cell wall, as well as genes involved in resistance mechanisms found in wild genotypes, represent good candidates for resistance breeding using transformation technology. In this respect the use of pathogen-inducible promoters, which are activated during the early stages of the infection process, would be a further benefit in the regulation of introduced ‘resistance‘ genes. Here we report the cloning of two different apple promoters which regulate gene expression of the polygalacturonase inhibiting protein (PGIP), as well as the isolation of two genes encoding chitinases from apple with features strongly pointing to extracellular expression. The characteristics of the pgip-promoters are currently analysed in Nicotiana tabacum transformed with the ß-glucuronidase marker gene (GUS). The different chitinase genes were isolated from a genomic library of Malus domestica and sequenced. The amino acid sequences show about 60-80% identity with acidic chitinases identified in other species. Currently, an RNA display is established in order to identify genes participating in the interaction of the resistant cv. Florina x Venturia inaequalis. | |
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