ISHS Acta Horticulturae 663: XI Eucarpia Symposium on Fruit Breeding and Genetics
DEVELOPMENT OF MOLECULAR MARKERS FOR VR1, A SCAB RESISTANCE FACTOR FROM R12740-7A APPLE |
| Authors: | A. Boudichevskaia, H. Flachowsky, C. Fischer, V. Hanke, F. Dunemann |
| Keywords: | Venturia inaequalis, Malus, disease resistance, gene mapping, DNA markers, |
| Abstract:
The major scab resistance source from the apple R12740-7A (Russian seedling) is considered to be a valuable alternative to the Vf scab resistance. This investi-gation focuses on the identification and mapping of molecular markers linked to the genetic factors involved in the Russian seedling scab resistance. RAPD marker tech-niques together with BSA (Bulked Segregant Analysis) was performed using three apple progenies segregating for resistance/susceptibility in a pseudo-testcross situa-tion. The resistant parent in the crosses was the cultivar ‘Regia’. Two polymorphic markers were identified on the basis of resistant and susceptible pools (OPAD13950 and OPQ71500). Based on the sequence data of the cloned OPAD13950 fragment, SCAR primers were developed. The codominant AD13-SCAR can be used to differentiate heterozygous resistant from homozygous resistant plants. A multiplexing PCR assay using the new SCAR AD13 together with the Vf-SCAR AL07 was developed for an efficient molecular screening of seedlings obtained from crosses between Vf donors and the cultivars derived from the Russian seedling. The location of the scab resistant factor at the top of the apple linkage group 2 was verified by SSR mapping. Because Vr was mapped by Hemmat et al. (2002) on the middle-bottom part of linkage group 2, we propose to name the newly mapped gene Vr1. The S22-SCAR marker recently published by Hemmat et al. (2002) for a second locus involved in Russian seedling resistance (Vx) was found to be linked with several SSR loci from linkage group 2 as well as with the RAPD marker OPAD13950 and the AD13-SCAR. This suggests that: (1) Vx might be Vr1, and (2) that Vx/Vr1 and Vr resistance genes are located – over a large distance – on the apple linkage group 2. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
