| Autor: |
Bus, V.G.M., Rikkerink, E.H.A., van de Weg, W.E., Rusholme, R.L., Gardiner, S.E., Bassett, H.C.M., Kodde, L.P., Parisi, L., Laurens, F.N.D., Meulenbroek, E.J., Plummer, K.M. |
| Předmět: |
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| Zdroj: |
Molecular Breeding; Jan2005, Vol. 15 Issue 1, p103-116, 14p |
| Abstrakt: |
Russian apple R12740-7A is the designation for an accession grown from seed collected in Russia, which was found to be highly resistant to apple scab. The resistance has historically been attributed to a naturally pyramided complex involving three major genes: one race-nonspecific gene,Vr, conditioning resistance to all known races, plus two race-specific genes. The race-nonspecific gene was identified as an independently segregating gene by Dayton and Williams (1968) and is referred to in this paper asVr-DW. The first researchers to study the scab resistance gene complex in Russian apple never described the phenotype conditioned by the race-nonspecific gene. Later, Aldwinckle et al. (1976) associated the nameVrwith a scab resistance gene conditioning distinctive stellate necrotic reactions, which we refer to asVr-A in order to distinguish it fromVr-DW. We show that the segregation ratios in progenies from the scab differential hosts 2 and 4 that are derived from Russian apple, crossed with susceptible cultivars were consistent with a single gene conditioning resistance in each host. The genes have been namedVh2andVh4, respectively. Resistant segregants from host 2 showed stellate necrotic reactions, while those from host 4 showed hypersensitive reactions. Both the phenotypes and the genetic maps for the genes in the respective hosts were very similar to those of the genes previously namedVr-A andVx, respectively, in an F1 family of Russian apple. We showed that race 2 ofV. inaequalisisolated from host 2 was able to infect resistant descendants of the non-differential accession PRI 442-23 as well as host 2. The descendants of PRI 442-23 were expected to carry the race-nonspecificVr-DW gene, but in fact carryVr-A. We conclude that theVh2gene in host 2 andVr-A are the same, and that theVh4gene in host 4 andVxare the same. However, a major finding of this study is that the latter gene mapped to linkage group 2 of apple instead of linkage group 10 as suggested from previous research. With the two race-specific genes from Russian apple defined now, we discuss the nature of the race-nonspecificVr-DW gene in this accession. We also report the identification of a new scab resistance gene,VT57, from either ‘Golden Delicious’ or ‘Red Dougherty’, which conditions chlorotic resistance reactions and is linked toVh2. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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