The Vh2 and Vh4 scab resistance genes in two differential hosts derived from Russian apple R12740-7A map to the same linkage group of apple (original) (raw)

Abstract

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 as _Vr_-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 name Vr with a scab resistance gene conditioning distinctive stellate necrotic reactions, which we refer to as _Vr_-A in order to distinguish it from _Vr_-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 named Vh2 and Vh4, 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 named _Vr_-A and Vx, respectively, in an F1 family of Russian apple. We showed that race 2 of V. inaequalis isolated 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-nonspecific _Vr_-DW gene, but in fact carry _Vr_-A. We conclude that the Vh2 gene in host 2 and _Vr_-A are the same, and that the Vh4 gene in host 4 and Vx are 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-nonspecific _Vr_-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 to Vh2.

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Author notes

  1. R.L. Rusholme
    Present address: School of Biological Sciences, University of East Anglia, NR4 7TJ, Norwich, UK

Authors and Affiliations

  1. The Horticulture and Food Research Institute of New Zealand Ltd, Hawkes Bay Research Centre, Private Bag 1401, Havelock North, New Zealand
    V.G.M. Bus
  2. The Horticulture and Food Research Institute of New Zealand Ltd, Mt Albert Research Centre, Private Bag 92169, Auckland, New Zealand
    E.H.A. Rikkerink
  3. Plant Research International, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
    W.E. van de Weg, L.P. Kodde & E.J. Meulenbroek
  4. The Horticulture and Food Research Institute of New Zealand Ltd, Palmerston North Research Centre, Private Bag 11030, Palmerston North, New Zealand
    R.L. Rusholme, S.E. Gardiner & H.C.M. Bassett
  5. Institut National de la Recherche Agronomique, Centre de Recherches d’ Angers, BP 57, 49071, Beaucouzé, France
    L. Parisi & F.N.D. Laurens
  6. The University of Auckland, School of Biological Sciences, Private Bag 92019, Auckland, New Zealand
    K.M. Plummer

Authors

  1. V.G.M. Bus
  2. E.H.A. Rikkerink
  3. W.E. van de Weg
  4. R.L. Rusholme
  5. S.E. Gardiner
  6. H.C.M. Bassett
  7. L.P. Kodde
  8. L. Parisi
  9. F.N.D. Laurens
  10. E.J. Meulenbroek
  11. K.M. Plummer

Corresponding author

Correspondence toV.G.M. Bus.

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Bus, V., Rikkerink, E., van de Weg, W. et al. The Vh2 and Vh4 scab resistance genes in two differential hosts derived from Russian apple R12740-7A map to the same linkage group of apple.Mol Breeding 15, 103–116 (2005). https://doi.org/10.1007/s11032-004-3609-5

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