Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2006
Publication Date: 3/30/2006
Citation: Luby, J., Hokanson, K., Forsline, P.L., Aldwinckle, H., Gardiner, S., Bus, V. 2006. Evaluation of horticulturally elite malus sieversii germplasm for apple scab resistance genes using phenotypic and marker-based screenings. Meeting Abstract. 3rd International Rosaceae Genomics Conference. Pg. 75.
Interpretive Summary: Not Applicable
Technical Abstract: Apple scab (Venturia inaequalis) resistance was assessed for 39 horticulturally elite accessions of Malus sieversii collected in Kazakhstan. Based on inoculation with V. inaequalis (Race? Or composite?), eight of the 39 accessions were resistant. DNA was collected from each elite accession and screened for presence of markers that have been reported to be linked to specific known scab resistance genes based on previous research with other germplasm. None of the elite accessions were positive for markers linked with Vm (LG 17) or Vf (LG 1). Eleven accessions had positive reactions with a marker linked to Vb on LG 1. Numerous accessions, including both resistant and susceptible phenotypes, had positive reactions with markers linked to a group of several reported resistance genes on LG 2 including Vh2/Vr, Vh4/Vx, and Vh8, a recently described resistance gene that was discovered in other M. sieversii germplasm. Of the accessions that had resistant phenotypes when screened, those testing positive for several markers associated with Vh2/Vr and Vh8 included PIs 613987, 613991, 613998, and 613951. Resistant accessions testing positive for markers associated with Vx/Vh4 or Vr2 include PIs 613992, 613951, and 613957. Seven of the elite accessions were crossed with the susceptible cultivar Royal Gala and seedlings were screened with V. inaequalis races 1 and 2. The proportion of resistant progeny, combined over both races, ranged from nine to 67%. Four crosses gave significantly different proportions of resistant progeny in screens with race 1 compared with race 2. DNA was extracted from seedlings from 6 of these families and screened with up to eight markers linked to R genes on LG 2. Correlation of the markers with phenotype indicated some M. sieversii parents likely had known resistance genes but, in some cases, exhibited patterns suggesting they also contained novel resistance loci.