Partial resistance to black spot disease in diploid and tetraploid roses: general combining ability and implications for breeding and selection |
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Authors: | Vance M Whitaker Stan C Hokanson |
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Institution: | (1) Department of Horticultural Science, University of Minnesota, 1970 Folwell Ave., St. Paul, MN 55108, USA |
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Abstract: | Black spot disease, incited by the fungus Diplocarpon rosae Wolf, is the most important disease of roses (Rosa hybrida L.) in the outdoor landscape. Though partial resistance exists in cultivated germplasm, the genetic basis of this trait has
not yet been elucidated. Six diploid and six tetraploid rose cultivars were crossed in two factorial combining ability arrays.
Whole plant and detached leaf inoculation methods were used to assess partial resistance under two different disease pressures
using a characterized single-spore isolate. Parents from both arrays had significant general combining ability effects across
multiple inoculation methods and environments. Specific combining ability was not significant for either array. Parent per
se performance was highly correlated with progeny performance on a family mean basis. High positive correlations among whole
plant and detached leaf inoculation methods indicate that detached leaf assays can substitute for whole plant assays. Based
on these results, a breeding strategy including parental selection and early, among-family selection is proposed. To our knowledge,
this is the first investigation of combining ability for disease resistance in rose. |
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Keywords: | Black spot Combining ability Partial resistance Rosa |
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