Articles
BREEDING FOR FIRE BLIGHT RESISTANCE AND STERILITY IN COTONEASTER
Article number
1056_35
Pages
221 – 224
Language
English
Abstract
Cotoneaster is a genus of over 400 species in the apple subfamily (Maloideae) commonly used as ornamental landscape plants.
Many species are extremely drought and urban tolerant, making them desirable for modern sustainable landscapes.
However, susceptibility to fire blight is common in the genus, which has reduced their use where there is significant disease pressure.
In addition to fire blight susceptibility, some species have escaped cultivation to form substantial populations in native areas.
We initiated a breeding program to develop disease resistant and sterile cotoneaster cultivars.
To identify potential sources of resistance, we artificially inoculated 52 taxa of Cotoneaster with Erwinia amylovora strain Ea153 at 109 and 106 CFU/ml during 2011 and 2012, respectively.
Percent shoot infection (lesion length/total shoot length) was used to assess disease severity.
Disease screenings were conducted over two years with 13 species repeated over years to validate results.
Susceptibility was highly variable among species.
Inoculation of several highly susceptible species resulted in whole plant mortality (C. rhytidophyllus, C. rugosus, C. wardii), while other taxa repeatedly showed no disease symptoms (C. arbusculus, C. sikagensis, C. splendens). We used results of our disease screening and ploidy level analysis to design crosses.
In 2011, among the crosses we performed was using C. splendens, a resistant tetraploid (2n = 4x = 68), as a pollen parent in crosses with the susceptible diploid (2n = 2x = 34) C. × suecicus Coral Beauty as the pistillate parent.
The resulting hybrids were screened using flow cytometry and confirmed to be triploids (2n = 3x = 52). These triploid hybrids have been propagated by stem cuttings and will be screened for fire blight susceptibility to determine heritability of resistance.
All hybrids will be evaluated for fertility, landscape performance, and aesthetics, as we have observed substantial phenotypic variability in leaf shape and habit among hybrids.
Many species are extremely drought and urban tolerant, making them desirable for modern sustainable landscapes.
However, susceptibility to fire blight is common in the genus, which has reduced their use where there is significant disease pressure.
In addition to fire blight susceptibility, some species have escaped cultivation to form substantial populations in native areas.
We initiated a breeding program to develop disease resistant and sterile cotoneaster cultivars.
To identify potential sources of resistance, we artificially inoculated 52 taxa of Cotoneaster with Erwinia amylovora strain Ea153 at 109 and 106 CFU/ml during 2011 and 2012, respectively.
Percent shoot infection (lesion length/total shoot length) was used to assess disease severity.
Disease screenings were conducted over two years with 13 species repeated over years to validate results.
Susceptibility was highly variable among species.
Inoculation of several highly susceptible species resulted in whole plant mortality (C. rhytidophyllus, C. rugosus, C. wardii), while other taxa repeatedly showed no disease symptoms (C. arbusculus, C. sikagensis, C. splendens). We used results of our disease screening and ploidy level analysis to design crosses.
In 2011, among the crosses we performed was using C. splendens, a resistant tetraploid (2n = 4x = 68), as a pollen parent in crosses with the susceptible diploid (2n = 2x = 34) C. × suecicus Coral Beauty as the pistillate parent.
The resulting hybrids were screened using flow cytometry and confirmed to be triploids (2n = 3x = 52). These triploid hybrids have been propagated by stem cuttings and will be screened for fire blight susceptibility to determine heritability of resistance.
All hybrids will be evaluated for fertility, landscape performance, and aesthetics, as we have observed substantial phenotypic variability in leaf shape and habit among hybrids.
Publication
Authors
R. Contreras, J. Rothleutner, V.O. Stockwell
Keywords
fire blight, sterility, invasive species
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