Agriculture Reference
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Relative susceptibility of pear scion cultivars and of rootstocks for
pear to fire blight following artificial inoculation.
Incidence reflects frequency of infection (scale -). Severity is also on a scale
of (least severe) to (most severe). Indexreflects both these factors on a
scale of to . Class gives a broad band grouping from (most resistant)
to (most susceptible).
Table
.
Cultivar
Incidence
Severity
IndexClass
Pear cvs.
'Conference'
'Beurre Bosc'
'Blanquilla'
'Coscia'
'Jules Guyot'
'Beurr´eHardy'
'Abb ´e Fetel'
'Bartlett'
'Passe Crassane' a
'Packham's Triumph'
'Doyenne du Comice'
Pear rootstocks
INRA Pyriam (OH)
Farold Daytor
Quince BA
Quince C (EM)
Quince 'Adams'
Quince 'Sydo'
a Very susceptible on secondary blossom.
Adapted from Lespinasse and Aldwinkle (
), with permission.
flowers, for example, are very highly susceptible although shoot susceptibility
is only moderate.
Approaches to control involve minimizing tree susceptibility, reducing inocu-
lum levels and interfering with the infection process (Aldwinkle and Beer,
). There are, as yet, no curative treatments.
Breeding programmes for fire blight resistance, detailed earlier, show
promise. However, the economic superiority of high-density planting systems
using the susceptible 'M.
' rootstock, and the increasing market demand for
newer apple cultivars such as 'Fuji' and 'Gala', which are more susceptible
than the hitherto dominant 'Red Delicious', coupled with the shifting of the
bulk of apple production to warmer areas than hitherto, have all increased
rather than reduced fire blight problems. Reducing the succulence of growth
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