Pitblado, R. E., and E. A. Kerr A source of resistance to bacterial speck - Pseudomonas tomato.
Bacterial diseases, especially speck, have been increasing in importance in the northeast USA and Canada
in recent years. Present methods of control are expensive and only partially effective. Some cultivars e.g. Ottawa
78, Chico III and U.C. 134E appear to be very susceptible. Before 1978, no cultivar was reputed to have good
resistance although a few are listed in the Gene Resources of Canada as being tolerant.
In 1978 the senior author and J. K. Muehmer examined a large number of cultivars growing in the
experimental plots at Ridgetown College of Agricultural Technology and about 30 experimental cultivars growing in
a commercial field. One cultivar, Ont 7710, was immune under field conditions and two other cultivars from the
same parentage, Ont 7611 and Ont 782, were very highly resistant. Laboratory tests have confirmed the resistance
of Ont 7710 to the strain of P. tomato occurring in Ontario.
Ont 7710 has a complex ancestry: Viceroy/ 3/Pocomoke/Ace/3/ Camdown/4/Farthest North/Glamour/4/Early
Baltimore/5/Pritchard/3/Pocomoke/4/Florida 407//Glamour/5/Early Baltimore/6/Pritchard/4/Pokomoke/3/Roma
VF/5/H1350/6/High Crimson/4/High Crimson/5/Blitz. Most of the ancestral cultivars were tested in the laboratory.
Farthest North was the only one that proved resistant. Tests are now under way to determine the inheritance of this
resistance. We expect it will be fairly simple since it was fortuitously carried through four outcrosses to susceptible
cultivars. The presence of intermediate degrees of resistance in some cultivars and breeding lines indicates that
modifiers, or more than one major gene, are involved.
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