Abstract

A breeding program was initiated at the Research Institute of Vegetable Crops, Skierniewice, Poland to select new
tomato lines resistant to bacterial speck (Psedomonas syringae pv. tomato (PST) and suitable for field growing. Two
tomato cultivars with good agronomic characteristics Luban and Rumba were crossed with resistant to PST ‘Ontario
7710’. Then backcross and pedigree breeding procedures were employed to obtain BC5, BC4S1, BC3S2, BC2S3, BC1S4
populations. Screening test among those hybrid populations was performed in a greenhouse and exhibited a large
amount of variation in response to PST infection. All plants within BC1S4 progeny of the ‘Luban’ x ‘Ontario 7710’
cross and two BC1S4, BC3S2 progenies of the ‘Rumba’ x ‘Ontario 7710’ cross had no symptoms of bacterial speck and
could be assigned to the homozygous category. The remaining progenies were segregating for resistance and
susceptibility and gave distribution of plants over all severity classes. That confirms heterozygosity for resistant gene
Pto of their latter resistant single plant selections before backcrossing or/and selfing. The BC5 populations had
significantly higher disease severity rates (DSI = 2.4) than all other selfed populations (DSI = 1.2 – 1.6). After selection
resistant genotypes of the populations were transplanted to the field for morphological traits evaluation. A noticeable
progress in breeding regarding most of the plant and fruit characteristics of the recurrent parents was approached in all
populations of the ‘Luban’ x ‘Ontario 7710’ cross. Although all progenies of the ‘Rumba’ x ‘Ontario 7710’ differed
from their recurrent parent as to one feature at least, however the differences showed improved shifting toward the
characteristics of susceptible parent.

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