Genetic and Morpho-Agronomic Evaluation of New Tomato Breeding Lines Resistant to Bacterial Speck (Pseudomonas Syringae pv. Tomato)

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.