D. Ganeva1*, K. Vasileva 1, N. Bogatzevska 2

1 Agricultural academy, Maritsa Vegetable Crops Research Institute, 32 Brezovsko shose, 4003 Plovdiv, Bulgaria
2 Agricultural academy, Institute of Soil Science, Agrotechnology and Plant Protection, Nikola Pushkarov, 1331 Sofia, Bulgaria

(Manuscript received 19 March 2026; accepted for publication 28 May 2026)
*e-mail: dganeva@abv.bg

Abstract. Bacterial speck (Pseudomonas syringae pv. tomato) and bacterial spot (Xanthomonas vesicatoria) are economically important diseases of tomato (Solanum lycopersicum) in Bulgaria. Breeding for resistance to bacterial pathogens is difficult because epiphytic and endophytic pathogenic populations are heterogeneous by species and races. Three-genome hybrid TGH (Solanum lycopersicum, Solanum chilense LA460 and Solanum peruvianum PI 127829) is the main donor of introgressed genes, which combine resistance alleles in lines L24, L44, L164, L166. Lines 346, 358, 404 have varying degrees of internal genetic cohesion and interline divergence. L346 and L358 are characterized by analogous resistance genes, whereas L404 exhibits a dominant hypersensitive response (HR). Following prolonged selection and repeated cross‑inoculation with pathogen races, a new immune line L404‑R has bred. Тhe introgression stabilizes the complex resistance to P. syringae pv. tomato (R0, R1) and X. vesicatoria (T1, T2, T3). The lines obtained represent a valuable selection resource for the development of cultivars and hybrids with durable and broad‑spectrum resistance.