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This investigation was directed to sunflower improvement using hybrid forms resulted from wide hybridization. The aim was to create new B/A and R lines from interspecific and intergeneric hybrids resistant to diseases, parasite broomrape, herbicides, other stress factors and with high combining ability in highly productive oil-type sunflower hybrids with varied fatty acid contents. The confectionary hybrids should have a high kernel protein content and amino acid content.The investigation was carried out during the period 1983-2010. The programme included 16 cultivars and 18 B lines with their analogues. Interspecific, intraspecific, and intergeneric hybridization produced hybrid materials originating from 38 Helianthus species with different ploidy levels, 9 annuals and 29 perennials, and 28 species from other genera of family Compositae. New sunflower forms and lines created possessed resistance to downy mildew, Phomopsis, Phoma and Alternaria, tolerance to Sclerotinia and total resistance to the different races of parasitic broomrape. The new forms had distinctive plant architecture, different vegetation periods, and seeds of different sizes and coloration. New B/A and R lines, characterized with high combining ability, seed oil, and fatty acid content and varying protein amino acid contents were obtained. Fifteen sources of cytoplasmic male sterility (cms) were obtained from interspecific hybrids and 271 sources of fertility restoration (Rf) genes from interspecific and intergeneric hybrids. Five new oil type hybrids and one confectionery type were developed and registered.The results from this investigations showed that by wide hybridization new genetic material can be transferred to the cultivated sunflower. These results supplemented the contribution of interspecific and intergeneric hybridization for sunflower breeding.

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As a result of hybridization between the Bulgarian fertility restorer line R 2574 and mixed pollen from a polycross population of known genetic composition, and treatment of immature embryos with gamma radiation or ultrasound, a large number of new fertility restorer lines were developed. Lines R 114, R 115, and R 116, subjected to investigation in this study, are characterized with significant changes concerning most of the studied characters. The increased number of seeds per head in lines R 115 and R 116, the increased 1000 seed weight in line R 114, the 100% resistance to the parasite Orobanche in lines R 114 and R 116, and the very good combining ability in hybridization are the desired combination in the breeding program of sunflower. The hybrids Rada and 80, developed with the participation of lines R 114 and R 116, considerably exceeded the mean standard (the Bulgarian commercial hybrids Albena and Super Start) in seed and oil yields, simultaneously possessing high resistance to the Orobanche population of races distributed in Bulgaria. In 2002, the hybrid Rada was registered for testing by State Variety Testing Commission and it exceeded the mean standard of the country. The combined use of interlinear hybridization with physical mutagenesis or ultrasound and the embryo culture method leads to increased genetic variability in sunflower and to a considerable shortening of the breeding process, producing 5 generations within a single year.

Accessions from different Helianthus species, cultivated sunflower forms and interspecific hybrid forms and lines were included in this investigation. It was established that broomrape resistance was transferred from 11 perennial Helianthus species to interspecific hybrids developed on the basis of new sunflower lines. Some of the new lines possessed other desirable agronomical characters, which could be successfully transferred to new sunflower hybrid cultivars. Differences were observed in the origin of broomrapes found in different locations of northern Bulgaria. Diverse origin of some of the obtained sunflower forms was confirmed using the RAPD analysis.