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.

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Carduus acanthoides L (spiny plumeless thistle) a biannual wild species with 2n = 22 chromosomes was crossed with Helianthus annuus L. When crossing, pollen from C. acanthoides germinated and pollinated the stigmas of sunflower lines HA 89A after 48 h. The crossability rate was low, but seeds and hybrid plants were obtained. The F1 plants strongly resembled the cultivated sunflower with the most important bio-morphological characters, even though they had an intermediate type of heritability. The hybrid nature was confirmed by RAPD markers. The polymorphism between H. annuus, C. acanthoides, and their F1 hybrids was studied using RAPD. The result showed introgression of C. acanthoides in the hybrid progeny. It was established that the wild species carried Rf genes for the CMS PET-1. After self-pollination and sib-pollination of the F1 plants and back-crossing with cultivated sunflower, F2, BC1 and next generation hybrid progenies were obtained. The investigation encompassed the period 2000–2007 and 2014–2018. Some of the new lines have been included in a heterosis breeding program for developing hybrids for the sunflower market.

New traits that are useful for the cultivated sunflower can be received by applying classical breeding methods. A new form sunflower that is resistant to herbicides Pulsar and Express was obtained by hybridization between the sunflower mutant M-95-674 and the line HA 425. Test results from the period 2017–2019 confirm the resistance to both herbicides. This resistance can be transferred into other classical selected lines.

The amount and quality of yields depend on the successful protection of crops from diseases, pests, weeds, and abiotic factors. The sunflower is a plant in which most diseases and pests are overcome genetically. The chemical method is also used in the production of sunflower, but it is important to say that there are still no genetically modified (GM) sunflowers on the market. By applying the classical breeding methods, new sunflower elite inbreed B lines that are resistant to two classes of herbicides (imidazolinones and sulfonylureas) were received. The aim of this study is to summarize the knowledge of pesticides and their use, as well as the breeding methods and resistance to herbicides in the sunflower.