Creation of the Hay-Pasture Type Breeding Populations of Red Clover for the Conditions of Northern Bulgaria

In a field experiment conducted in the period 2019–2021, breeding populations of red clover were studied from the first to the third vegetation. They represent families – half-sib offspring of elites selected from local and breeding populations, as well as from populations representing Syn 1 and Syn 2 generation from the subspecies crossing of T. pratense ssp. nivale × T. pratense ssp. pratense. The aim is to evaluate the selection progress according to criteria significant for the combined use of the species, namely high and stable productivity over the years during secondary (summer) regrowing, as well as the related values of basic morphological traits, which are components of forage yield. According to the obtained results, the number of generative stems formed by a plant during summer regrowing, as well as a stable performance of leaf area by regrowths and years are the morphological characteristics associated with high productivity during summer regrowing, respectively suitability for combined use. The population with spreading phenotype TPNpr, Syn 2 generation of the subspecies crossing T. pratense ssp. Nivale × T. pratense ssp. pratense has the highest selection value in the specified direction. It stands out with the highest summer productivity and persistence over a three-year period of use.