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The aim of the study is to determine the variability of morphological characters for the vegetative development of perennial ryegrass collection and to make a selection of genotypes for different directions of use - for fodder and ornamental purposes. During the period 2015-2018 in the Institute of Forage crops - Pleven a collection nursery was studied in fi eld non-irrigated conditions on leached black soil, in block method, in 2 replications of a total of 21 accessions of perennial ryegrass, with 50 individual plants each (15 varieties and 6 ecotypes, 11 tetraploid and 10 diploid, from Bulgaria, Belgium, Romania and China). Mean, minimum, maximum values, standard deviations and variation coefficients for plant height, tuft width at base and top, habitus, number of leaves, leaf length and width, stem thickness, stem number were present. A great genetic diversity was found in the morphological features of the perennial ryegrass collection accessions, both between them and within population. Highest values of variation coefficients (CV) were obtained for plant stems - 43.05%, habitus - 33.85%, leaf length and width - 25.43% and 26.16%, respectively. In the collection the tetraploid varieties have higher plants, longer and broader leaves and more upright habitus, which ensures higher productivity of fodder and for ornamental and amenity purposes are suitable diploid varieties and ecotypes, with lower plants, short and narrow leaves. [ABSTRACT FROM AUTHOR]

During the 2006-2009 period, in the experimental field of the Institute of Forage Crops in Pleven a study was conducted with the purpose of determining the effect of cultural practice and weed control on the seed productivity of perennial ryegrass. As a result of the four-year study, the following conclusions were made: Perennial ryegrass is very susceptible to the weed competitive influence in the establishment year, as well as in the seed production years. The highest efficiency against the weeds was obtained by chemical control, but the use of cover crops (spring forage pea, spring barley) and mixed stands with white clover are a successful alternative practice with weed suppressive and ecological effects under the conditions of ecologically friendly agriculture. On average for the period of the study, the seed yield of perennial ryegrass exceeded that from the check of the pure stand as follows: pure stands with chemical control - by 27%; stands with cover crops and chemical control - by 20 to 32%, the same stands without chemical weed control - by 5 to 11%; mixed stands with chemical control - by 30% and without weed control - by 14%. Considerable dry biomass yield was harvested from the seed production stands of perennial ryegrass and in the establishment year the sowing of a cover crop or in a mixed stand resulted in more efficient use of the area and an yield increase by 3.7 to 13.9 times, and on average for the four-year period - by 30 to 59%. [ABSTRACT FROM AUTHOR]