Twelve genotypes (varieties, hybrids, mutant and hybrid lines) of sorghum (Sorghum bicolor (L.) Moench) were studied. The objective of the study was to determine the popping performance and to establish the relationships with some biochemical parameters (content of crude proteins, starch, moisture) and grain characteristics (pericarp color, grain width, 1000-grain weight). Popping yield of sorghum grain genotypes was in range 32.0% -72.0%. The highest influence on popping yield had 1000-grain weight (r = 0.831), starch content (r = -0.356), followed by moisture content (r = 0.212) and crude proteins (r = 0.282). It was found that the endosperm of the seeds expanded poorly in most genotypes with white coloring of the pericarp (from 33.3 to 90.1%), while for those with a dark-colored seed pericarp, the expansion was from 50.0% to 160.0%. Mutant line M1 (6282) (dark brown color of the pericarp) and hybrid line 1643 (white color of the pericarp) stood out with relatively better popping characteristics and particle size of popped grains. This study demonstrated one of the qualities of sorghum grain-poppability and opportunities for enrichment of the genetic diversity for the breeding program in this culture.

Abstract. Perennial grass species have many valuable qualities that can be used in solving the problem of producing more feed for livestock. In this regard, four introduced varieties of perennial grasses (Phleum pratense L., Agrostis alba L., Dactylis glomerata L. and Lolium perenne L.) were studied in the conditions of Central Northern Bulgaria. The total amount of green biomass (2011-2013 periods) ranged from 394.93 to 786.13 g m -2 as the arrangement was in the following ascending order: perennial ryegrass, white bentgrass, common timothy and cocksfoot. The digestibility of forage dry matter was from 52.54 to 56.93%. Potential energy feeding value was the highest in cocksfoot and protein feeding value was the highest in ryegrass. Evaluating rank of the general parameters for composition, enzyme digestibility and their arithmetical sum showed that rank 1 belonged to L. perenne, cv. Svyatoshynskiy and rank 2 was obtained for D. glomerata, cv. Horlytsya, followed by P. pratense, cv. Pidhiryanka and A. alba, cv. Halychanka.