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The productivity of grasslands and pastures mostly depends on cultivated grass varieties. Festulolium (xFestulolium Asch. & Graebn.) is among the most persistent and productive grasses used in many European countries, especially in adverse environments. The aim of the present research was to study photosynthesis activity and crop yield of local and foreign varieties of festulolium and hybrid ryegrass (Loliumxboucheanum Kunth.) under agro-ecological conditions of Latvia. The most significant indices of photosynthetic activity -- leaf area index (LAI) and net photosynthesis productivity (NPP) -- during growth period till first cut were investigated. Field trials were established on sod-gleyic soil (Luvic Epigleyic Phaeozem (Calcaric) -- WRB 2006), fine sandy loam; fertilizers -- 120 kg ha-1 of N, 78 kg ha-1 of P2O5, and 90 kg ha-1 of K2O. The average NPP for festulolium, hybrid ryegrass and perennial ryegrass varieties varied from 5.63 to 8.29 g m-2 day-1. No positive correlation between NPP and dry matter (DM) yield was established. The average LAI was within the range of 1.94-2.91, and a relationship between LAI and DM was found. [ABSTRACT FROM AUTHOR]

New hybrid grasses have been introduced in Latvia recently. Hybrid ryegrass (Loliumxboucheanum Kunth.), considered an ideal grass for European agriculture, is not sufficiently robust to meet many of environmental challenges that face extensive agriculture in less favoured areas. New opportunities for forage production using intergeneric hybrids between more distantly related ryegrass and fescue species have been identified. Diversity of factors controlling festulolium (xFestulolium Asch. & Graebn.) productivity is discussed in many researches. Using intergeneric hybrids, the identification of major factors controlling productivity and feeding value is complicated because of the numerous traits characteristic of their progenitor species. Parental species traits and potential of intergeneric hybrids have been investigated to determine the main factors that influence grass growth and quality, such as nitrogen fertilization, grazing and cutting management, climatic factors and sward age. The importance and potential of new grass species have been analysed. The main target for introgression has been the introduction of biotic and abiotic stress tolerance from Festuca spp. into Lolium spp. Festulolium can show completely novel characteristics, but mostly they are expressed intermediarily. Some varieties are more like ryegrass and some more like fescue, depending on the breeding effort following the cross. Cultivars of festulolium are promising species of fodder grasses in Latvia. Due to its competitive productivity festulolium may be equally ranked with the main forage grasses such as meadow fescue grown in the climatic zone of Latvia. [ABSTRACT FROM AUTHOR]