Aluminium (Al) toxicity is one of the factors limiting alfalfa (Medicago sativa L.) production on acid soils. This study aimed to determine the Al tolerance of M. sativa in the laboratory and field conditions, and to assess and select the most promising accessions for breeding. The response of M. sativa accessions of different eco-geographical origin to Al was evaluated in Petri dishes with filter paper moistened with different aluminium chloride (AlCl 3 ) concentrations: 0 (control), 1.9, 3.7, 5.6, 7.5 and 16 mM. In the laboratory conditions, the Al tolerance of the accessions was evaluated both in Lithuania (59) and in Ukraine (48). The study found that the accessions of M. sativa significantly differed in Al tolerance at the juvenile growth stage. Al toxicity inhibited seed germination and hypocotyl and root growth, particularly at 7.5 and 16 mM AlCl 3 . The Al tolerance index of germination at 7.5 mM and 16 mM AlCl 3 was by 1.8 and 3.3 times lower, respectively, compared with the control. The tolerance index of root and hypocotyl length of the high-tolerance accessions ranged from 28.0% to 47.0% and from 45.0% to 100%, respectively at 7.5 mM. The seed yield of M. sativa was evaluated in the field conditions in Ukraine only. The 48 accessions were sown in an acid (pH 4.9) soil in 2013 and were assessed in 2014-2016. The M. sativa accessions 'Sevani-1', 'JJ Paso', 'Selection Manfredi' and 'Mongolian colorful hybrid' exhibited high Al tolerance both in the laboratory and field conditions and produced the highest seed yield ranging from 41.2 to 47.9 g m 2 , which was 1.3 times higher compared with the standard 'Synucha'.

Alfalfa exhibits high adaptability to a range of environmental conditions. The aim of this study was to evaluate the agro-biological traits of alfalfa and select its most promising cultivars under different contrasting vegetation seasons. The field experiment was carried out at the Institute of Agriculture of Lithuanian Research Centre for Agriculture and Forestry. In 2016 and 2018, eleven alfalfa cultivars of different origin were established in the Endocalcari Epigleyic Cambisol. In the seasons of 2017–2018 and 2019–2020, the agro-biological traits of alfalfa cultivars were evaluated during winter; at the height of spring regrowth; before flowering at the three cuts; and during the fresh and dry matter yields; we also examined the development of diseases at the three cuts. The cultivar Birutė from Lithuania was distinguished by its wintering, its plant height at spring regrowth, its height before flowering, and its fresh and dry matter yields. The cultivar Timbale from France was distinguished by its wintering, spring regrowth, and its height before flowering. The cultivar Magnat from Romania was distinguished by its height before flowering and the fact that it was less damaged by downy mildew. The cultivars Jõgeva 118, Juurlu, and Karlu from Estonia were distinguished by their wintering and the fact that they were less damaged by diseases. The cultivar Eugenia from Italy was distinguished by the fresh and dry matter yields and the height before flowering.

Alfalfa (Medicago spp.) plays an important role in a farming system and contributes to stabilization of the ecosystem by improving soil physical, chemical and biological properties. However, the use of alfalfa is limited due to its susceptibility to edaphic conditions. The objective of this study was to evaluate the agro-biological traits of alfalfa under different soil conditions. Field experiments were carried out in two locations with optimised management. Agro-biological traits of 46 alfalfa (Medicago sativa L. and M. varia Marth.) accessions of different geographic origin were assessed in a high productivity Endocalcari Epigleyic Cambisol. Although environmental conditions were favourable for alfalfa development and growth, the tested genotypes significantly differed in agro-biological traits: plant height of regrowth in spring and after cuts and at flowering period as well as seed yield. Cultivars from colder climate countries (Estonia, Latvia and Lithuania) were the least affected by the downy mildew. In a low productivity acidic Bathygleyic Dystric Glossic Retisol, the pH had a major influence on the distribution of the root system of alfalfa-grass mixture. During the first experimental year, in the naturally highly acidic soil (pH 3.9), where the mineral nutrition was unfavourable, alfalfa produced longer roots, their diameter and mass were larger than in the soil with a pH of 5.0. In the third year of cultivation, in the naturally highly acidic soil only 9.1% of alfalfa plants had survived. A strong correlation (r = 0.873, P < 0.01) was determined between the amount of alfalfa in the dry matter yield and soil acidity.

The morphological traits of alfalfa under acid soil conditions with different mobile aluminium (Al) concentrations were investigated. The study site was Vėžaičiai Branch of the Lithuanian Research Centre for Agriculture and Forestry, 55°70 N, 21°49 E. The experiment featuring the 30 most Al-tolerant alfalfa accessions (populations and cultivars), determined from laboratory trials was established on a Bathygleyic Dystric Retisol in 2018. In 2019 and 2020, the biological and morphological traits were evaluated: plant regrowth, plant height before flowering, wintering, leafiness, stem thickness, plant vigour, stem density, seed yield and resistance to spring black stem leaf spot. The resistance of alfalfa to mobile Al toxicity was determined using a filter-based screening method of selection cycles C1 and C2. The accessions grown in the soil with mobile Al (20.6–23.4 mg/kg) showed better tolerance to Al toxicity in the cycle C2. The hypocotyl tolerance index of these accessions was better at 8, 16, 32 and 64 mm AlCl3 concentrations in the cycle C2. The correlation analysis showed strong significant positive and negative relationships between the morphological traits. A cluster analysis showed that the accessions, grown in the soil with mobile Al (20.6–23.4 mg/kg) were the most resistant to Al toxicity in the cycle C2. These accessions produced a better seed yield and demonstrated lower values of morphological traits compared to cluster 2. Also, these accessions are considered as tolerant to mobile Al toxicity and might be used as donors in breeding for Al toxicity tolerance.

The ultimate purpose of developing new varieties of Medicago spp. is selection of the initial genetic material characteristics responsible for the stabile yield of dry matter. The greatest shortcomings of conventional methods used to determine herbage yield are labour-consuming cuts and the processing of harvested green matter. The main task of the present studies was evaluation of the genetic material of Medicago sativa L. developed using germplasms received from different regions with an impact on winter hardiness and relations with this trait to other properties of accessions. The experiment was conducted at the Lithuanian Institute of Agriculture (LIA) during 2004-2006. Low winterhardiness highly negatively (r = -0.85*, significant at P = 0.05) correlated with spring re-growth and negatively affected (r = -0.65*) the dry matter yield of the first cut. Effective spring re-growth positively (r = 0.41*) influenced plant height before the 1st cut and medium positively (r = 0.66*) the yield of the 1st cut as well as total yield (r = 0.62). Analysis showed that the influence of winterhardiness on the yield of lines with different resistance was considerable. The least damaged lines yielded on average 8.67 t ha -1 , whereas most severely damaged lines yielded 5.43 t ha -1 or 37.4% less. Plant height before the 1st cut showed a weaker effect than winterhardiness and spring re-growth. Lines with highest differences in height produced a herbage yield whose differen ces varied within 25% for the 1st cut and 17% for total yield. Plant height sequentially decreased at every later regrowth and cutting time. Plants of populations with highest winterhardiness were on average slightly lower than those with poor winterhardiness. The highest plants (97 cm) at the 1st cut were found in populations LIA2104, LIA9//10, LIA2358, LIA 2311 with a medium winterhardiness level. The percentage of dry matter in herbage yield decreased with every cut. The highest decrease of dry matter content (25.4% to 20.3%) was observed in populations with a high winterhardiness. Winterhardiness and spring re-growth were the most effective indirect criteria for selecting high-yielding lines among the initial breeding material of Medicago spp.