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.

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.

To evaluate the agro-biological traits and select the promising populations of alfalfa under pedoclimatic conditions, field experiments were carried out in two locations of the Lithuanian Research Centre for Agriculture and Forestry (western Lithuania 55°70′ N, 21°49′ E and central Lithuania 55°23′ N, 23°51′ E). Eleven populations were established in acidic soil with a pH of 4.0 (experimental site I) and neutral soil with a pH of 7.0 (experimental site II). The productivity and agro-biological traits: fresh matter yield, dry matter yield, seed yield, stem thickness, and stem, leaf, and inflorescence weight of alfalfa populations were evaluated from 2019 to 2021. In the acidic soil, the populations 3056, 3132, 3130, and 3058 yielded more fresh and dry matter compared to the standard cultivar Birutė in the period from 2019 to 2021. In the acidic soil, populations 3131 and 3057 had a higher seed yield compared to the cultivar Birutė in 2019 and 2020, respectively. The 3086 population significantly differed in leaf weight compared to the cultivar Birutė. The cultivar Birutė and population 3132 were similar in stem thickness and fresh matter yield. In the neutral soil, population 3056 yielded more fresh matter compared to the cultivar Birutė.