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.

Oat (Avena sativa L.) is a crop of significant economic and nutritional importance; however, its yield and quality can be substantially reduced by fungal diseases, including powdery mildew caused by Blumeria graminis f. sp. avenae (Bga). The aim of this study was to evaluate the phenotypic resistance of 110 genotypes of Lithuanian oat cultivars to powdery mildew using five pathogen isolates. Based on the results obtained, three genotypes with the highest level of resistance were selected. Among them, one cultivar—Delfin—carries the Pm7 resistance gene, as documented in the literature. The two remaining genotypes were subjected to detailed evaluation using 30 isolates for the purpose of resistance gene postulation, followed by molecular analysis employing STS (Sequence-Tagged Sites) and SCAR (Sequence Characterized Amplified Region) markers, aimed at identifying the presence of the Pm4, Pm5 and Pm7 genes, considered among the most desirable resistance genes against powdery mildew in oat. None of these genes were confirmed in the studied cultivars. The results obtained suggest that the observed resistance may be conferred by other as-yet-unidentified resistance genes. The studied genotypes may therefore represent a novel and valuable source of resistance to powdery mildew, useful in breeding programs aimed at improving disease resistance in oat.