Selective background for forming the source alfalfa material with high adaptive and symbiotic abilities

Based on the results of research conducted in 2022–2023, it was hypothesized that in order to create highly adaptable alfalfa varieties and complementary strains of nodule bacteria that can be used in new alfalfa-growing regions characterized by a lack of heat and sunny days, as well as excessive moisture availability, their testing and selection should be conducted in vegetative experiments in February-April and September-November at lower air temperatures and lower light levels. The test of alfalfa varieties and nodule bacteria strains was conducted in a polycarbonate greenhouse from August 2024 to May 2025. During the period from August 5 to November 5, alfalfa-rhizobial symbiotic systems with varying degrees of efficiency were formed. The winter hardiness of highly effective symbiotic pairs with different alfalfa varieties was 19.0-48.1%, while the winter hardiness of plants that did not form an effective symbiosis was 1.0–2.3%. The average productivity of overwintered plants of highly effective symbiotic pairs reached 36.6–111.4 g/plant of dry matter and 3.00–6.99 g/plant of seeds. The corresponding indicators of alfalfa plants that did not enter into an effective symbiosis were 28.1–49.20 and 2.13–2.62 g per plant. The most winter-hardy systems were alfalfa-rhizobial systems with the varieties Vega 87 (36.1%) and Taisiya (48.1%), and the most productive systems were with the varieties Lyusya and Taisiya (96.7 and 111.4 g of dry matter per plant, as well as 6.21 and 6.99 g of seeds per plant). The most effective strains of nodule bacteria, L6-1, L6-3, and A1, increased plant productivity in 2.3–2.9 times by dry matter and in 2.6–3.3 times by seeds.