Comparison of the adaptive potential for Rhizobium leguminosarum bv. viceae nodule bacterial populations isolated in natural ecosystems and agrocenoses

摘要

Polymorphism analysis was performed in Rhizobium leguminosarum bv. viceae populations isolated from geographically distant regions of Ukraine and Middle Asia. Examination of cultural, biochemical, and symbiotic traits revealed interpopulation differences, which were attributed to the difference in conditions between natural ecosystems and agrocenoses. Vetch has high species diversity and is not cultivated in Middle Asia, and the corresponding rhizobial population displayed higher genetic diversity and higher polymorphism of adaptive traits ensuring saprophytic development in soil and the rhizosphere, including melanin synthesis (35%) and active exopolysaccharide production (90%). Strains of the Ukrainian population had a lower exopolysaccharide production (10%), did not produce melanin, had higher herbicide resistance, and utilized glucose and succinate (main components of plant root exudation) as carbon sources. Strains capable of efficient symbiosis with Vicia villosa Roth. had a higher frequency in the Middle Asian than in the Ukrainian population, especially among strains isolated from soil (80 and 35%, respectively). In addition, strains of the Middle Asian population better competed for nodulation. It was assumed that the formation of rhizobial populations in vetch cultivation regions (Ukraine) is aimed at adaptation to ectosymbiotic (rhizospheric) interactions with plants and anthropogenic stress factors, while strains of the vetch original center (Middle Asia) are mostly adapted to the endosymbiotic interaction and to natural edaphic stress factors.