The uneven effectiveness of rhizobia inoculants has increased interest in developing specific inoculants for each genotype. This study investigated the biological nitrogen fixation efficiency and competition between different Rhizobium leguminosarum strains in different pea genotypes, namely, “Egle DS” and “Respect”. The results showed that plant genotype was a significant factor determining competition and nitrogen fixation among R. leguminosarum strains. The most competitive R. leguminosarum LIN06 strain in the pea genotype “Egle DS” was characterized by a low nitrogen fixation efficiency, while the most competitive R. leguminosarum EGLE10 strain in the “Respect” genotype was characterized by a high biological nitrogen fixation efficiency. It was also found that the “Respect” genotype may prefer and form symbiotic relationships with more efficient nitrogen fixing strains, while the “Egle DS” genotype formed symbiotic relationships with less efficient strains. However, even less efficient strains had a significant positive effect on nitrogen accumulation in plants under natural conditions. Finally, our study showed that sophisticated tests and methods are not necessary to analyze the competitiveness of rhizobia; it is sufficient to analyze the effectiveness of bacterial strains on plants in unsterilized soil.

The benefits of cereal-legume mixed cropping is a sustainable agricultural practice. However, knowledge of the genotypic differences of semi-leafless pea varieties is not enough to help them compete with cereals. In this study, the effects of Lithuania’s newest Pisum sativum cultivars (‘Egle DS’ and ‘Lina DS’) and, for comparison, a control cultivar (‘Jūra DS’) established with Avena sativa in mixed cropping system were investigated. Three years of field trials (2018, 2019 and 2020) with four experiments involved three different mixtures of each field pea cultivar with oat. The aboveground biomass of mixed cropped new field pea cultivars was found to be significantly higher: biomass of cultivars ‘Egle DS’ increased by 17.0% and ‘Lina DS’ by 7.2% on average compared with the control cultivar ‘Jūra DS’. For the mixed cropping system, statistically greater total aboveground biomass was observed with plant ratios of 50% pea + 50% oat and 60% pea + 40% oat compared to peas monocultures. Mixed cropped oat was the dominant species in all tested mixture compositions; however, the highest total grain yield of mixed crops was obtained when new pea ‘Lina DS’ and ‘Egle DS’ cultivars were included in the mixtures compared with the control cultivar. The new pea cultivar ‘Egle DS’ had a greater effect on protein content compared to other tested pea cultivars. In the new pea cultivars ‘Lina DS’ and ‘Egle DS’, the higher photosynthetic capacity and aboveground biomass of mixed cropped pea with oat showed mixture effects in the mixed cropped system and could increase total yield compared with pea monoculture. Generally, the new pea cultivars displayed a greater Land Equivalent Ratio (LER) value, resulting in the greatest yield among the mixtures on average for all three years and all four experiments. Future research could optimize the effects of pea cultivar mixtures with cereals to further improve the yield of organic mixed cropping systems.

This study aimed to evaluate and compare the physiological traits, productivity, and seed quality of nine faba bean varieties grown in a field trial under the Boreal climate conditions. A two-factor field experiment was laid out in a split-plot design: The seeds in the main plots were sown and treated with seed fungicide (SF) and untreated (without SF) (factor A). The sub-plots were assigned to nine varieties (factor B). The physiological traits of faba bean significantly varied among the varieties, and the behavior of faba bean varieties differed between the two growing seasons. The values of physiological traits for varieties Julia and Boxer significantly surpassed the trial mean under wet conditions, while the trait values for Fuego and Bioro were surpassed under conditions of a lack of moisture. Fungicidal seed treatment had a negligible effect on the physiological traits, while it had a significant negative influence on the leaf area index at the beginning of the flowering stage. SF had a noticeable effect on seed yield only for the varieties Nida DS and Fuego. The findings of the study revealed that Fuego and Isabell were the most suitable faba bean varieties for cultivation in the Boreal climate zone as they were distinguished from the other tested ones by the highest seed yields.

Biological nitrogen fixation in legume plants depends on the diversity of rhizobia present in the soil. Rhizobial strains exhibit specificity towards host plants and vary in their capacity to fix nitrogen. The increasing interest in rhizobia diversity has prompted studies of their phylogenetic relations. Molecular identification of Rhizobium is quite complex, requiring multiple gene markers to be analysed to distinguish strains at the species level or to predict their host plant. In this research, 50 rhizobia isolates were obtained from the root nodules of five different Pisum sativum L. genotypes (“Bagoo”, “Respect”, “Astronaute”, “Lina DS”, and “Egle DS”). All genotypes were growing in the same field, where ecological farming practices were applied, and no commercial rhizobia inoculants were used. The influence of rhizobial isolates on pea root nodulation and dry biomass accumulation was determined. 16S rRNA gene, two housekeeping genes recA and atpD, and symbiotic gene nodC were analysed to characterize rhizobia population. The phylogenetic analysis of 16S rRNA gene sequences showed that 46 isolates were linked to Rhizobium leguminosarum; species complex 1 isolate was identified as Rhizobium nepotum, and the remaining 3 isolates belonged to Rahnella spp., Paenarthrobacter spp., and Peribacillus spp. genera. RecA and atpD gene analysis showed that the 46 isolates identified as R. leguminosarum clustered into three genospecies groups (B), (E) and (K). Isolates that had the highest influence on plant dry biomass accumulation clustered into the (B) group. NodC gene phylogenetic analysis clustered 46 R. leguminosarum isolates into 10 groups, and all isolates were assigned to the R. leguminosarum sv. viciae.

Field pea (Pisum sativum L.) is one of the most important grain legumes in European agriculture, having many benefits for agro-ecosystems and also one of the lowest carbon footprints of any crop. However, this crop has many more drawbacks when grown organically as opposed to conventionally. Therefore, our study aims to investigate the performance of newly bred field pea varieties and to test their differences of adaptivity to organic and conventional farming systems. Our study evaluated productivity, as well as the biological and nutritional parameters of the following four new field pea varieties: Lina DS, Egle DS, Ieva DS and Jura DS, all cultivated in the Nemoral climatic zone, where field peas are widely produced. The performance was compared with the long-term standard field pea variety Ingrid. Our study showed that all investigated new varieties had higher productivity compared to the long-term standard Ingrid. The organic cropping system limited the grain yield of field pea, and different varieties tended to respond differently to this type of crop management. Therefore, different varieties should be selected and suggested for organic and conventional cropping systems. Furthermore, with various different responses to the precipitation level, different varieties could be suggested for farming in different regions. The nutritional value (content of proteins and amino acids) also responded significantly to the management system and the selection of field pea variety. Newly bred variety Egle DS demonstrated the highest grain yields, and the highest content of proteins and essential amino acids in the seeds of field pea grown in an organic farming system. Egle DS accumulated 30 percent higher content of arginine compared to the standard variety.