The use of biofertilizers is important for sustainable agriculture, and the use of nodule bacteria and endophytic actinomycetes is an attractive way to enhance plant growth and yield. This study tested the effects of a biofertilizer produced from Bradyrhizobium strains and Streptomyces griseoflavus on leguminous, cereal, and vegetable crops. Nitrogen fixation was measured using the acetylene reduction assay. Under N-limited or N-supplemented conditions, the biofertilizer significantly promoted the shoot and root growth of mung bean, cowpea, and soybean compared with the control. Therefore, the biofertilizer used in this study was effective in mung bean, cowpea, and soybean regardless of N application. In this study, significant increments in plant growth, nodulation, nitrogen fixation, nitrogen, phosphorus, and potassium (NPK) uptake, and seed yield were found in mung beans and soybeans. Therefore, Bradyrhizobium japonicum SAY3-7 plus Bradyrhizobium elkanii BLY3-8 and Streptomyces griseoflavus are effective bacteria that can be used together as biofertilizer for the production of economically important leguminous crops, especially soybean and mung bean. The biofertilizer produced from Bradyrhizobium and S. griseoflavus P4 will be useful for both soybean and mung bean production.

The decline in rice yields as a result of excessive chemical fertilizer (CF) inputs is a matter of great concern in rice-growing regions of Asia. In two-year’s field experiments, the nitrogen, phosphorus, and potassium (NPK) status, growth characteristics and yield of rice were examined by application of poultry manure (PM), cow manure (CM) and compost (CP). Organic fertilizers were applied as EMN (estimated mineralizable N) based on their total N content. Six treatments were assigned in a randomized complete block design: (1) no-N fertilizer (N₀); (2) 50% CF (CF₅₀), (3) 100% CF (CF₁₀₀); 50% CF + 50% EMN from (4) PM or (5) CM or (6) CP. Compared with CF₁₀₀, the CF₅₀PM₅₀ (total N ≥ 4%) accumulated higher N, P and K content in leaf, sheath, panicle and seeds, resulting in greater growth and yield. The CF₅₀PM₅₀ increased yield by 8.69% and 9.70%, dry matter by 4.76% and 5.27% over CF₁₀₀ in both years. The continuous application of CF₅₀CM₅₀ (total N < 4%) and CF₅₀CP₅₀ (total N < 4%) treatments led to similar NPK contents but higher yields than those of CF₁₀₀ treatment in 2018. In conclusion, the organic fertilizer (total N ≥ 4%) with the EMN method enhances higher N availability in each year. Continuous application of organic fertilizer (total N < 4%) over two years effectively increased N availability in the second year. The 50% organic fertilizer (total N ≥ 4%) and 50% CF led to increased NPK availability and rice yields over the 100% CF treatment, reducing CF usage and leading for sustainable agriculture.

Co-inoculation of nitrogen-fixing bacteria with plant growth-promoting bacteria has become more popular than single inoculation of rhizobia or plant-growth-promoting bacteria because of the synergy of these bacteria in increasing soybean yield and nitrogen fixation. This study was conducted to investigate the effects of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 co-inoculation on plant growth, nodulation, nitrogen fixation, nutrient uptake, and seed yield of the ‘Yezin-6’ soybean cultivar. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Uptake of major nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] was also measured. This study showed that single inoculation of SAY3-7 significantly increased shoot biomass; nodulation; Relative Ureide Index (RUI %), percent nitrogen derived from N fixation (% Ndfa); N, P, K, Ca, and Mg uptakes; during the later growth stages (R3.5 and R5.5), compared with control. These observations indicate that SAY3-7 is an effective N-fixing bacterium for the plant growth, nodulation, and nitrogen fixation with an ability to compete with native bradyrhizobia. Co-inoculation of SAY3-7 and P4 significantly improved nodule number; nodule dry weight; shoot and root biomass; N fixation; N, P, K, Ca, and Mg uptake; at various growth stages and seed yield in ‘Yezin-6’ soybean cultivar compared with the control, but not the single inoculation treatments. Significant differences in plant growth, nodulation, N fixation, nutrient uptake, and yield between co-inoculation and control, not between single inoculation and control, suggest that there is a synergetic effect due to co-inoculation of SAY3-7 and P4. Therefore, we conclude that Myanmar Bradyrhizobium strain SAY3-7 and P4 will be useful as effective inoculants in biofertilizer production in the future.

This study was conducted to evaluate the effects of Bradyrhizobium japonicum SAY3-7, Bradyrhizobium elkanii BLY3-8, and Streptomyces griseoflavus P4 on the symbiotic effectiveness of soybeans before biofertilizer production, to produce biofertilizer containing the studied three strains (SAY3-7, BLY3-8, and P4), to test the effectiveness of the biofertilizer on soybean varieties, and to assess the varietal effects and interaction effects between variety and biofertilizer on plant growth, nodulation, nitrogen fixation, nutrient absorption, and seed yield. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Contents of nutrients (N, P, K, Ca, and Mg) were also measured to calculate their uptakes. In this study, synergistic effects of nitrogen fixation were induced by combined inoculation with SAY3-7, BLY3-8 and P4 in all tested soybean varieties. Therefore, we assumed that an effective biofertilizer could be produced using these effective bacteria (SAY3-7, BLY3-8, and P4). After making biofertilizer using these effective bacteria, packages were stored at 30 °C. The populations of the bacteria in the biofertilizer were maintained at a density of 1 × 10⁸ colony forming units (cfu) g⁻¹ for P4 and 7 × 10⁹ cells g⁻¹ for Bradyrhizobium. Diluting biofertilizer by 10⁻³ proved more effective for nodulation and nitrogen fixation than other dilution treatments. Moreover, this biofertilizer significantly promoted plant growth, nodulation, nitrogen fixation, nutrient uptakes, and seed yield in Yezin-3 and Yezin-6 soybean varieties. Yezin-6 is a more efficient variety than Yezin-3 for improved plant growth, nodulation, nitrogen fixation, nutrient absorption, and seed yield. Taken together, the application of an effective biofertilizer and the use of an efficient soybean variety can play important roles in promoting plant growth, nodulation, nitrogen fixation, and higher seed yield.

Rhizobia play an important role in plant nutrition by fixing nitrogen that is subsequently available for uptake by plants. In Myanmar, it has been difficult to characterize the nitrogen-fixing indigenous bradyrhizobia strains. In this study, 120 strains were isolated from five major soybean-growing regions of Myanmar. The strains were characterized based on sequence analysis of the 16S-23S rRNA internal transcribed spacer (ITS) region. Determination of nodulation types of native isolates was based upon their compatibility between strain and soybean cultivars by inoculation test. Our goal was to describe the polygenetic diversity among indigenous bradyrhizobial strains isolated from Myanmar and to identify their nodulation types. Sequence analysis indicated that all isolates belonged to the Bradyrhizobium genus and were conspecific with B. liaoningense,B. elkanii,Bradyrhizobium spp., B. japonicum and B. yuanmingense. A phylogenetic tree showed that 40, 33.3, 19.2, 5 and 2.5% of the isolates were related to B. liaoningense,B. elkanii,Bradyrhizobium spp., B. japonicum and B. yuanmingense, respectively. These results suggested that B. liaoningense and B. ellkanii were the predominant Bradyrhizobium species present in Myanmar soils.B. elkanii, B. liaoningense and Bradyrhizobium spp. strains were dominant in acid soils, slightly acid to slightly alkaline soils and alkaline soils, respectively. Among tested isolates, Type A strains accounted for 74% of the isolates, while Type B and C strains accounted for 22 and 4%, respectively.It can be concluded that the diversity and distribution of indigenous bradyrhizobia differed markedly among sampling sites and among sites within the same region, and were affected by soil pH and climate. Determination of nodulation types of indigenous brayrhizobia provides useful information for selection of strains compatible with different soybean cultivars. This is the first report describing B. liaoningense strains isolated from soybean in Myanmar. Key words: Indigenous bradyrhizobia, internal transcribed spacer (ITS), Myanmar, phylogenetic diversity, soybean, nodulation type.

Chickpea (Cicer arietinum L.) is one of the world’s main leguminous crops that provide chief source of food for humans. In the present study, we characterized thirty isolates of indigenous chickpea rhizobia from Myanmar based on the sequence analysis of the bacterial 16S rRNA gene. The sequence analysis confirmed that all isolates were categorized and identified as the genus Mesorhizobium and they were conspecific with M. plurifarium, M. muliense, M. tianshanense, and M. sp. This is the first report describing M. muliense, M. tianshanense, and M. plurifurium from different geographical distribution of indigenous mesorhizobia of chickpea in Myanmar. In order to substitute the use of chemical fertilizers in legume production, there is a need for the production of Biofertilizers with rhizobial inoculants. The effectiveness of Myanmar Mesorhizobim strains isolated from soil samples of major chickpea growing areas of Myanmar for plant growth and nitrogen fixation were studied in pot experiments. The nodule dry weight and acetylene reduction activity of the plant inoculated with Mesorhizobium tianshanense SalCP19 was significantly higher than the other tested isolates in Yezin-4 chickpea variety. But, Mesorhizobium sp. SalCP17 was showed high level of acetylene reduction activity per plant in Yezin-6 chickpea variety.