Rhizobium Inoculation Enhances the Resistance of Alfalfa and Microbial Characteristics in Copper-Contaminated Soil

Some studies have reported the importance of rhizobium in mitigating heavy metal toxicity, however, the regulatory mechanism of the alfalfa-rhizobium symbiosis to resist copper (Cu) stress in the plant-soil system through biochemical reactions is still unclear. This study assessed the effects of rhizobium (Sinorhizobium meliloti CCNWSX0020) inoculation on the growth of alfalfa and soil microbial characteristics under Cu-stress. Further, we determined the regulatory mechanism of rhizobium inoculation to alleviate Cu-stress in alfalfa through plant-soil system. The results showed that rhizobium inoculation markedly alleviated Cu-induced growth inhibition in alfalfa by increasing the chlorophyll content, height, and biomass, in addition to nitrogen and phosphorus contents. Furthermore, rhizobium application alleviated Cu-induced phytotoxicity by increasing the antioxidant enzyme activities and soluble protein content in tissues, and inhibiting the lipid peroxidation levels (i.e., malondialdehyde content). In addition, rhizobium inoculation improved soil nutrient cycling, which increased soil enzyme activities (i.e., β-glucosidase activity and alkaline phosphatase) and microbial biomass nitrogen. Both Pearson correlation coefficient analysis and partial least squares path modeling (PLS-PM) identified that the interactions between soil nutrient content, enzyme activity, microbial biomass, plant antioxidant enzymes, and oxidative damage could jointly regulate plant growth. This study provides comprehensive insights into the mechanism of action of the legume-rhizobium symbiotic system to mitigate Cu stress and provide an efficient strategy for phytoremediation of Cu-contaminated soils.

Effects of Tiba and Rhizobium Application on Growth, Yield and Biochemical Components of Brri Dhan-55 (Oryza Sativa L.)

Effects of TIBA (10, 25, 50 ppm) and Rhizobium inoculation on growth, yield and biochemical components of BRRI Dhan-55 were investigated. Results showed that application of 10 ppm TIBA produced tallest plant, higher number of tillers and leaves per plant although statistically identical to control. The Rhizobium and TIBA treatments had mostly retarding effects on dry weight of leaves, shoots and roots where the lowest values was obtained from Rhizobium application. Leaf area ratio was positively affected by TIBA and Rhizobium treatments except due to 10 ppm where, significantly maximum value was noted from Rhizobium treatment. Specific leaf weight, relative growth rate and net assimilation rate were negatively responded following all treatments and the least value was also recorded from Rhizobium treatment in each cases. Yield attributes and yield of BRRI Dhan-55 were both positively and negatively influenced by Rhizobium and TIBA treatments. The highest harvest index was found in Rhizobium treated plants. The only increase in yield per plant due to 10 ppm TIBA was 2.48 % over the control but statistically similar to control. Results showed that Rhizobium inoculation had showed lowest value in protein content of leaves and seeds. Application of TIBA treatments had significant positive effects on protein content of leaves at flowering stage. However, the influence was rather negative at both tillering and grain filling stages. The 25 ppm TIBA resulted significantly maximum protein content of seeds followed by 10 ppm. Bangladesh J. Bot. 50(4): 1181-1189, 2021 (December)

Exploring the Role of Mycorrhizal and Rhizobium Inoculation with Organic and Inorganic Fertilizers on the Nutrient Uptake and Growth of Acacia mangium Saplings in Acidic Soil

Strong and healthy saplings are a prerequisite to establish a successful forest. Therefore, an attempt has been made to develop the best package for nutrient supplementation to raise healthy Acacia mangium saplings, especially in acidic soil. The seeds were sown in pots, receiving different combinations of Arbuscularmycorrhizal (AM), Rhizobium inoculation with application of lime, and mustard oil cake (MOC). The highest spore count and infection percentage (3220 kg−1 soil and 69) were recorded in the AM + MOC + R treated pot, whereas the lowest (2553 kg−1 soil and 37) were recorded in the AM + L treated pot. Nitrogen concentration and uptake in the sapling were higher in the Rhizobium-inoculated treatments than the uninoculated ones. The sulfur concentration and uptake were higher in the MOC-supplemented treatment. Similarly, the P, K, Ca, and Mg concentrations and uptakes were higher in the limed treatments than the unlimed ones. The micronutrient concentration and uptake were higher in the unlimed treatments compared to the lime practice. The concentration of N in Rhizobium-treated pots, P and K in lime-treated pots, and S in MOC-treated pots were increased, whereas the soil pH decreased in all treatments except in the integrated package (AM + MOC + R + L) after 120 days. The Ca and Mg were reduced in all treatments, whereas micronutrients were reduced in all packages except the control. Under different nutrient management practices, plant height and stem girth continuously increased by 9.5 to 12 cm and 3 to 4 times, respectively. The production of robust saplings required integrated application of lime, MOC, AM, and Rhizobium in an acid soil that facilitated better root growth with availability of adequate nutrients for saplings.

Rhizobium inoculation enhanced the resistance of alfalfa and soil enzymatic activity in Cu-polluted soils

Although some studies have reported an important role of rhizobia in mitigating heavy metal toxicity, the regulatory mechanism of the alfalfa-rhizobium symbiosis system to resist copper (Cu) stress through biochemical reactions in the plant-soil system is still unclear. Hence, this study assessed the effects of rhizobium inoculation (i.e., Sinorhizobium meliloti CCNWSX0020) on the growth of alfalfa and soil enzyme activities under Cu stress. Our results showed that rhizobium inoculation markedly alleviated Cu-induced growth inhibition by increasing chlorophyll content, height and biomass and the contents of nitrogen and phosphorus in alfalfa. The content of malondialdehyde (MDA) was increased in both shoot and root of alfalfa under Cu stress. The application of rhizobium alleviated Cu-induced phytotoxicity by increasing the activity of antioxidant enzymes and soluble protein content of tissues and inhibiting the level of lipid peroxidation (i.e., MDA level). In addition, rhizobium inoculation improved soil nutrient cycling, increased soil enzyme activities (i.e., β-glucosidase activity and alkaline phosphatase) and microbial biomass nitrogen. Both Pearson correlation coefficient analysis and partial least squares path modeling (PLS-PM) identified that the interactions between soil nutrient content, enzyme activity, microbial biomass and plant antioxidant enzymes and oxidative damage could jointly regulate plant growth. This study provides comprehensive insights into the mechanism of action of the legume-rhizobium symbiosis system to mitigate Cu stress and provide an efficient strategy for phytoremediation of Cu-polluted soils.

Effect of P Application Rate and Rhizobium Inoculation on Nodulation, Growth, and Yield Performance of Chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) is the world’s third most vital food legume after beans and peas in production level. Yet, its productivity in the last decade has been declined, and it has been contended that the usual native soil rhizobial populations are insufficient/ineffective in N2-fixation. Rhizobium inoculation of the seed may substitute costly N-fertilizers and provide a useful way of achieving sustainable production. Hence, to supply an adequate rhizobial population in the rhizosphere, seed inoculation of chickpea with an effective and importunate rhizobial strain is essential in soils having no/feeble bacterial existence and has revealed optimistic effect on nodule number and mass, growth, yield, and its attributes over uninoculated ones. Its effect has been influenced by N content and P-deficiency of soil, rhizobium strain, variety, T°, pH, salinity, and moisture stress. Phosphorus (P) demand is high in chickpeas, and P deficiency also has a negative effect on chickpea production success. Several research results revealed significant effects of P rate (30–200 kg P2O5 ha−1) on nodule number, mass, and rating plant−1; LAI, RGR, DM, plant height, and branches plant−1; pods and grains plant−1, grain and biomass yields, 100-grain weight, and HI compared to the control. P rates response has been affected by moisture level, pH, available P and N, and variety. Particularly, joint use of P rate and rhizobium inoculation on chickpea has been stated to improve nodulation, growth, and yield and soil fertility. Various studies on the integrated use of P rate and rhizobium inoculation under varying situations showed enhanced nodulation, growth, and yield over the P rate or rhizobium inoculation alone. This might be attributed to adequate P supply and improved utilization with the provision of suitable N2-fixing bacteria for enhanced nodulation and adequate N supply.

Rhizobium inoculants suppress emergence of the weed Striga gesnerioides in cowpea

Cowpea is a grain legume of major importance in sub-Saharan Africa where it is cultivated by smallholder farmers on poor soils and production is often constrained by the parasitic weed Striga gesnerioides. Experiments were conducted to assess the potential of rhizobium inoculation in mitigating Striga infestation and increasing cowpea productivity. We tested under basal P application and artificial S. gesnerioides inoculation the impact of cowpea genotypes (G) (nine Striga-resistant and 11 Striga–susceptible genotypes) and bradyrhizobium inoculation (N) (two bradyrhizobium strains USDA3384 and IRJ2180A, and uninoculated control) on Striga dynamics and cowpea yield. Additional treatments included N supplied as urea (with and without), and no input (i.e., soil inherent N and P) that served as negative check. A first experiment was carried out in potted sterile soils in the screen house excluding addition of N-fertilizers. Significant G x N interactions were observed in counts of nodule (P = 0.012), Striga attachment (P < 0.0001) and emergence (P = 0.005), and cowpea shoot growth (P = 0.016). Cowpea nodulated poorly across host lines, Striga counts were the lowest for resistant varieties with no emerged plants. Rhizobial inoculants depressed Striga counts with consistent differences found across cowpea genotypes. Inoculation with IRJ2180A performed the best against Striga attachment in resistant genotypes, and its emergence in susceptible genotypes. In the field trial, nodule numbers were lowest in cowpea without inputs (P < 0.0001). The G x N interaction was significant in emerged Striga plants (P < 0.0001). Resistant genotypes were free of emerged Striga while for susceptible ones, Striga emergence was the highest without any input addition. Significant G x N interaction was observed in cowpea grain yield (P < 0.0001). Yield response to inoculation was most obvious for resistant genotypes inoculated with the strain IRJ2180A (P = 0.0043). The integrated use of Striga-resistant cowpea lines and elite bradyrhizobium inoculant under moderate application of P-based fertilizer could be a promising approach for mitigating Striga infestation and increasing productivity.

Effects of Different Biofertilizer on Soybean (Glycine max) Production

The experiment was conducted in the agriculture field of the International University of Business Agricultural and Technology (IUBAT), Dhaka, from January to June 2017 to find out the effect of different Rhizobium inoculations on soybean production. The experiment was set up in a Completely Randomized Design (CRD) with four replications. Eight Rhizobium inoculations and one control treatment were used in the study to assess the effect of different biofertilizers on soybean production. The findings of the study showed that Strain Bacteria (SB) 316 inoculant performed better in all aspects of growing parameters and yield components like nodulation, vegetative growth, and yield. However, the control treatment performed lowest in every parameter. As a result of the experiment, it could be concluded that Rhizobium inoculation has a significant effect on vegetative growth, nodulation, and yield component of soybean. The SB 316 inoculant has been found as the most effective Rhizobium inoculation in soybean production.

Effect of Integrated Use of Rhizobium Inoculum and Phosphorus Fertilization on Nodulation, Growth, and Yield of Soyabean CV. Binasoybean-2

The experiment was carried out to investigate the effect of rhizobium inoculum and phosphorus fertilization on nodulation, growth, and yield of soyabean cv. Binasoybean-2 at the area of Chamberkella, East Subarnachar Upazila, Noakhali, Bangladesh, from mid-January to first week of May 2018. Four levels of Rhizobium inoculation viz: 0, 25, 50 and 75 g kg-1 and four levels of phosphorus viz: 0, 18, 36 and 54 kg P ha-1 were applied. The experiment was laid out in a randomized complete block design (RCBD) with three replications. The effect of interaction of different combinations of Rhizobium inoculation and phosphorus rates showed regular trend, although their effects on some of studied growth, and yield parameters were insignificant but most of the growth and yield parameters were significant. Among sixteen treatment combinations the highest grain yield (2.217 t ha-1) was obtained from the treatment combination of 50 g kg-1 Rhizobium inoculation and 36 kg ha-1 phosphorus which was statistically identical with 50 g kg-1 Rhizobium inoculation with 18 kg ha-1, the lowest yield (1.367 t ha-1) was recorded with control treatment. Res. Agric., Livest. Fish.8(1): 9-17, April 2021