Assessment of nifH diversity in rhizobial isolates of different origin and the role of antioxidant in respiratory protection

Rhizobia diversity is considered as one of the most useful resources for bioprospecting due to their symbiotic nitrogen-fixing ability with members of Leguminosae. The highly conserved nature of the nitrogenase reductase gene (nifH) makes it an ideal molecular tool to determine the potential for biological nitrogen fixation in any environment. In the present investigation, 250 rhizobial strains were isolated from legumes belonging to different geographical locations of Chhattisgarh, India. Genetic diversity of the nitrogenfixing bacterial community was analyzed using the nifH gene-specific primer. The polymorphism was found among the nitrogen-fixing population of different sources and origin but not in same source of rhizobia. Further, the symbiotic plasmid DNA was characterized on the basis of size and copy number of plasmids. The plasmid number varying from one to three in different rhizobial isolates had a size greater than 23 kb, while in some rhizobial isolates plasmids were absent. In addition, to examine the role of ascorbate in respiratory protection, the clear black spot margin of ascorbate was observed in the endodermis region of the nodule whereas scarcely dispersed in the infected region. Therefore, our findings demonstrated that knowing the rhizobial nifH gene diversity along with copy number of the plasmid is important for strain identification, deciding its fertility, productivity standards, and potential of biological nitrogen fixation across the geographical region.     

Estimation of potassium concentration in oil palm (Elaeis guineensis Jacq.) leaf tissue by simple and inexpensive water extraction method

Estimation of potassium (K) concentration in oil palm leaf tissue is routinely carried out in oil palm plantations to manage fertilizer application for getting higher fresh fruit bunch (FFB) production. Since K in plant tissue is not bound to organic complexes and it is extractable by water, this study was carried out to extract K from oil palm leaf tissue by water extraction method. The results were compared with other established methods like 1 normal (N) ammonium acetate (NH₄OAc) extraction, 0.5 N hydrochloric acid (HCl) extraction, and diacid digestion. The proposed water extraction method consists of shaking of 0.5 g finely ground oil palm leaf tissue with distilled water at 1:60 ratio [sample-to-water weight (w)/volume (v)] for a period of 20 min in a reciprocating shaker, filtration of the content, and measurement of K concentration in filtrate by flame photometer. The results of analysis of 30 oil palm leaf samples collected from various production systems under different soil types and management practices for K concentration revealed the close agreement of water extraction method with other established methods. The mean value of K extracted by water extraction method was within 1–10% of the K extracted by other established methods. Water-extractable K was significantly correlated with K extracted by other methods and it could be predicted by other methods. The values of standard error and coefficient of variation for K extracted by different methods were very low, which indicated that the water extraction method was comparable with other established methods.     

Soil Nutrient Status and Leaf Nutrient Norms in Oil Palm (Elaeis Guineensis Jacq.) Plantations Grown in the West Coastal Area of India

Oil palm (Elaeis guineensis Jacq.) is a heavy feeder of nutrients and requires balanced and adequate supply of nutrients for optimum growth and yield. Information regarding soil nutrient status and leaf nutrient concentration is very much required for proper fertilizer application. Therefore, a survey was conducted for assessment of soil nutrient status and leaf nutrient concentration in 64 oil palm plantations in the state of Goa lying in the west coastal region of India. Soil pH, electrical conductivity (EC), organic carbon (OC), available potassium (K) (ammonium acetate-extractable K) (NH₄OAc-K), available phosphorus (P) (Bray’s-P), exchangeable calcium (Ca) (Exch. Ca) and magnesium (Mg) (Exch. Mg), available sulphur (S) (calcium chloride-extractable S) (CaCl₂-S), and hot water soluble boron (B) (HWB) in surface (0–20 cm depth) soil layers ranged from 4.25 to 6.77, 0.05 to 1.06 dS m^–1, 5.07 to 48.4 g kg^–1, 58.1 to 1167 mg kg^–1, 1.80 to 415 mg kg^–1, 200 to 2997 mg kg^–1, 36.0 to 744 mg kg^–1, 3.00 to 87.7 mg kg^–1 and 0.09 to 2.10 mg kg^–1, respectively. Diagnosis and Recommendation Integrated System (DRIS) norms were established for different nutrient expressions and were used to compute DRIS indices. As per DRIS indices, the order of requirement of nutrients in the region was found to be P > Mg > K > nitrogen (N) > B. Optimum leaf nutrient ranges as per DRIS norms varied from 1.64 to 2.79%, 0.36 to 0.52%, 0.37 to 0.75%, 0.89 to 1.97%, 0.35 to 0.63%, 0.89 to 1.50%, 3.10 to 13.9 mg kg^?1, 7.50 to 32.2 mg kg^?1, 35.0 to 91.1 mg kg^?1, 206 to 948 mg kg^?1, and 895 to 2075 mg kg^?1 for N, P, K, Ca, Mg, S, B, copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) respectively. On the basis of DRIS-derived sufficiency ranges, 14, 5, 11, 6, 6, 6, 8, 2, 3, 6, and 16% of leaf samples had less than optimum concentrations of N, P, K, Ca, Mg, S, B, Cu, Zn, Mn, and Fe respectively. The optimum ranges developed can be used as a guide for routine diagnostic and advisory purpose for balanced utilization of fertilizers.     

Lipid profile of rats fed blends of rice bran oil in combination with sunflower and safflower oil

This study was undertaken to assess the effect of blended oils, i.e., polyunsaturated fatty acid (PUFA) rich vegetable oils like safflower oil (SFO) and sunflower oil (SNO) with the unconventional and hypocholesterolemic rice bran oil (RBO) on the serum lipid profile of rats. Rats fed RBO + SNO/SFO at 70:30 ratio for a period of 28 days showed significantly (p < 0.05) lower levels of total cholesterol (TC), triglycerides (TG) and low density lipoprotein (LDL) cholesterol and increased high density lipoprotein (HDL) cholesterol in animals fed a high cholesterol diet (HCD) and cholesterol free diet (CFD). Liver total cholesterol (TC) and triglycerides (TG) were also reduced. Fecal excretion of neutral sterols and bile acids was increased with use of RBO blends. RBO, which is rich in tocopherols and tocotrienols, may improve the oxidative stability of the blends. Tocotrienols are known to inhibit 3-hydroxy, 3-methyl, glutaryl CoA (HMG-COA) reductase (rate limiting enzyme in cholesterol biosynthesis), resulting in hypocholesterolemia. In addition to improving the lipid profile by lowering TC, TG and LDL-C and increasing HDL-C, blending of RBO with other oils can result in an economic advantage of lower prices.     

Red palm oil as a source of β-carotene for combating vitamin A deficiency

Twenty four school children of 7–9 years of age were divided into two groups of six boys and six girls each. One group was given a daily supplement of Suji halwa, a sweet snack made with semolina and red palm oil, supplying 2400 µg of -carotene and the second group was the control group which was given 600 µg of oral vitamin A palmitate, for 60 days. Vitamin A status before and after supplementation was assessed by the Modified Relative Dose Response Assay (MRDR). Results indicated that serum vitamin A levels increased from the basal level of 0.86±0.13 µmol/l to 1.89±0.23 µmol/l in the Red Palmoil (RPO) group and from 0.74±0.09 to 1.94±0.21 µmol/l in the control vitamin A group. Dehydroretinol/Retinol (DR/R) ratio decreased from 0.073±0.025 to 0.023±0.004 in the RPO group and from 0.090±0.023 to 0.023±0.004 in the vitamin A group, indicating liver saturation with vitamin A after feeding RPO snacks, comparable to synthetic vitamin A. This study indicates that RPO is an efficient source of -carotene which is found to be bioavailable in all the subjects tested, hence it can be used for supplementary feeding programmes to combat vitamin A deficiency in target population.     

Soil fertility and yield-limiting nutrients in oil palm plantations of north-eastern state Mizoram of India

A survey was conducted for assessment of soil fertility status, leaf nutrient concentration and finding yield-limiting nutrients of oil palm (Elaeis guineensis Jacq.) plantations in Mizoram state situated in the northeastern part of India. Soil pH, electrical conductivity (EC), organic carbon (OC), available potassium (K), available phosphorus (P) (Bray's-P), exchangeable calcium (Ca) (Exch. Ca) and magnesium (Mg) (Exch. Mg), available sulfur (S) (CaCl₂-S), and hot-water-soluble boron (B) (HWB) content in surface (0–20 cm depth) and subsurface (20–40 cm depth) soil layers varied widely. Diagnosis and Recommendation Integrated System (DRIS) norms were established for different nutrient expressions, and DRIS indices were computed. As per DRIS indices, the order of requirement of nutrients was found to be B > K > Mg > P > nitrogen (N). Optimum leaf nutrient ranges as per DRIS norms varied from 1.91% to 2.95%, 0.46% to 0.65%, 0.63% to 1.00%, 0.48% to 0.88%, and 9.41 to 31.0 mg kg^?1 for N, P, K, Mg, and B, respectively. On the basis of DRIS-derived optimum ranges, 32%, 9%, 27%, 12%, and 12% leaf samples had less than optimum concentration of N, P, K, Mg, and B, respectively. The optimum ranges developed could be used as a guide for routine diagnostic and advisory purpose for efficient fertilizer application.     

Isolation and characterization of lipopolysaccharides from different rhizobial isolates

Formation of nodules on roots or in stems (in some cases) of leguminous plants is the unique ability of gram-negative bacteria, Rhizobia, which converts atmospheric nitrogen into usable forms by the host plant. Lipopolysaccharide (LPS) is the outer membrane component of the gram-negative bacteria, known to be an essential factor in host recognition, specificity, and initial infection processes. In the present study, we extracted lipopolysaccharides from different rhizobial isolates by a modified phenol-water method and partially characterized by polyacrylamide gel electrophoresis with silver staining. The results showed two separate banding regions, LPS-I and LPS-II. The high molecular weight and electrophoretic mobility of LPS-I region resembles that of lysozyme, used as a standard marker. The LPS-II region has a low molecular weight and electrophoretic mobility greater than that of lysozyme. The LPS-II region was due to incomplete LPS, which either lacks the entire O-antigen repeating unit or contains only one or two repeating units. The banding patterns of LPS vary among the different rhizobial isolates. Results revealed that the type of LPS structure and banding regions greatly facilitate the further characterization of the LPS modifications required for symbiosis.