Genetic diversity of nitrate reducing bacteria in marine and brackish water nitrifying bacterial consortia generated for activating nitrifying bioreactors in recirculating aquaculture systems

Nitrate reducing potency of 88 bacterial isolates segregated from marine and brackish water nitrifying bacterial consortia (NBC), generated for activation of nitrifying bioreactors, was confirmed by determining the nitrate reducing capability under aerobic conditions as maintained in nitrifying bioreactors. All the isolates had the potential to be used as bio‐augmentors for activating nitrate dissimilation in recirculating aquaculture system. The existence of nitrate reducers with nitrifiers in NBC and in the reactor configuration negates the requirement of integrating anoxic denitrifying system for effective removal of NO₃^?‐N. Phylogenetic analyses of representative isolates from each cluster of the dendrograms generated based on phenotypic characterization and amplified ribosomal DNA restriction analysis revealed profound diversity of nitrate reducing bacterial flora in the NBC. They were composed of Streptomyces enissocaesilis, Marinobacter sp., Pseudomonas sp., Microbacterium oxydans, Pelagibacterium halotolerans and Alcanivorax dieselolei from marine NBC and Streptomyces tendae, Nesterenkonia sp., Bacillus cereus, Microbacterium oxydans and Brevibacterium sp. from brackish water NBC. The diversity indices of the consortia were calculated using Mega 5.0, primer 7 and VITCOMIC softwares. Marine NBC exhibited higher Shannon wiener diversity and mean population diversity than brackish water NBC. The study delineated higher species richness and diversity in marine NBC than in its brackish water counterpart, a possible reflection of the higher biodiversity of marine systems, and hence, the former is more promising to be used as start‐up cultures for the activation of nitrifying bioreactors after appropriate acclimatization to the desired salinity.     

Transmission of a mycoplasma-like organism from cocos nucifera with root (wilt) disease to Catharanthus roseus by Cassytha filiformis

A mycoplasma-like organism (MLO) was successfully transmitted through dodder laurel (Cassytha filiformis) from root (wilt) diseased coconut to periwinkle (Catharanthus roseus) plants. Symptoms caused by the organism in periwinkle were chlorotic spots in the interveinal areas and at vein endings of fully opened leaves, later coalescing into yellow patches, and premature leaf abscission. Light and electron-microscopic examination revealed the presence of MLOs in diseased coconut palms, dodder laurels and periwinkles.Samenvatting Door de als warkruid groeiende lauraceeCassytha filiformis werd van kokosnootpalm (Cocos nucifera), aangetast door root(wilt), een mycoplasma-achtig organisme (MLO) overgebracht naar de toetsplantCatharanthus roseus. Hierop werden op de bladeren tussennervige, later ineenvloeiende vlekken en vroegtijdige bladval waargenomen. Uit onderzoek met de lichtmicroscoop en de elektronenmicroscoop kon de aanwezigheid van MLO's inCocos nucifera, Cassytha filiformis enCatharanthus roseus worden vastgesteld.CPCRI contribution No 622     

Effect of Zn application on its uptake,distribution and concentration of Fe and Cu in finger millet [Eleusine coracana (L.) Gaertn.]

Zinc (Zn) malnutrition can be alleviated by increasing the dietary Zn intake through Zn biofortification of edible crops. Agronomic and genetic biofortification has been suggested as better option to increase the dietary Zn. In this study, we show considerable genetic variability for seed Zn concentration in six leading finger millet genotypes. External application of Zn resulted in improved Zn concentration in different plant parts; in particular there was significant increase in seed Zn concentration in all genotypes. Though genotypes GPU28 and INDAF5 showed differences in root and shoot Zn at vegetative stage but at reproductive stage there was no significant difference. Apart from that, Zn application increased the seed iron (Fe) concentration with no or minimal effect on copper (Cu) concentration.     

Differential response of rice seedlings to salt stress in relation to antioxidant enzyme activity and membrane stability index

Three rice genotypes, IR 74802, IR 73104 and IR 72593, along with FL 478 and IR 29 as resistant and susceptible controls, respectively, were subjected to 21 days' salinity stress at the seedling stage in modified yoshida solution with two salt levels (60 and 120 mM NaCl). The results indicated that there was a profound increase in proline and ascorbic acid levels, and in the activity of nitrate reductase and antioxidant enzymes, i.e. catalase, peroxidase and ascorbate peroxidase, as well as malondialdhyde and membrane stability index, which were associated with salt tolerance. Salt stress had a significant and drastic effect on all parameters when the salinity level increased to 120 mM NaCl. The increased enzyme activity was directly related to an increased membrane stability index, as in IR 72593, which is identified as the most tolerant among the genotypes tested. It is clearly confirmed that predicting tolerance at the early seedling stage is the best way to assess the salinity tolerance level by utilizing physiological parameters, especially antioxidant enzyme activities which are found to be closely associated with salinity tolerance. Physiological adaptation of the plant to NaCl salt stress resulted in enhanced activity of stress-related enzymes and low sodium uptake in tolerant genotypes.     

Effect of sewage irrigation on nitrate accumulation and nitrate reductase activity in leafy vegetables

The effect of sewage water irrigation along with the N-fertilizers on NO3 accumulation and on the in vivo NR assay in three leafy vegetable crops were studied. It was found that the NO3 content in the leaves from the experimental sites were around two fold than the control and the NR enzyme activity was comparatively more in the control samples. The in vivo NRA with NaCl treatment increased at low level of NaCl where as with high level of NaCl, the enzyme activity decreased considerably. This is suggestive of the fact that NO3 accumulation may be due to antagonistic effect of chloride ions.     

Modeling Variability of Alfisols Fertility Parameters in Micro-Watersheds of Harve,Chamarajanagara District in Semi-Arid,India

Assessment of soil-fertility of a sub-watershed is pre-requisite for efficient rainfed agriculture. Soil survey was conducted in Harve sub-watershed (Kumachahalli-1,Kumachahalli-2,KG Hundi,Kengaki,Bettadapura,Sagade micro-watersheds) to assess soil homogeneity. Based on analysis of soil-fertility data, pH had lowest, while manganese (Kumachahalli-1), magnesium (Kumachahalli-2,KG Hundi,Sagade), zinc (Kengaki), copper (Bettadapura) had highest variation. Principal component (PC) analysis indicated that 5 PCs explained 66.96% (Sagade)–74.08% (Kumachahalli-2) variance. Comparison of P₁ and P₂ indicated zinc (Kengaki), copper (Bettadapura), nitrogen, carbon (Kumachahalli-1); while P₁ and P₃ indicated carbon (Sagade), magnesium, calcium (Kumachahalli-2); P₂ and P₃ indicated carbon (Kengaki) as important with loading >0.70. Comparison of variation with P₁ indicated pH (all locations), potassium (KG Hundi,Kengaki,Kumachahalli-2), electrical conductivity (Kumachahalli-2), carbon (Sagade); P₂ indicated carbon, nitrogen (Kumachahalli-1); P₃ indicated carbon (Kengaki), zinc (Sagade), calcium (Kumachahalli-2) as important. Kumachahalli-2 was superior with maximum soil homogeneity. The findings are useful for developing soil test-based fertilizer doses for crops under Alfisols.     

Antifungal fractions and compounds from uncrushed Green Leaves ofAzadirachta indica

Using the groundnut rust disease (causal agentPuccinia arachidis Speg.) as the bioassay system, two limonoids from the neem tree (Azadirachta indica A. Juss.) which evinced antifungal activity, were isolated through extraction, solvent fractionation and HPLC. A polar extract derived through solvent partitioning reduced the disease intensity considerably. The polar extract and the impure HPLC fractions were more effective than the pure compounds in reducing the pustule numbers and, consequently, the disease severity.     

An efficient micropropagation system for Celastrus paniculatus Willd.: a vulnerable medicinal plant

A micropropagation protocol was developed for Celastrus paniculatus, a vulnerable medicinal plant. Cultures were initiated from nodal explants collected from young shoots of a 12-year-old plant in MS basal medium. An average of five shoots were produced in MS medium supplemented with 1.5 mg l⁻¹ benzyl adenine (BA) and 0.1 mg l⁻¹ naphthalene acetic acid (NAA) after two subculture cycles with a 30-day interval. Continuous subculture in the same medium for three more cycles resulted in reduction of the number of multiple shoots (2 or 3 shoots), vitrification of the shoots, and callus formation. Vitrification of cultures could be overcome by the use of MS medium supplemented with lower concentrations of BA (0.05 mg l⁻¹) and NAA (0.01 mg l⁻¹). Among the various rooting trials, ex vitro rooting of shoots with simultaneous hardening was most efficient. The method standardized in the present study is simple, as it eliminated separate steps for in vitro rooting and hardening. Qualitative chemical similarity of the tissue culture regenerants with the mother plant was confirmed using high performance thin-layer chromatographic (HPTLC) profiling.