Ngangom Bidyarani

Evaluating the efficacy of cyanobacterial formulations and biofilmed inoculants for leguminous crops

Our investigation was aimed towards evaluating the agronomic potential of biofilmed preparations (developed using Anabaena/Trichoderma as matrices with different agriculturally useful bacteria/fungi as partners) and selected cyanobacterial strains (Anabaena laxa (T7) RP8/Calothrix sp.). The formulations were prepared using paddy straw compost:vermiculite (1:1) as carrier and tested as inoculants in mungbean and soybean. The effects of the formulations were evaluated in terms of microbiological, nutrient availability, and plant biometric parameters. The Trichoderma viride–Bradyrhizobium biofilm exhibited 20–45% enhancement in fresh/dry weight of plants over other microbial treatments, while the T. viride–Azotobacter biofilm exhibited highest dehydrogenase activity in the soil and nitrogen fixation. T7 RP8 recorded statistically at par yield values with the T. viride–Bradyrhizobium (T5) biofilm treatment in mungbean. In soybean, among all the treatments, the T5 biofilm recorded the highest fresh weight of plants and available N in soil at harvest. The Anabaena–T. viride biofilmed formulations proved to be the most promising for soybean, recording 12–25% enhanced yield and microbial activity (measured as dehydrogenase activity). This study highlights the promise of cyanobacterial inoculants and biofilmed biofertilizers as promising inputs for integrated nutrient management strategies in agriculture.

PROSPECTING CYANOBACTERIA-FORTIFIED COMPOSTS AS PLANT GROWTH PROMOTING AND BIOCONTROL AGENTS IN COTTON

The potential of cyanobacteria-based compost formulations was evaluated in cotton crop at two agro-ecological locations (Nagpur and Sirsa) as plant growth promoting (PGP) and biocontrol agents. Compost-based formulations fortified with Calothrix sp. or Anabaena sp. enhanced germination and fresh weight of plants, and microbiological activity by 10–15%, besides increased available nitrogen (by 20–50%) in soil at Nagpur. In the fungi-infected fields at Sirsa, Anabaena – T. viride biofilmed formulation performed the best, recording 11.1% lower plant mortality than commercial Trichoderma formulation. Scanning electron microscopy confirmed the colonisation of inoculated cyanobacteria/biofilms on roots. Significant correlation between mortality, increased activity of hydrolytic enzymes and fresh weight of plant roots were recorded. Calothrix sp. and Anabaena sp. proved promising as both PGP and biocontrol agents, while biofilmed formulations substantially reduced mortality of cotton plants in sick plots. This study illustrates the promise of cyanobacteria as viable inoculation option for integrated nutrient and pest management strategies of cotton.

Micronutrient enrichment mediated by plant-microbe interactions and rice cultivation practices

ABSTRACT A field experiment was conducted to evaluate the effect of different plant growth promoting microorganisms (PGPM) on micronutrient enrichment of rice crops grown under conventional (flooded) and SRI (System of Rice Intensification) practices. Significant differences were recorded among treatments and cultivation practices in terms of soil microbial activity reflected in enhanced nutrient uptake, enzyme activity, and yield. The Anabaena-based biofilm inoculants were particularly superior under both methods of cultivation, leading to 13–46% enhancement of iron and 15-41% enhancement of zinc in rice grains over uninoculated controls. SRI was found to be superior in terms of enhancing the concentration of zinc, copper, iron, and manganese (Zn, Cu, Fe and Mn), particularly in grains, and significant in increasing the activity of defense- and pathogenesis- related enzymes and yield parameters. This study illustrates the utility of cyanobacteria-based inoculants for both methods of rice cultivation and their significant interactions with the plant, leading to micronutrient enrichment of rice grains. Such formulations can complement the current biofortification strategies and help in combating the problems of malnutrition globally.

Cyanobacterial inoculation elicits plant defense response and enhanced Zn mobilization in maize hybrids

Abstract The present investigation evaluated the effect of inoculating different cyanobacterial formulations on a set of hybrids of maize, in terms of plant defense enzyme activity, soil health parameters, Zn concentration, and yields. Microbial inoculation showed significant effects on accumulation of Zn in flag leaf, with A4 (Anabaena–Azotobacter biofilm) recording the highest values. Analysis of variance (ANOVA) indicated that both the hybrids and cyanobacterial treatments brought about significant variation in terms of glomalin-related soil proteins and polysaccharides in soil and the activity of defense enzymes in roots and shoots of the plants. Cyanobacterial inoculants—A4 (Anabaena–Azotobacter biofilm) and A1 (Anabaena sp.–Providencia sp., CW1 + PW5) enhanced the activity of peroxidase, PAL and PPO in roots, which also showed a positive correlation with Zn concentration in the flag leaf. Grain yield ranged from 7.0 to 7.29 t/ha among the different inoculants. Comparative analyses of treatments showed that A3 (Anabaena–Trichoderma-biofilmed formulation) and hybrid B8 (Bio-9681) were superior in terms of parameters investigated. This represents the first report on the genotypic responses of maize hybrids to cyanobacteria-based inoculants. Future research should focus on dissecting the role of root exudates and cyanobacteria-mediated Zn mobilization pathway in maize.

Evaluating the promise of Trichoderma and Anabaena based biofilms as multifunctional agents in Macrophomina phaseolina-infected cotton crop

The influence of biofilmed formulations composed of Trichoderma viride and Anabaena torulosa as matrices was investigated in Macrophomina phaseolina (Tassi) Goid.-infected cotton crop, in terms of plant growth and biocontrol parameters. Trichoderma based biofilms were developed with Azotobacter chroococcum, Pseudomonas fluorescens and Bacillus subtilis, while A. torulosa biofilms were prepared using B. subtilis and T. viride as components. Scanning electron microscopy revealed significant colonisation of biofilms on the root surface, which could be correlated with lowest mortality of 5.67%, recorded using T. viride–B. subtilis biofilm. An increase of 4–7% in polyphenol oxidase enzyme activity was recorded in all biofilm-treated samples, particularly those in which B. subtilis was present. The highest value of 1360.22 µg microbial biomass carbon g−1 soil was recorded in Anabaena–B. subtilis biofilm treatment. Significantly higher values of plant and soil nutrient parameters in treatments in which biofilms were used vis-à-vis individual cultures reveal their promise. Such novel biofilmed biofertilizers with multiple useful traits can be beneficial options for effective nutrient and pest management of cotton crop.

Enhancement of plant growth and yields in Chickpea (Cicer arietinum L.) through novel cyanobacterial and biofilmed inoculants.

The use of Rhizobium inoculants in chickpea is well established; however, meagre efforts have been directed towards the use of other microbial supplements for improving nutrient uptake and yields. A set of novel cyanobacterial and biofilmed inoculants were evaluated in chickpea under field conditions. A significant two-fold enhancement in leghaemoglobin content of nodules and plant biomass was recorded with Anabaena laxa treatment. The inoculants - Anabaena laxa and Anabaena - Rhizobium biofilmed formulation proved to be the top-ranking treatments. Soil chlorophyll, nitrogen-fixation and available N possessed high positive direct effects on grain yield through positive - correlations and - high direct effects and also had high positive indirect effects through other component traits. The cumulative effect of improved plant growth and nutrient uptake exhibited a positive correlation with microbiological activity, especially nitrogen fixation, soil chlorophyll and soil available nitrogen. This may account for the significantly higher yield parameters in the A. laxa treatment, which recorded 50% higher grain yield (1724kgha(-1)) as compared to control (847kgha(-1)).

Deciphering the factors associated with the colonization of rice plants by cyanobacteria

Cyanobacteria‐rice plant interactions were analyzed using a hydroponics experiment. The activity of plant defense and pathogenesis‐related enzymes, scanning electron microscopy, growth, nitrogen fixation (measured as ARA), and DNA fingerprinting assays proved useful in illustrating the nature of associations of cyanobacteria with rice plants. Microscopic analyses revealed the presence of short filaments and coiled masses of filaments of cyanobacteria near the epidermis and cortex of roots and shoot tissues. Among the six cyanobacterial strains employed, Calothrix sp. (RPC1), Anabaena laxa (RPAN8), and Anabaena azollae (C16) were the best performing strains, in terms of colonization in roots and stem. These strains also enhanced nitrogen fixation and stimulated the activity of plant defense/cell wall‐degrading enzymes. A significantly high correlation was also recorded between the elicited plant enzymes, growth, and ARA. DNA fingerprinting using highly iterated palindromic sequences (HIP‐TG) further helped in proving the establishment of inoculated organisms in the roots/shoots of rice plants. This study illustrated that the colonization of cyanobacteria in the plant tissues is facilitated by increased elicitation of plant enzymes, leading to improved plant growth, nutrient mobilization, and enhanced plant fitness. Such strains can be promising candidates for developing “cyanobacteria colonized‐nitrogen‐fixing rice plants” in the future.

Prospecting cyanobacterial formulations as plant-growth-promoting agents for maize hybrids

Cyanobacteria represent environment-friendly inputs that can lead to savings of nitrogenous fertilisers, in addition to improving plant growth and soil fertility. The present investigation aimed to evaluate the potential of cyanobacteria inoculants as nutrient-management and plant-growth-promoting options for maize hybrids, which require high inputs of fertilisers. Four types of inoculants comprising consortia of cyanobacteria or cyanobacterium–bacterium and biofilmed preparations using Anabaena were evaluated for 11 maize hybrids. The microbial inoculants performed significantly better than the uninoculated control by bringing about 10–15% enhancement in Soil Plant Analysis Development (SPAD) value, plant height and available nitrogen (N) in the soil, which also led to a saving of 40 kg N ha−1. An additional enrichment of 40–50 kg N ha−1 in the soil was recorded in the treatments A1 (Anabaena–Providencia formulation) and A3 (Anabaena–Trichoderma biofilmed formulation). The cyanobacterial formulations A4 (Anabaena–Azotobacter biofilmed formulation) and A3 in conjunction with B10 (PMH-1), B8 (Bio-9681) and B9 (HM-8) proved to be superior associations. This is the first report on identification of promising cyanobacteria–maize genotype combinations as plant-growth-promoting and N-saving options. These results emphasise the significance of including cyanobacteria formulations in integrated nutrient management practices for this fertiliser-intensive crop.