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.Keywords: biofertilisers, biofilms, cyanobacteria, maize, nutrient sequestratio

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

<div><p>The influence of biofilmed formulations composed of <i>Trichoderma viride</i> and <i>Anabaena torulosa</i> as matrices was investigated in <i>Macrophomina phaseolina</i> (Tassi) Goid.-infected cotton crop, in terms of plant growth and biocontrol parameters. <i>Trichoderma</i> based biofilms were developed with <i>Azotobacter chroococcum, Pseudomonas fluorescens</i> and <i>Bacillus subtilis,</i> while <i>A. torulosa</i> biofilms were prepared using <i>B. subtilis</i> and <i>T. viride</i> 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 <i>T. viride</i>–<i>B. subtilis</i> biofilm. An increase of 4–7% in polyphenol oxidase enzyme activity was recorded in all biofilm-treated samples, particularly those in which <i>B. subtilis</i> was present. The highest value of 1360.22 µg microbial biomass carbon g⁻¹ soil was recorded in <i>Anabaena–B. subtilis</i> 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.</p></div

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

<div><p></p><p>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 (<i>Anabaena</i>–<i>Azotobacter</i> 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 (<i>Anabaena</i>–<i>Azotobacter</i> biofilm) and A1 (<i>Anabaena</i> sp.–<i>Providencia</i> 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 (<i>Anabaena</i>–<i>Trichoderma</i>-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.</p></div