Prospecting the promise of cyanobacterial formulations developed using soil-less substrates as carriers

Abstract Cyanobacteria are widely used as biofertilizers and their effectiveness is influenced by the type of carrier, which in turn, dictates the viability of the inocula being introduced for improving plant growth. Soil-less substrates were explored as carriers in the present investigation, the potential of perlite (P), cocopeat (C) and vermiculite (V), individually and in combinations (1:1) such as - perlite: cocopeat, perlite: vermiculite, cocopeat: vermiculite, and perlite: cocopeat: vermiculite (1:1:1.) was screened. Four agriculturally beneficial cyanobacterial cultures/biofilms - Calothrix elenkinii, Anabaena laxa, Anabaena torulosa – T. viride (An-Tr) and A. torulosa – Bacillus sp. (An-Bs) were characterised and shelf-life evaluated after augmenting them to such substrates. Time course analyses after 2, 10 and 20 weeks illustrated that chlorophyll, as an index of photosynthetic biomass and population counts of the bacterial/fungal partner of biofilms enhanced significantly. For their use as disease suppressive options, fungicidal activity against phytopathogenic fungi was tested and found to be enhanced with the period of incubation. P: C and C:V were identified as most promising, and augmentation with cyanobacteria/biofilms showed significant cyanobacterial colonisation in the substrate after 20 weeks, illustrating their extended shelf-life. PCR amplification using 16S cyanobacterial, bacterial and fungal ITS directed primers confirmed the utility of these substrates. Seed germination test with maize, radish and wheat seeds showed marginal increases as a result of augmentation, with no phytotoxicity, and these novel mixes need to be tested in pot and field experiments as inoculants.