Vol.:(0123456789) 1 3 Planta https://doi.org/10.1007/s00425-019-03093-7 ORIGINAL ARTICLE Cyanobiont diversity in six Azolla spp. and relation to Azolla‑nutrient profling Upendra Kumar 1  · Amaresh K. Nayak 1  · Periasamy Panneerselvam 1  · Anjani Kumar 1  · Sangita Mohanty 1  · Mohammad Shahid 1  · Archana Sahoo 1  · Megha Kaviraj 1  · Himani Priya 1  · Nitiprasad N. Jambhulkar 1  · Pradeep K. Dash 1  · S. D. Mohapatra 1  · Prafulla K. Nayak 1 Received: 21 November 2018 / Accepted: 12 January 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Main conclusion Illumina-Miseq ® -based cyanobiont diversity and biomass were analyzed in six Azolla spp. Results revealed that 93–98% of total operational taxonomic units (OTUs) belong to Nostacaceae followed by Cylindrosper- mopsis with about 1–6% OTUs. The taxonomy of Azolla-cyanobiont is a long-term debate within the scientifc community. Morphological and biochemical- based reports indicated the presence of Anabaena, Nostoc and/or Trichormus azollae as abundant Azolla-cyanobionts, how- ever, molecular data did not support the abundance of Anabaena and/or Nostoc. To understand furthermore, the cyanobiont diversity in six species of Azolla (A. microphylla, A. mexicana, A. filiculoides, A. caroliniana, A. pinnata and A. rubra) was analyzed based on 16S rRNA Illumina-MiSeq sequencing. Additionally, biomass and nutrient profling of Azolla spp. were analyzed and correlated with cyanobiont diversity. Illumina-MiSeq data revealed that 99.6–99.9% of total operational taxonomic units (OTUs) belonged to Nostocophycideae (class), Nostocales (order) and Nostacaceae (family). At genus level, the unassigned afliation (93.4–97.9%) under Nostacaceae family was abundant followed by Cylindrospermopsis OTUs (1.1–6.0%). Interestingly, A. pinnata harboured maximum Cylindrospermopsis OTUs and also recorded higher biomass (40.67 g m −2  day −1 ), whereas crude protein (25.9%) and antioxidants (76.9%) were recorded to be higher in A. microphylla. Biplot analysis revealed that A. pinnata and its cyanobiont abundance were positively correlated with neutral and acid detergent fbers. Overall, the present fndings deepened the understanding about cyanobiont in Azolla and its relations with Azolla nutrient profling. Keywords Illumina-MiSeq ®  · Cyanobiont · Azolla · Taxonomy · Nutrient profling · Biomass Introduction Azolla is an aquatic fern that grows on the surface of fresh water ponds, lakes or streams which has been named by Lamarck in 1783 (Sood et al. 2008). On the basis of mor- phological and reproductive features, it has seven distinct species and these are grouped into two sections, namely Eua- zolla and Rhizosperma. Euazolla includes fve species of Azolla such as A. caroliniana, A. filiculoides, A. mexicana, A. microphylla and A. rubra (Lumpkin and Plucknett 1980), whereas the section Rhizosperma includes A. pinnata and A. nilotica (Plazinski et al. 1988). The amazing feature of Azolla is its symbiotic association with prokaryotic cyano- bacterium which confers high rates of nitrogen fxation and biomass production, hence, Azolla is used as efective green manure and biofertilizer for fooded crops particularly rice in many countries (Bhuvaneshwari and Singh 2015). Two types of endosymbionts were reported in Azolla, one is a nitrogen-fxing flamentous cyanobacterium which was frst reported by Strasburger as Nostoc in 1873, and then it was renamed as Anabaena azollae in 1884 (Adams Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-019-03093-7) contains supplementary material, which is available to authorized users. * Upendra Kumar upendra.kumar1@icar.gov.in; ukumarmb@gmail.com 1 ICAR-National Rice Research Institute, Cuttack, Odisha 753006, India