A checklist of blue-green algae (Cyanobacteria) from Punjab, India

: A checklist of Cyanobacteria (Blue-green algae) has been made by reviewing available literature in order to contribute to the knowledge of biodiversity of algae in the Punjab state of India. The list records 317 taxa of the phylum Cyanobacteria distributed among 74 genera, 32 families, and six orders. The order Oscillatoriales has 115 taxa, followed by Nostocales (84), Synechococcales (60), Chroococcales (49), Spirulinales (8), and Pleurocapsales (1). The family Nostocaceae has the maximum number of genera followed by Microcoleaceae, Chroococcaceae, Oscillatoriaceae and other reported families. The genera with the highest number of species were Phormidium (39 species), Lyngbya (15 species), Oscillatoria (14 species), and Leptolyngbya & Scytonema (13 species each). The checklist revealed a high degree of species richness within phylum Cyanobacteria found in Punjab. This checklist can provide a baseline for future floristic studies with taxonomically updated/accepted name of genera/species of cyanobacteria.


INTRODUCTION
Cyanobacteria, also known as Blue-green algae, are oxygenic photosynthetic prokaryotes belonging to the class Cyanophyceae. It has been estimated that these organisms originated nearly 3.5-3.8 billion years ago at the beginning of Archean era (Schopf 2002;Blank & Sanchez-Baracaldo 2010;Sleep 2010). Cyanobacteria occur in diverse range of aquatic and terrestrial habitats including extreme environments (Whitton & Potts 2000;Singh et al. , 2018Kimambo et al. 2019). They show high degree of phenotypic variation when compared to other prokaryotic organisms (Dvořák et al. 2017). Traditionally these organisms have been identified and categorized mainly using morphological features such as dimension, shape of vegetative and perennation stage, colour & characteristics of sheath, branching pattern, and cell contents (Komárek & Anagnostidis 1998, 2005Komárek 2013). Presently, the advancement and use of modern taxonomic tools including ultrastructural studies, 16S rRNA gene, 16S-23S rRNA ITS region and cpcB-cpcA IGS region of phycocyanin locus has lead to the changes in taxonomic position of various cyanobacterial genera/ species (Komárek 2014). The ability of cyanobacteria to release exopolysaccharides and fix atmospheric nitrogen is pertinent in maintaining a healthy condition of the soil; addidtionally, this ability can further assist with the reclamation of barren land (Singh et al. 2016). In recent years, cyanobacterial research has gained greater academic interest as many species in this phylum have been identified to be a potential source of various valueadded products such as biofertilizers, biofuels, and bioactive compounds. Cyanobacteria is also an attractive laboratory model that is used for genetic studies to understand their adaptation to extreme conditions and climatic changes. (Abed et al. 2008;Al-Haj 2016;Singh et al. 2017;Kumar et al. 2019).
Cyanobacteria have been reported from various habitats in Punjab including wetlands, paddy fields and polluted water etc. (Vasishta 1960a(Vasishta , 1961(Vasishta , 1962a(Vasishta ,b, 1963Pandhol 1974;Grover & Pandhol 1975;Mehta 1975;Sarma et al. 1979;Dhingra 2006;Singh et al. 2009;Khattar et al. 2015). Despite an increase in research effort, knowledge regarding the diversity and distribution of cyanobacteria in Punjab is still inconsistent. Thus there is need for an updated species checklist in order to contribute to the current knowledge of cyanobacterial diversity of the state. Although, in Gupta (2012) published a checklist of cyanobacteria from India in which 218 cyanobacterial taxa were reported from Punjab, the present study adds 99 taxa to this list, hence increasing the total to 317 taxa. Since cyanobacteria are an important component of the aquatic ecosystem, cyanobacterial wealth of the state should be known so that these can be collected and cultured for future studies.
The objective of this work was to revise and organize all available existi ng taxonomic data for cyanobacteria of recent taxonomic revisions in the state of Punjab. The checklist could serve as a baseline for future diversity, limnological, environmental impact assessment, bio-geographic distribution and speciation studies. Creation of a checklist is the most basic taxonomic work on a group of organisms arranged in systematic or alphabetical order. The checklist prepared during present work is done in a systematic order by reviewing the available literature up to September 2020. This is the first complete checklist of cyanobacteria from Punjab covering all currently accepted species names and their synonyms.

MATERIALS AND METHODS
This checklist has been prepared by consulting available literature including research papers and dissertations (PhD/ M.Phil/ MSc.). Data were compiled by reviewing diversity, taxonomy and ecological studies containing lists of cyanobacteria identified up to species level. Geographically, Punjab is situated in the north of the country between 29.30-32.32 °N and 73.55-76.50 °E ( Figure 1). The climate of Punjab is continental, semiarid to sub-humid, it experiences both extreme summer and winter with annual rainfall of 58-96 cm (Gosal 2004;Krishan et al. 2015). The texture of soil in Punjab varies from coarse to fine sand, silt, and loam (Dhingra 2006). Cyanobacterial species recorded in this checklist were identified by various workers from the year 1936 to 2020. In this checklist species were arranged taxonomically by following the classification system recommended by Komárek (2014). Additionally, the taxonomic position, authorities and the currently accepted name was verified from AlgaeBase website (Guiry & Guiry 2020).

RESULTS AND DISCUSSION
This compiled checklist revealed that cyanobacterial diversity within Punjab is represented by 317 taxa (297 species, 13 varieties, and 7 forms) belonging to 74 genera and five orders (i.e., Chroococcales,
The taxonomic identity of 87 cyanobacterial taxa previously reported from Punjab on their morphology has been revised with the help of modern taxonomic tools (marked with '*' in Table 1). Current accepted names of such taxa were updated following Algaebase. Taxonomic revision is continuous leading to the revision of taxonomic status as well as the nomenclature of the organism. Application of modern ecological, ultra-structural and molecular methods, aided by the cultivation of numerous cyanobacterial morphotypes, has substantially changed our knowledge of these organisms (Komárek 2006). Modern taxonomic tools have also enabled major advances in cyanobacterial taxonomy and aided with the criteria used for their phylogenetic classification (Komárek 2006(Komárek , 2014. Cyanobacteria recorded from Punjab inhabit varied habitats from planktonic to terrestrial and epilithic to epiphytic. Observations made from the present checklist note that the number of cyanobacterial species growing on terrestrial habitats (110) were greater than planktonic (84), epilithic (26), and epiphytic (15) ( Table 1). However, 78 cyanobacterial species were reported from more than one habitat (Table 1, Figure 3). They colonize large portions of the available terrestrial habitats due to its ability of 'anhydrobiosis' (Billi & Potts 2002;Alpert 2005). Moreover, they have a wide distribution range due to their unimaginable adaptive capacities (Gaysina 2019).
In conclusion, as a first complete and updated checklist of cyanobacteria from Punjab this will provide a baseline data for future floristic study. The explored and poorly explored regions of Punjab in terms of number of cyanobacterial taxa are highlighted in Figure 1. We can also assume that future studies of cyanobacterial diversity from poorly explored regions will increase the number of species by exploring more unexplored habitats of Punjab. publication, National University of Ireland, Galway. https://www.
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