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Phylogenetic Relationships of Algal Symbionts of Azolla and Free-Living Cyanobacterial Cultures Based on DNA Amplification

Azolla is a free floating water fern which fixes atmospheric nitrogen in association with nitrogen-fixing cyanobacterium Anabaena azollae. Random amplified polymorphic DNA technique was used to generate fingerprinting in symbiotic Anabaena azollae isolates viz., A. azollae-VBK-SK-AM, A. azollae-VBK-SK-AF, A. azollae-VBK-SK-TNAU and A. azollae -VBK-SK-RP as well as free-living cyanobacterial cultures viz., Anabaena variabilis, Nostoc muscorum (DOH), Westiellopsis sp. (Kew-SK) and Oscillatoria sp. A total of 15 random primers were used and the bands were scored as present or absent for each cyanobacterial cultures. The variation among cyanobacterial cultures was quantified using Nei's genetic distances. A dendrogram summarizing phenetic relationship among the cyanobacterial cultures was generated using the unweighted pair-group method with arithmetic mean. The statistical analysis was performed using “RAPDistance” 1.04, a computer program developed by John Armstrong (Research School of Biological Sciences, Institute of Advanced Studies, A.N.U., Australia). Three distinct groups were identified: group 1 contains four symbiotic A. azollae isolates, group 2 contains the free-living cyanobacterial cultures viz., A. variabilis, Nostoc muscorum (DOH) and Oscillatoria sp. whereas, Westiellopsis sp. (Kew-SK) was placed in the third group. The analysis demonstrated that the major cyanobacterial symbiont Anabaena azollae can be easily distinguished from the free-living cyanobacterial cultures.

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Konde, V., Kannaiyan, S. Phylogenetic Relationships of Algal Symbionts of Azolla and Free-Living Cyanobacterial Cultures Based on DNA Amplification. Nat Biotechnol 17, 45 (1999).

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