Alternative Oxidase Gene (Aox I): A Good DNA Barcoding Candidate for the Genus Fusarium

Resumen

DNA barcoding is a tool for taxonomy analysis that uses a short standard genomic sequence present in all the taxa of interest, which has enough sequence variation to discriminate among species. Members of the genus Fusarium are recognized as saprophytes and important plant and human pathogens, and their taxonomic identification commonly relies on macro and microscopical characteristics and molecular methods. However, identification can be difficult due to the lack of some structures in culture or poor polymorphism in ribosomal DNA sequences. Barcoding could provide an easy and reliable method to overcome these problems. This study is a preliminary study to evaluate sequences of Cox (mitochondrial cytochrome oxidase subunit I) and Aox (alternative oxidase) as potential DNA barcodes for identification of Fusarium species. DNA was extracted from 12 Fusarium isolates previously identified by traditional methods into different complexes: F. solani, F. oxysporum and Gibbellera fujikuroi. For PCR amplification of Cox 1 gene, primers designed in a previous study were used and amplicons of approximately 600 pb were observed in all the isolates. For the amplification of Aox, primers were designed by our group showing amplification of a region of 800 bp approximately in all Fusarium species. The sequences were clustered using phylogenetic trees, additionally, intra-and interspecific divergence were estimated with the K2P model. These results showed that the Aox sequence clustered the isolates into the appropriate Fusarium species complex, according to previous morphological characterization, indicating its potential to differentiate Fusarium isolates to the species level. Similarity analysis of Cox1 sequences showed insufficient variation to discriminate among isolates. In conclusion, the 800 bp sequence of AOX is a candidate to become a DNA barcode sequence, but more species and isolates are needed to further test its discriminating ability.