A Flow Cytometry-Based Assessment of the Genomic Size and Ploidy Level of Wild <i>Musa</i> Species in India

The genome size variation is an important attribute in evolutionary and species characterization. <i>Musa</i> L. is regarded as one of the taxonomically complicated genera within the order Zingiberales, with more than 75 species from wild seeded to seedless cultivars that may be diploid, triploid or tetraploid. The knowledge of total nuclear DNA content in terms of genome size and ploidy level in wild species of <i>Musa</i> is absolutely important in evolutionary and genomic studies. Methods: In this paper, chromosome spreading was performed via protoplast isolation and a fast air-dry dropping method and flow cytometry were used with <i>Raphanus sativus</i> L. (Brassicaceae) as a standard for ploidy and genome size estimation. Results: The results showed that genome size (2C) varied amongst <i>Musa</i> species, based on the ratio of G1 peak positions. The lowest genome size (2C) was found in <i>M. balbisiana</i> var. <i>andamanica</i> (1.051 ± 0.060 pg) and the highest genome size (2C) was recorded for <i>Musa</i> ABB.cv. Meitei-hei (1.812 ± 0.108 pg) for the section <i>Eumusa</i>. Among the species belonging to the section <i>Rhodochlamys</i>, <i>M. rosae</i> had the lowest 2C content of 1.194 ± 0.033 pg whereas the highest nuclear DNA content (2C) was observed in <i>M. velutina</i> (1.488 ± 0.203 pg). Cytogenetic analysis revealed that the chromosome number of 14 wild <i>Musa</i> species was 2n = 22, while 1 species—<i>Ensete glaucum</i>—showed a chromosome number of 2n = 18 (diploid), and for 3 species, the chromosome number was 2n = 33 (triploids). An association study based on the Pearson correlation coefficient showed 2C nuclear DNA content was significant and positively correlated with ploidy level (R = 0.9) and chromosome number (R = 0.84). Conclusions: The present study provides reliable information on the genome size and ploidy level of wild <i>Musa</i> species from the Indian region through flow cytometric analysis, which could be further utilized in taxonomic and crop improvement programs. For the first time, the nuclear DNA content of eight wild diploid and three triploid Indian species were estimated and reported. Genome size could be an effective indicator in identification of species and evolutionary studies in <i>Musa</i> with varying ploidy levels and morphological similarities.