Cytogenomic Analysis of Four Philippine Medicinal Plants Using Fluorescence In Situ Hybridization and Flow Cytometry

Chromosome numbers, karyotype, and genome size provide fundamental information for genome sequencing and breeding studies. Here, we analyzed the karyotype and genome size of four Philippine medicinal plants – namely Carica papaya (papaya), Citrus microcarpa (calamansi), Cymbopogon citratus (tanglad), and Moringa oleifera (malunggay). We performed a triple-color fluorescence in situ hybridization to detect the chromosomal distribution of the 5S and 35S rDNA and the Arabidopsis-type telomeric repeat. Citrus microcarpa (2n = 18, 2C = 0.95 pg) had one pair of 5S and 35S rDNA and a hemizygous 35S rDNA in the centromeric region of Chromosome 3. Carica papaya (2n = 18, 1.08 pg) had five pairs of 5S rDNA and one pair of 35S rDNA. Cymbopogon citratus (2n = 60, 3.79 pg) had four pairs of 5S rDNA and one pair of 35S rDNA. Moringa oleifera (2n = 28, 1.36 pg) had two pairs of 5S rDNA and five pairs of 35S rDNA. The telomeric repeat was detected in the chromosome termini of all chromosomes. Here, we present basic cytogenomics information on these four species, which can be useful for genomics, breeding, and evolutionary research. This approach can be replicated to gather cytogenomic information on endemic Philippine plants for genomics and conservation.