Karyotype analysis of Alocasia cucullata (Lour.) Schott using fluorochrome banding and fluorescence in situ hybridization with rDNA probes

Alocasia cucullata (Lour.) Schott is an Araceae plant of ornamental and medicinal use grown in many parts of Asia. The cytogenetics of this species have not yet been reported, except for the chromosome number. In this study, sequential combined propidium iodide (PI) and 4', 6-diamidino-2-phenylindole (DAPI) (CPD) staining and dual-color fluorescence in situ hybridization (FISH) with 5S and 45S rDNA probes were employed for the chromosome analysis of this species. A. cucullata has a diploid chromosome number of 2n = 28, and a karyotype length of 108.53 +/- 11.29 mu m with the chromosome size ranging from 9.19 to 6.19 mu m. CPD staining revealed two pairs of red CPD bands at the terminals of the short arms of two submetacentric chromosome pairs and a pair of DAPI(+) bands in the interstitial regions of the long arms of a metacentric pair. FISH of the rDNA probes revealed two pairs of 45S rDNA loci corresponding to the CPD bands, and a single 5S rDNA locus located in the interstitial regions of the short arms of the DAPI-banded pair. The chromosome measurements, fluorochrome bands and rDNA FISH signals were used to identify the chromosomes, and the molecular cytogenetic karyotype of this species were established. The karyotype was formulated as 2n = 4x = 28 = 20m + 8sm, and the six asymmetry indices, CI, A1, A2, As K%, AI and the Stebbins' type were 40.40 +/- 6.65, 0.30, 0.13, 59.08, 2.09 and 2A, respectively.