Fluorescent Staining and FISH of rDNA of Pitaya (Hylocereus spp.) Chromosomes

Abstract

Chromosome analysis of pitaya (Hylocereus spp.), a tropical fruit crop of the vine cactus, was conducted. All experiments were carried out using root tips derived from cutting plants as materials. Good chromosome samples all chromosomes relatively extended and well-spread without cytoplasm were prepared by the enzymatic maceration and air-drying method (EMA). The chromosome numbers of H. undatus, H. costaricensis, and H. megalanthus were 2n = 22, 22, and 44, respectively. In H. undatus and H. costaricensis, CMA-positive (+) bands were observed in telomeric positions of two chromosomes. DAPI-negative bands (–) corresponded to CMA+ bands. The CMA+/DAPI- bands were observed at the telomeric position of four chromosomes in H. megalanthus. When fluorescence in situ hybridization of rDNA was performed, the 18S-5.8S-25S rDNA sites were detected in telomeric positions of two chromosomes of H. undatus and H. costaricensis and four chromosomes of H. megalanthus. The 18S-5.8S-25S rDNA sites corresponded to the CMA+/DAPI- bands.