Chromomycin A3 banding and chromosomal mapping of 45S and 5S ribosomal RNA genes in bottle gourd

Ribosomal DNAs and various banding patterns are landmarks in molecular cytogenetics providing useful information for karyotyping and addressing individual chromosomes. Bottle gourd is the only cultivated species of the Lagenaria genus with high genetic diversity. After CMA3/DAPI fluorochrome banding we investigated the GC- and AT-rich regions in interphase nuclei of five different local accessions. Fluorescence in situ hybridization (FISH) was conducted to determine the number and location of 45S and 5S rDNAs in bottle gourd. Our results showed four strong CMA3 regions in interphase and on mitotic metaphase chromosomes. FISH revealed four strong signals of 45S rDNA at the termini of two metaphase chromosome pairs and terminal 5S rDNA signals at another pair of chromosomes. The presence of four positive CMA3 bands colocalizes with four 45S rDNA signals in all bottle gourd accessions. Our results allow distinguishing two out of eleven chromosome pairs of bottle gourd.