Application of Fluorescent Staining of Chromosomes to Genetic Studies in Citrus

The application of staining with the guanine-cytosine specific fluorochrome chromomycin A3 (CMA) of citrus chromosomes to genetic studies is reviewed. When CMA staining is performed, the existence of characteristic CMA banding patterns with high levels of diversity and heterozygosity in citrus chromosomes is demonstrated. Similar CMA banding patterns have been observed in related species. Thus, CMA banding patterns of chromosomes have been considered to provide very important information for phylogenic studies in citrus. Chromosomal identification of citrus has also progressed rapidly by means of the CMA banding method. Chromosomes exhibiting the same CMA banding pattern were separated and classified using the relative sizes of fluorescent bands as indices. All nine chromosomes of haploid citrus were identified by this method. Analysis of the chromosomal configuration of parental materials and their progeny was efficient for genetic improvement in citrus. Characteristic chromosomes could be used as a marker for the parent-progeny relationship since these chromosomes are transmitted from the parents. In particular, CMA chromosome staining is a very powerful tool for ploidy manipulation. The advantage of using CMA staining is that the entire chromosomal configuration can be clearly observed at once. _____________________________________________________________________________________________________________