CYTOGENETICS OF RUTACEAE .5. HIGH CHROMOSOMAL VARIABILITY IN CITRUS SPECIES REVEALED BY CMA DAPI STAINING

The CMA/DAPI chromosome banding pattern of six Citrus species was analysed. All of them showed a large amount of heterochromatin and heterozygosity. Most of the heterochromatin was CMA+ /DAPI - and was located mainly in the terminal region of the long arms. Each individual was heterozygous for at least one chromosome pair and each species presented a different banding pattern. The greatest amount of information on karyotype variation can be obtained from the four largest pairs. Pairs I and III showed the highest amount of heterochromatin and heterozygosity whereas pair II was highly stable and almost completely lacked CMA+ heterochromatin. On the other hand, some features common to all species suggest a strong chromosome homoeology conservation. The CMA staining revealed some chromosome markers for each Citrus species that may be very useful in the identification of zygotic versus nucellar embryos, as well as for further evolutionary studies.