Cytological Characterization of Brazilian Green Dwarf Coconut (Cocos nucifera L.) via Meiosis and Conventional and Differential Karyotyping

The objective of this study was to characterize the Brazilian green Dwarf coconut (Cocos nucifera L.) by meiotic analysis and by conventional and differential karyotyping (CMA/DAPI and telomeric FISH). Sixteen pairs of bivalent were observed in the meiosis, indicating that the species is diploid and has 2n=2x=32 chromosomes. Some abnormalities were observed, such as asynchronous division and anaphase with converging fibers. The estimated recombination rate for this species was 17.04, equivalent to an average of 1.06 chiasmata per bivalent. The meiotic index was 79% and the pollen viability was 89.5%, both values considered satisfactory. The conventional karyotyping validated the observed number of chromosomes in the meiosis, i.e., 2n=32 chromosomes. The length of chromosomes ranged from 5.57 mu m to 2.13 mu m. The karyotype was considered asymmetric, with 11 metacentric and five submetacentric chromosomes pairs. The CMA/DAPI banding revealed terminal blocks in two chromosome pairs (one metacentric and one submetacentric), which was coincident with the nucleolus organizing region (NOR), and allowed the satellite characterization, which had 1.36 mu m (chromosome 4) and 0.85 mu m (chromosome 7). The telomeric FISH revealed signs only in the terminal region in all chromosomes, suggesting that this species has undergone no structural rearrangement of chromosomes during its evolution and that the telomeres of the coconut chromosomes are Arabidopsis type (TTTAGGG).