Chromosome and Pollen Morphology of Amaranthus hybridus L. and Amaranthus retroflexus L. in Bulgaria

The chromosome and pollen morphology in the Bulgarian populations of Amaranthus hybridus L. and Amaranthus retroflexus L. was studied. The diploid chromosome number 2n = 34 was found. The metacentric type of chromosomes was predominant in all studied populations. In the karyotype of A. hybridus, the length of the metaphase chromosome ranged from 0.38 μm to 1.60 μm, and the total haploid length of the chromosome set - from 11.44 μm to 13.50 μm. The length of the chromosomes in A. retroflexus ranged from 0.18 μm to 2.27 μm, and the total haploid length of the chromosome set - from 13.01 μm to 23.32 μm. Pollen morphology was examined using a scanning electron microscope (SEM). Pollen was defined as a spherical, pantoporate type. The pollen diameter in A. hybridus varied from 18.93 μm to 22.11 μm, and in A. retroflexus - from 16.75 μm to 22.21 μm. Differences in the number and diameter of pores have been found between the two species.