Abstract

Abstract

Karyotype analysis is a vital technique in plant cytogenetics, offering insights into chromosomal structures, species differentiation, and evolutionary relationships. This study focused on three Annona species L.—Annona muricata L., Annona squamosa L. and Annona senegalensis Pers collected from Abia State, Nigeria, with the goal of characterizing their chromosomal features and assessing cytogenetic variation. Root tip cells were prepared using squashing and staining techniques, and chromosomes were analyzed under an Amscope microscope with a 1000MA (milliamp) camera. All species were found to be diploid (2n) with a somatic chromosome number of 2n = 2x = 14. Chromosome measurements revealed slight variations among the species: total chromosome lengths ranged from 3.066 µm (microns) in A. squamosa to 3.142 µm in A. senegalensis; short arm lengths varied between 1.234 µm in A. squamosa to 1.344 µm in A. muricata; and long arm lengths varied between 1.789 µm in A. muricata to 1.834 µm in A. squamosa. The centromeric index ranged between 1.906 µm in A. squamosa and 2.095 µm in A. muricata, while the arm ratio was highest in A. squamosa (1.486 µm) and lowest in A. muricata (1.331 µm). R-values varied from 0.672 µm to 0.751 µm. These karyotypic differences, although subtle, are significant for species delimitation and may inform strategies for genetic improvement and conservation. The study highlights the potential of cytogenetic markers in supporting the taxonomy and sustainable use of underutilized tropical fruit crops like Annona.