Karyotype Evolution and Genetic Variation in Date Palm (Phoenix dactylifera L.) Varieties Cultivated in Pakistan

Due to limited cytogenetic data, the date palm (Phoenix dactylifera L.), a monocotyledonous and dioecious species, previously had uncertain ploidy levels. This study aimed to determine the chromosome number and develop karyotypic profiles for elite commercial date palm cultivars cultivated across four provinces of Pakistan, with additional comparisons to exotic varieties. All analyzed cultivars were confirmed to be diploid, possessing a chromosome number of 2n = 36. Detailed karyotypic analyses were performed, including measurements of total chromosome length (TCL), lengths of short and long arms, relative length (RL), and centromeric index (CI) for each chromosome. The chromosome complements consisted of metacentric (m), submetacentric (sm), subtelocentric (st), and telocentric (t) chromosomes. Average chromosome lengths varied among cultivars, ranging from 0.99 µm to 6.46 µm. The wild genotype Wild03 exhibited a symmetric karyotype, comprising 11 metacentric, 4 submetacentric, and 3 telocentric chromosomes, suggesting a more primitive chromosomal structure. In contrast, the cultivar Asul Khurmo showed a higher number of telocentric chromosomes, indicating a more derived karyotype. These karyological insights advance our understanding of date palm cytogenetics and offer a valuable foundation for future studies on the origin, evolution, and improvement of date palm varieties.