Flow cytometry and chromosome numbers variation in argan tree Argania spinosa (L.) Skeels

Argania spinosa L. Skeels is an endemic species of west-central Morocco, which is characterized by a high diversity of morphological and genetic traits. It constitutes a natural resource for oleo-agro-sylvo-pastoral uses. All conservation and genetic breeding strategies aimed to domesticate argan require a good knowledge of the plant material. However, several studies focused on agronomical, morphological, phytochemical, and molecular characterization, while the cytogenetic aspects were less investigated. The objective of this work is to identify the chromosome number and ploidy level on the national argan collection at the Agadir Regional Agronomic Research Center, Morocco. The determination of the chromosome number was carried out on root tips of germinated seeds collected from five trees genotypes selected on various morphological aspects. As a result, chromosome count on active root tip cells showed variation in the number (2n = 20; 2n = 22; 2n = 24) with a stable ploidy level (2n = 2x) that is confirmed by flow cytometry. These results combine two previous findings (2n=20, 2n=24) and reveal a third existence of twenty-two chromosome. As a conclusion, A. spinosa has three chromosomal numbers which represent the genetic diversity of the chromosomal number that this species exhibits. More studies are required to explain this variation on chromosome numbers for future breeding programs and to avoid incompatibilities.