Unravelling genetic diversity and genetic structure of Senna italica Mill. in Rabigh region, Saudi Arabia

Senna italica is a perennial plant distributed in desert and subtropical regions of the world. In Rabigh Province, western Saudi Arabia, the few persisting populations of this species are exposed to many threats, including overcutting and, recently, human habitation. These threats are predicted to be exacerbated with the advancement of aridification caused by climate change. The conservation and revival of the diminished populations of S. italica requires an assessment of their genetic diversity and genetic differentiation. To accomplish this objective, we applied 10 simple sequence repeat (SSR) primer pairs, with which 10 polymorphic loci were confirmed. These polymorphic loci were used to determine the population genetics of 60 plant accessions sampled from 5 populations of S. italica located in five sites in Rabigh Province: Wadi EL Khaneg, Wadi Al Johfa, Wadi Al Hakak and Wadi Khurieba and Wadi Wadi Albaidaa . Low to moderate levels of genetic diversity were found in all populations (the values of the PPL% ranged between 51.5% and 21.5%) along with a decreased value of H_T (0.451) and a considerable inbreeding value (F= 0.4552), which verified an obvious shortage of heterozygotes. High genetic differentiation among the populations and a low level of gene flow suggest isolation among the S. italica populations, which caused a severe deficiency in gene migration. The data obtained herein will inspire several recommendations for conservation the existing populations, including seed preservation, and management of human activities. All of these actions are urgently needed to prevent imminent extinction.