Assessment of genetic diversity in Tunisian populations of Medicago polymorpha based on SSR markers

Loua Haddoudi1, 2, Sabrine Hdira1, 2, Najah Ben Cheikh1, Asma Mahjoub1, Chedly Abdelly1, Ndiko Ludidi3, 4, and Mounawer Badri1*
Medicagopolymorpha L. is a herbaceous legume that can be a useful pasture crop, especially in Mediterraneanclimates. This study aimed to analyze the genetic variation in five populations of M. polymorpha collected from different eco- geographic regions in Tunisia using eight SSR markers. The transferability of 112 SSR markers distributed on the eight chromosomesofM.truncatula Gaertn. showed that 50 SSR markers could be amplified in M.polymorpha. Amongthese 50 SSR markers, eight (8) markers were polymorphous. A high level of polymorphism (126 polymorphic alleles with an average of 5.3 alleles per locus) and a moderate level of genetic diversity were found in all the studied populations, with observed and expected heterozygosities averaging between 0 and 0.69, respectively. Results from analysis of molecular variance (AMOVA) revealed that the most variation was found within populations (76%). Moderate levels of population differentiation (FST = 0.12 to 0.19) accompanied by a high rate of gene flow between populations (Nm = 1.08 to 1.83) were recorded. This molecular differentiation (FST) was not dependent on geographical distances (r = 0.395, p = 0.524), suggesting that studied populations are not geographically isolated. Our results showed that studied populations were clustered in to three groups. A first group is formed by the populations of El Kef (TNP7) and Bulla Regia (TNP9), asecond group of Enfidha (TNP1) and a third group of Soliman (TNP8) and Mateur (TNP11). Results obtained in our study could be helpful for breeders considering introduction of some lines of this species into M. polymorpha breedingprograms.
Keywords: Gene flow, FST, Medicago polymorpha, SSR markers, Tunisian populations.
1Centre of Biotechnology of Borj Cedria, Laboratory of Extremophile Plants, B.P. 901, Hammam-Lif 2050, Tunisia.
*Corresponding author (mounawer.badri@cbbc.rnrt.tn).
2University of Tunis El Manar, Faculty of Mathematical, Physical and Natural Sciences of Tunis, Campus Universitaire El-Manar, 2092 El Manar Tunis, Tunisia.
3University of the Western Cape, Department of Biotechnology, Robert Sobukwe Road, Bellville, 7530, South Africa.
4University of the Western Cape, DSI-NRF Centre of Excellence in Food Security, Robert Sobukwe Road, Bellville, 7530, South Africa.