Low Genetic Differentiation and Evidence of Gene Flow among Barley Landrace Populations in Tunisia

Abstract

Tunisian barley (Hordeum vulgare L.) landraces, representing the oldest cultivated accessions, are growing in scattered populations across drought‐ and salt‐stressed environments and constitute a precious reservoir of potentially useful traits for breeding programs. The objective of this study was to elucidate genetic diversity and population structure of barley landraces across the landscape of Tunisia. Populations from 11 geographic zones were genotyped using 21 nuclear microsatellites. A high level of genetic polymorphism with 170 detected alleles was recorded among the studied genotypes. The average allelic richness was 8.095 alleles per locus. The index of genetic diversity (He) showed an average of 0.741. Genetic diversity was very high within populations, whereas differences among populations were difficult to detect. Only 0.15% of the DNA variation was apportioned among landraces (P < 0.001), whereas 99.85% of the DNA variation was maintained within these landraces. A high gene flow (Nm) was revealed among the investigated populations, which has been facilitated by exchange of barley seeds between Tunisian cereal farmers of different regions. Genetic diversity within Tunisian barley landrace germplasms may help to maintain adaptation to a broad range of environmental conditions and provide genetically diverse resources for barley breeders. Both ex situ (seed banks) and in situ (on‐farm) conservation strategies may be required to maintain barley landrace genetic resources.

Labelling Selective Sweeps Used in Durum Wheat Breeding from a Diverse and Structured Panel of Landraces and Cultivars

“…However, the lowest gene flow was found between eastern Mediterranean landraces and the germplasms from CIMMYT and ICARDA and between these germplasms and the modern cultivars from north America. This agrees with the results reported by Parzies et al [ 51 ] and Ben-Romdhane et al [ 52 ], suggesting that the genetic differentiation among landrace SPs is due to farmer trade and is mainly influenced by geographic distances. Cultivars with a CIMMYT/ICARDA origin reported lower values of gene flow than the other SPs, as reported previously by Rufo et al [ 46 ] in bread wheat.…”

Conservation priorities for endangered coastal North African Pennisetum glaucum L. landrace populations as inferred from phylogenetic considerations and population structure analysis

“…Low genetic differentiation values were accompanied by considerable gene flow levels, which are confirmed by previous investigations concerning pearl millet landraces (Bashir et al 2015) and other crop species such as barley (Ben Romdhane et al 2017). This finding is expected especially for a highly allogamous species like P. glaucum L, which present an out-crossing rate higher than 85%.…”

From landraces to improved cultivars: Assessment of genetic diversity and population structure of Mediterranean wheat using SNP markers

“…These results are in agreement with population structure and neighbour-joining clustering, in which a higher level of admixture was found for landraces from different geographical regions. Accordingly, it has also been suggested that the low genetic differentiation among SPs is due to seed exchange by farmers, mainly influenced by geographic distances [49, 50]. When two SPs were compared, in general gene flow between landrace SPs was also higher than between modern cultivars.…”