Comparative Genetic Analysis of Durum Wheat Landraces and Cultivars Widespread in Tunisia.

The durum wheat (Triticum turgidum L. ssp. durum Desf.) landraces constitute a useful natural germplasm to increase the genetic diversity in the modern durum cultivars. The Tunisian durum germplasm constitutes 28 accessions conserved in Genebank of Tunisia, which are still unexplored. In this study, a comparative genetic analysis was performed to investigate the relationships between the Tunisian durum lines and the modern cultivars and detect divergent loci involved in breeding history. The genetic diversity analyses carried out using nine morphological descriptors and the 25K single-nucleotide polymorphism (SNP) array allowed us to distinguish two groups of Tunisian landraces and one of durum cultivars. The analysis of molecular variance and diversity indices confirmed the genetic variability among the groups. A total of 529 SNP loci were divergent between Tunisian durum landraces and modern cultivars. Candidate genes related to plant and spike architecture, including FLOWERING LOCUS T (FT-B1), zinc finger CONSTANS, and AP2/EREBPs transcription factors, were identified. In addition, divergent genes involved in grain composition and biotic stress nucleotide-binding site and leucine-reach repeats proteins and disease resistance proteins (NBS-LRR and RPM) were found, suggesting that the Tunisian durum germplasm may represent an important source of favorable alleles to be used in future durum breeding programs for developing well-adapted and resilient cultivars.

Genetic Structure Analysis of a Collection of Tunisian Durum Wheat Germplasm.

The Tunisian durum wheat germplasm includes modern cultivars and traditional varieties that are still cultivated in areas where elite cultivars or intensive cultivation systems are not suitable. Within the frame of a collection program of the National Gene Bank of Tunisia (NGBT), durum wheat germplasm was collected from different Tunisian agro-ecological zones. The collected samples were studied using simple sequence repeats (SSRs) markers to explore the genetic diversity and evaluate the genetic structure in Tunisian germplasm. The results demonstrated significant diversity in the Tunisian durum wheat germplasm, with clear differentiation between traditional varieties and modern cultivars. The population structure analysis allowed the identification of five subpopulations, two of which appear to be more strongly represented in germplasm collected in central and southern Tunisia, where environmental conditions at critical development phases of the plant are harsher. Moreover these subpopulations are underrepresented in modern varieties, suggesting that traits of adaptation useful for breeding more resilient varieties might be present in central and southern germplasm. Moreover, our results will support, the activity of in situ on farm conservation of Tunisian durum wheat germplasm started by the National Gene Bank of Tunisia along with the ex situ approach.

Diversity of tunisian bread wheat genotypes revealed by morpho-agronomical and microsatellite markers / Diversidade de genótipos de trigo tunisiano para panificação obtida por marcadores morfo-agonômicos e microsatélites

The genetic diversity of a set of 21 hexaploid wheat germplasm from the National Agronomic Institute of Tunisia were investigated by applying 26 agro morphological traits and 10 wheat microsatellites molecular markers (Simple Sequence Repeat). The morphological variability was analyzed using the Principal Component Analysis (PCA) and the cluster analysis based on ward's method and square Euclidean distance. Eighteen microsatellites primer pairs were tested for all genotypes, among them 10 primers generated polymorphic and reproducible profiles. They revealed a total of 414 reducible bands among which 373 were polymorphic. The polymorphic information content (PIC) values per locus varied from 0,33 to 0,94 with an average of 0,72. Genetic similarity values between genotypes, calculated by the molecular derived data, were used to produce a dendrogram. The genotypes were clustered in four clear groups according to their origin, pedigree and in some cases to phenotypic characters similarities.

A diversidade genética de um conjunto de 21 hexaplóides em germoplasma de trigo oriundo do Instituto Nacional da Tunísia foi investigada pela aplicação de 26 caracteres morfológicos e 10 marcadores de microsatélites (Sequências simples repetidas). A variabilidade morfológica foi analisada pelo uso da análise de componentes principais (ACP) e análise de agrupamento baseada no método de Ward e o quadrado da distância Euclidiana. Dezoito primers de microsatélites foram testados para todos os genótipos, entre os quais 10 geraram polimorfismo e grupos distintos. Eles demonstraram um total de 414 bandas entre as quais 373 foram polimórficas. Os valores de polimorfismo encontrados por locus (VPL) variaram entre 0,33 a 0,94 com uma média de 0,72. Os valores da similaridade genética calculada para os dados moleculares originaram um dendograma. Os genótipos foram agrupados em quatro grupos de acordo com sua origem, pedigree (descendência) e em alguns casos pelos caracteres da similaridade fenotípica.