Dataset Information

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

ABSTRACT: 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.

SUBMITTER: Slim A

PROVIDER: S-EPMC6651592 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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

Slim Amine A Piarulli Luciana L Chennaoui Kourda Houda H Rouaissi Mustapha M Robbana Cyrine C Chaabane Ramzi R Pignone Domenico D Montemurro Cinzia C Mangini Giacomo G

International journal of molecular sciences 20190709 13

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 geneti ...[more]

PMID: 31323925

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Project description:BackgroundTunisia is considered a secondary center of diversification of durum wheat and has a large number of abandoned old local landraces. An accurate investigation and characterization of the morphological and genetic features of these landraces would allow their rehabilitation and utilization in wheat breeding programs. Here, we investigated a diverse collection of 304 local accessions of durum wheat collected from five regions and three climate stages of central and southern Tunisia.ResultsDurum wheat accessions were morphologically characterized using 12 spike- and grain-related traits. A mean Shannon-Weaver index (H') of 0.80 was obtained, indicating high level of polymorphism among accessions. Based on these traits, 11 local landraces including Mahmoudi, Azizi, Jneh Khotifa, Mekki, Biskri, Taganrog, Biada, Badri, Richi, Roussia and Souri were identified. Spike length (H' = 0.98), spike shape (H' = 0.86), grain size (H' = 0.94), grain shape (H' = 0.87) and grain color (H' = 0.86) were the most polymorphic morphological traits. The genetic diversity of these accessions was assessed using 10 simple sequence repeat (SSR) markers, with a polymorphic information content (PIC) of 0.69. Levels of genetic diversity were generally high (I = 0.62; He = 0.35). In addition, population structure analysis revealed 11 genetic groups, which were significantly correlated with the morphological characterization. Analysis of molecular variance (AMOVA) showed high genetic variation within regions (81%) and within genetic groups (41%), reflecting a considerable amount of admixture between landraces. The moderate (19%) and high (59%) levels of genetic variation detected among regions and among genetic groups, respectively, highlighted the selection practices of farmers. Furthermore, Mahmoudi accessions showed significant variation in spike density between central Tunisia (compact spikes) and southern Tunisia (loose spikes with open glume), may indicate an adaptation to high temperature in the south.ConclusionOverall, this study demonstrates the genetic richness of local durum wheat germplasm for better in situ and ex situ conservation and for the subsequent use of these accessions in wheat breeding programs.

Project description:BackgroundDurum wheat (Triticum turgidum L. ssp. durum Desf. Husn) is the main staple crop used to make pasta products worldwide. Under the current climate change scenarios, genetic variability within a crop plays a crucial role in the successful release of new varieties with high yields and wide crop adaptation. In this study we evaluated a durum wheat collection consisting of 197 genotypes that mainly comprised a historical set of Argentinian germplasm but also included worldwide accessions.ResultsWe assessed the genetic diversity, population structure and linkage disequilibrium (LD) patterns in this collection using a 35 K SNP array. The level of polymorphism was considered, taking account of the frequent and rare allelic variants. A total of 1547 polymorphic SNPs was located within annotated genes. Genetic diversity in the germplasm collection increased slightly from 1915 to 2010. However, a reduction in genetic diversity using SNPs with rare allelic variants was observed after 1979. However, larger numbers of rare private alleles were observed in the 2000-2009 period, indicating that a high reservoir of rare alleles is still present among the recent germplasm in a very low frequency. The percentage of pairwise loci in LD in the durum genome was low (13.4%) in our collection. Overall LD and the high (r2 > 0.7) or complete (r2 = 1) LD presented different patterns in the chromosomes. The LD increased over three main breeding periods (1915-1979, 1980-1999 and 2000-2020).ConclusionsOur results suggest that breeding and selection have impacted differently on the A and B genomes, particularly on chromosome 6A and 2A. The collection was structured in five sub-populations and modern Argentinian accessions (cluster Q4) which were clearly differentiated. Our study contributes to the understanding of the complexity of Argentinian durum wheat germplasm and to derive future breeding strategies enhancing the use of genetic diversity in a more efficient and targeted way.

Project description:BackgroundSeptoria tritici blotch (STB), caused by Zymoseptoria tritici (Z. tritici), is an important biotic threat to durum wheat in the entire Mediterranean Basin. Although most durum wheat cultivars are susceptible to Z. tritici, research in STB resistance in durum wheat has been limited.ResultsIn our study, we have identified resistance to a wide array of Z. tritici isolates in the Tunisian durum wheat landrace accession 'Agili39'. Subsequently, a recombinant inbred population was developed and tested under greenhouse conditions at the seedling stage with eight Z. tritici isolates and for five years under field conditions with three Z. tritici isolates. Mapping of quantitative trait loci (QTL) resulted in the identification of two major QTL on chromosome 2B designated as Qstb2B_1 and Qstb2B_2. The Qstb2B_1 QTL was mapped at the seedling and the adult plant stage (highest LOD 33.9, explained variance 61.6%), conferring an effective resistance against five Z. tritici isolates. The Qstb2B_2 conferred adult plant resistance (highest LOD 32.9, explained variance 42%) and has been effective at the field trials against two Z. tritici isolates. The physical positions of the flanking markers linked to Qstb2B_1 and Qstb2B_2 indicate that these two QTL are 5 Mb apart. In addition, we identified two minor QTL on chromosomes 1A (Qstb1A) and chromosome 7A (Qstb7A) (highest LODs 4.6 and 4.0, and explained variances of 16% and 9%, respectively) that were specific to three and one Z. tritici isolates, respectively. All identified QTL were derived from the landrace accession Agili39 that represents a valuable source for STB resistance in durum wheat.ConclusionThis study demonstrates that Z. tritici resistance in the 'Agili39' landrace accession is controlled by two minor and two major QTL acting in an additive mode. We also provide evidence that the broad efficacy of the resistance to STB in 'Agili 39' is due to a natural pyramiding of these QTL. A sustainable use of this Z. tritici resistance source and a positive selection of the linked markers to the identified QTL will greatly support effective breeding for Z. tritici resistance in durum wheat.

Dataset Information

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

Publications

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

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