Digital Theses Archive


Tesi etd-12112018-105957

Type of thesis
Novel allelic variation for wheat improvement: quality, agronomic, and adaptation traits from wild relatives and landraces
Scientific disciplinary sector
Relatore Prof. PE', MARIO ENRICO
Membro Prof.ssa ERCOLI, LAURA
Membro Prof.ssa MENSUALI, ANNA
  • wheat wild relative
  • landraces
  • GWAS
  • Landscape genomics
  • flour quality
Exam session start date
This Phd project scope was the discovery of novel variability in genomic loci of interest related to environment adaptability, agronomic and flour quality traits, through a landscape genomics approach and genome wide associations studies (GWAS) in Triticum urartu. Then we performed a seed storage protein fingerprinting on Ethiopian durum wheat landraces aiming to the identification of novel allelic variants to improve pasta quality.<br>Throughout the breeding history of wheat, evolution and domestication process lead improved varieties with a reduced genetic basis for several traits, including those related to adaptability, agronomic and flour quality traits. Nowadays, new genetic diversity might be found in the untapped allele pools of wheat wild relatives and cultivated wheatlandraces and put it at use in modern breeding efforts. Never domesticated T. urartu, the A genome donor of both tetraploid and hexaploid wheat, still posses wide allelic diversity for numerous important traits, including agronomic characteristic (Wang et al., 2017), grain quality (Yilmaz et al.,2015; Cuesta et al.,2015) and stress tolerance (Valkoun et al.,2001). Ethiopian durum wheat landraces are the result of a millennial selection applied by farmers and although several studies reported their potentiality (Klindworth et al., 2007; Teklu et al., 2009; Solomon et al.,2003) for wheat improvement they have not been systematically used in Ethiopia and international breeding programs. <br>With the aim of collecting and analyzing the highest possible genetic variability, 239 accessions were aggregated representing the real distribution of T. urartu in the Fertile Crescent. Triticum urartu collection was first genotyped using a double-digestion RAD sequencing approach and producing 56,728 high-quality SNPs markers mapped on the A genome of wild emmer (Avni et al., 2017). The diversity analyses revealed a broad molecular variation across the sampled population. Then we performed a landscape genomics analysis combining the molecular data with environmental variables (altitude, temperature, rainfall measurements) related to the sampling sites for each accession. We obtained several marker environmentassociation (MEAs) related to genomic loci involved in environmental adaptability. Finally, we performedphenotypic characterization, evaluating the distribution of different agronomic and flour quality characters and high molecular weight glutenin (HMW-GS) in T. urartu collection. The results showed a wide phenotypic variability for both field and flour phenotypes, showing a normal distribution with extreme and interesting values in the tails of distributions. Also,endosperm proteins analyses indicated the presence of highly polymorphic protein bands. The GWAS performed in order to explore and identify the genetic bases of the phenotype variability observed reported a total of 30 quantitative traits nucleotide (QTN) distributed among all T. urartu chromosomes.<br>The high variability of endosperm proteins found in Ethiopian durum wheat landraces pointed out the potential role of these materials breeding programs for flour quality. We identified twelve gliadin genotypes with a low presence of γ-42, usually associated with worst pasta quality. Glutenin alleles were highly polymorphic, with the greater variability at the LMW-GS Glu-B3 locus, resulting in 24 different combinations most of which unknown in literature. Half of our collection showed LMW-2 types, the one associated with good pasta quality. We argue that the Ethiopian landraces germplasm bears novel allelic variants for improve gluten quality and pasta production.<br>Our results show that novel allelic variability for quality traits is available in landraces and in wild relative collections. With the contribution of genomic approaches capable to identify the genetic basis of these sources of flour quality, these collections may provide wheat breeders with a new toolbox to accelerate both durum and bread wheat improvement.<br>