Genetic Structure of Modern Durum Wheat Cultivars and Mediterranean Landraces Matches with Their Agronomic Performance

Abstract

A collection of 172 durum wheat landraces from 21 Mediterranean countries and 20 modern cultivars were phenotyped in 6 environments for 14 traits including phenology, biomass, yield and yield components. The genetic structure of the collection was ascertained with 44 simple sequence repeat markers that identified 448 alleles, 226 of them with a frequency lower than 5%, and 10 alleles per locus on average. In the modern cultivars all the alleles were fixed in 59% of the markers. Total genetic diversity was HT = 0.7080 and the genetic differentiation value was GST = 0.1730. STRUCTURE software allocated 90.1% of the accessions in five subpopulations, one including all modern cultivars, and the four containing landrace related to their geographic origin: eastern Mediterranean, eastern Balkans and Turkey, western Balkans and Egypt, and western Mediterranean. Mean yield of subpopulations ranged from 2.6 t ha-1 for the western Balkan and Egyptian landraces to 4.0 t ha-1 for modern cultivars, with the remaining three subpopulations showing similar values of 3.1 t ha-1. Modern cultivars had the highest number of grains m-2 and harvest index, and the shortest cycle length. The diversity was lowest in modern cultivars (HT = 0.4835) and highest in landraces from the western Balkans and Egypt (HT = 0.6979). Genetic diversity and AMOVA indicated that variability between subpopulations was much lower (17%) than variability within them (83%), though all subpopulations had similar biomass values in all growth stages. A dendrogram based on simple sequence repeat data matched with the clusters obtained by STRUCTURE, improving this classification for some accessions that have a large admixture. landraces included in the subpopulation from the eastern Balkans and Turkey were separated into two branches in the dendrogram drawn with phenotypic data, suggesting a different origin for the landraces collected in Serbia and Macedonia. The current study shows a reliable relationship between genetic and phenotypic population structures, and the connection of both with the geographic origin of the landraces.

Wheat: A Crop in the Bottom of the Mediterranean Diet Pyramid

“…The genetic diversity found by Soriano et al [29] was lower in the eastern Mediterranean group, indicating that the diversity of wheat increased during the dispersal from its area of domestication to the western Mediterranean Basin.…”

“…The irst diversity studies used phenotypic markers of morphological and physiological traits, but DNA-based markers are currently extensively used as they are not afected by the environment and can be detected in all tissues at all developmental stages. Among them, microsatellites or simple sequence repeats (SSRs) have proven to be very useful for evaluating the genetic diversity and population structure of Mediterranean wheat collections [17,[24][25][26][27][28][29].…”

“…A recent study by Soriano et al [29] classiied a collection of 152 durum wheat landraces and old varieties from 21 Mediterranean countries into four subpopulations that showed an eastern-western geographical patern (Figure 4): eastern Mediterranean, eastern Balkans and Turkey, western Balkans and Egypt and western Mediterranean. The genetic diversity found by Soriano et al [29] was lower in the eastern Mediterranean group, indicating that the diversity of wheat increased during the dispersal from its area of domestication to the western Mediterranean Basin.…”

Durum wheat and septoria tritici blotch: genes and prospects for breeding

“…Stb22q is the first major QTL identified in durum wheat with a wide efficacy and is therefore an important discovery that will facilitate the release (Giraldo et al 2016;). These landraces are treasured sources that were often used in wheat improvement (Lopes et al 2015;Soriano et al 2016). Alike wild durum progenitor (chapter 3), landraces convey valuable resistance genes that were used to enhance durum wheat resistance to various fungal diseases (Prat et al 2017;Rahman et al 2017), which thus stirred our interest.…”

“…Studying the genetics of resistance to Z. tritici in durum wheat cannot exclude contemporary durum cultivars or the so called semi-dwarf cultivars that are notably the most desired materials for farmers due to their improved agronomical traits, their high productivity and their genetic uniformity (Soriano et al 2016;Tadesse et al 2016) (Chapter 5). Modern cultivars constitute the outstanding outcome of the green revolution.…”