Durum Wheat Landraces from East and West Regions of the Mediterranean Basin Are Genetically Distinct for Yield Components and Phenology

Abstract

Genetic diversity of durum wheat landraces is a powerful tool for the introgression of new alleles of commercial interest in breeding programs. In a previous study, our team structured a collection of 172 durum wheat landraces from 21 Mediterranean countries in four genetic populations related to their geographical origin: east Mediterranean (17), east Balkan and Turkey (23), west Balkan and Egypt (25), and West Mediterranean (73), leaving 34 genotypes as admixed, and association mapping was carried out for important agronomic traits. Using a subset of this collection, the current study identified 23 marker alleles with a differential frequency in landraces from east and west regions of the Mediterranean Basin, which affected important agronomic traits. Eastern landraces had higher frequencies than the western ones of alleles increasing the number of spikes (wPt-5385 on chromosome 1B), grains per m² (wPt-0841 on chromosome 7B), and grain filling duration (7 significant marker trait associations). Eastern landraces had higher frequencies of marker alleles located on chromosomes 4A, 5B, and 6B associated with reduced cycle length, and lighter grains than the western ones. Also for lower kernel weight, four marker alleles were located on chromosome 1A. Breeders may use the molecular markers identified in the current study for improving yield under specific Mediterranean environments.

Keywords: Mediterranean basin; association mapping; cycle length; marker assisted selection; yield components.

Figure 1

(A) Graphical genotyping for the selected eastern and western Mediterranean durum wheat landraces. Shown are the country of origin of the landraces, the membership coefficient (q) of the subpopulation (SP, EM = East Mediterranean, WM = West Mediterranean) of each landrace as reported by Soriano et al. (2016). Alleles present on each landrace are indicated by colors: Blue, west; red, east; white, not determined. (B) Map of the Mediterranean Basin highlighting the countries of origin of the landraces, indicating the number of landraces from each country.

Figure 2

Marker allele frequencies specific to landraces from east and west of the Mediterranean Basin for the analyzed traits. All the significant markers shown in Table 2 and Figure 1 are included. NSm², number of spikes per m²; NGm², number of grains per m²; TKW, thousand grain weight (g); DSB, days from sowing to booting; DBA, days from booting to anthesis; GFD, grain filling duration (days).