Genetic diversity and population structure of modern Bulgarian and foreign durum wheat based on microsatellite and agronomic data

The genetic variation and population structure of a panel of 90 durum wheat (Triticum durum desf.) consisting of 62 varieties and breeding lines originating from two agro-ecological zones in Bulgaria (Northern and Southern Bulgaria) and 28 introduced varieties from South-western, Central and Eastern Europe, and the USA were determined by 34 microsatellite markers (SSR). The genetic diversity in the modern durum wheat was 0.5612 with 6.88 alleles per locus. Model-based population STRUCTURE analysis identified two sub-populations (K = 2) separating the South Bulgarian varieties (SP1) from all others (SP2), including South-Western, Central-Eastern European and North Bulgarian ones. Subsequent genetic structure analysis at K = 4 revealed an additional division of each sub-population into two (SP1-2, SP1-4, SP2-1, SP2-3). DAPC analysis and UPGMA dendrogram based on SSR data were in excellent agreement with the Subpopulations defined by STRUCTURE analysis. The Principal Component Analysis (PCA) revealed that among the studied 5 agronomically important traits the correlation between grain yield and plant height was the highest and distinguished 10 varieties and advanced breeding lines from Southern Bulgaria (SP1-2 and SP1-4) as most promising in regard to yield stability. This study showed a good relationship between the genetic and phenotypic population structures according to the division of the genotypes by their agro-geographical origin. It will be useful for both breeders and farmers and could serve as a fundament for durum wheat improvement programs under drought prone environmental conditions.