Genetic diversity of Turkish commercial cotton varieties revealed by molecular markers and fiber quality traits

To assess the genetic diversity and relationships among commercial Gossypium species released in Turkey between 1964 and 2014, 96 cotton varieties were analyzed using morphological and molecular markers. Morphological analysis was performed based on 4 fiber quality traits including fiber length, strength, fineness, and uniformity, and the mean values of each trait for each genotype were calculated using 2-year data. The results showed that most of the genotypes have long fiber length, very high fiber strength, coarse (45 genotypes) or average (50 genotypes) fiber fineness, and high uniformity. Twenty-six simple sequence repeat (SSR) markers and 14 markers linked to quantitative trait loci (QTLs) for fiber quality traits produced a total of 103 alleles, with an average of 2.57 alleles per locus ranging from 80 bp to 300 bp products, with an average polymorphism information content (PIC) value of 0.233. Markers DPL513 and DPL431 (among 26 SSR markers) and markers CIR246 and BNL4108 (among 14 molecular markers) were found to be very informative, with 0.724, 0.663, 0.749, and 0.583 PIC values, respectively. The combined morphological and molecular data analysis resulted in more than 8 clades using the unweighted pair group method with arithmetic average (UPGMA). The upland cotton varieties were distinctly separated from the lowland cotton variety Maydos Yerlisi (Gossypium herbaceum L.). Within the upland cotton varieties, the Egyptian cotton variety Giza 70 (G. barbadense L.) was distinctly separated from commercial cotton varieties of Turkey (G. hirsutum L.), as revealed by both morphological and molecular dendrograms. Principal component analysis (PCA) derived from combined data was in agreement with UPGMA analysis. It is concluded that commercial Turkish cotton varieties have a good genetic diversity with high fiber quality, considering the upland cotton's narrow genetic structure. These results can provide a useful guide for selecting specific germplasm with distinct genetic backgrounds in cotton breeding programs.