A study on the molecular characterization of some commercial cotton varieties registered in Turkey

Cotton (Gossypium L.) is an important natural resource for the textile industry worldwide. Cotton is mainly cultivated in nearly 80 countries such as China, the United States, India and Uzbekistan. Cotton fibers are the main source for textile industry and its seeds are used for oil production, the meal is used as protein-rich animal feed. In addition, the short-fibers are called as linters and they used in more than 50 industries making the cotton an indispensable plant group in our country and the world. Breeding studies in cotton are generally based on hybridization of the best genotypes in term of yield and fiber quality and selections from previously developed varieties. However, cotton breeding programs are negatively affected from the narrow genetic diversity of the cultivars. The most cultivated cotton in the world is the varieties belonging to G. barbadense and G. hirsutum species known as the new world cottons and having tetraploid genome. Since the evolution of these genomes in the process of formation is not very long, genetic diversity is very narrow. In present study the genetic basis of some cotton varieties which are registered in Turkey were characterized in term of identification of genetic diversity based on molecular methods. In the study a total 192 lines / varieties registered in Turkey along with other varieties or lines registered in other countries were characterized using a total of 40 loci amplified with both genic- and genomic-SSR markers. In the studies dealing with the determination of genetic relationships among varieties, different analysis methods and statistical analyzes were utilized. In the study, Bayesian statistics were used for clustering analysis and the relationship between species was determined as 100%, while the some varieties in the species of G. hirsutum were grouped in varying places in the clusters. In addition, the genetic relationship between the varieties based on the Jaccard similarity index was investigated and 23 varieties were found to have less similarity relations than the other varieties among the 192 lines / varieties. These varieties included ADN 413, Ashgabat 91, BA 119, BA 525, Crema 111, Delcerro, Delcot 311, Diva, DP 332, DP 419, Gloria, Airless, Korina, Ligur, Lockette , Napa 122, Nazilli 66-100, Nihal, Sealand 542, ST 213, Stardel, Tashkent 1 and Green Fiber. The genetic relationship between these varieties ranged between 54.5% and 70%. The use of these varieties in breeding studies would be advantageous in the detection of heterosis. In the PCoA analysis of 192 lines / varieties used in the present study, the varieties of G. hirsitum species were divided into four (4) main groups. In these groupings, it was found that long fiber producing varieties were found in the group called Group1, and Group 2 also had close varieties. However, the genetic similarities between the groups Group3 and Group4 were found to be less than the first two groups. As a result, the varieties that have been registered in different countries and registered in Turkey were found to have narrow genetic base. In order to better identify the genetic relationship between these varieties, more markers with capilary systems for separation should be used. Finally, it was concluded that cross-breeding among cotton plant varieties/lines belonging different species should be performed in order to increase the narrow genetic diversity.