Production of tetraploid plants of some citrus genotypes

Improving new seedless citrus varieties is currently the main aspect of citrus breeding programs for both our country and the world. Triploid plants can be recovered directly from artificial and spontaneous mutations as well as crosses between two diploid genotypes resulting from the fertilization of 2n megagametophyte or by hybridization between diploid and tetraploid parents. Thus, production of tetraploid plants which are not naturally found in citrus germplasm has a great importance in terms of seedlessness breeding studies. This study covers production of tetraploid plants for parental usage in order to improve new varieties by ploidy manipulation. Buds of Clementine 22D, W. Murcott and Moro blood orange were used as plant material and effects of colchicine treatments on production of tetraploid forms of these genotypes were investigated. In this purpose, scion buds were treated with colchicine at concentration levels of 0.0%, 0.2%, 0.4%, 0.6% and 0.8% for 4, 6 and 8 hours. After treatments, survival rate (%) of plants was recorded and ploidy levels of the plants were determined by flow cytometry analysis. In addition, stomatal observations were recorded such as stomata density, length, width, size and index on the leaves of tetraploid plants in order to compare them with the observations of diploid plants. As a result of the study one tetraploid plant of Clementine 22D mandarin was recovered from the 0.4% colchicine treatment for 6 hours. Besides, mixoploid (2x+4x) forms of W. Murcott mandarin and Moro blood orange were recovered