Development of double-haploid lines in Galia-type melons (Cucumis melo var. cantalupensis) using in vitro colchicine treatments

Melon is an important vegetable crop in the world. Cantaloupe types of melons (Cucumis melo var. cantalupensis L.) ripens early and are aromatic but they have a short shelf life, which limits transport and export opportunities. In this research, we used a total of 84 plants originating from BC₃ populations to developed 100% homozygous haploid lines by using irradiated pollen (300 Grays of Cobalt⁶⁰) technique for breeding cantaloupe melons with long shelf life. A total of 600 haploid melon lines were obtained with irradiated pollen technique. The haploid plants of these lines were propagated by in vitro micro-cuttings. In vitro colchicine (0.5%) was applied to 15 micro-cuttings of each haploid line for 2 h to double the chromosome number. After rinsing 3 times with sterile distilled water micro-cuttings were dried and transferred into test tubes contaning MS medium. Afterwards they were placed in growth chamber having 24°C temperature and 16/8 h day/night photoperiod conditions. After 1 month plants were acclimatized to greenhouse. The ploidy level was identified by morphological observations, pollen presence and chloroplast/stoma counting. Among the 600 in vitro colchicine applied haploid lines, 152 were found to be diploid and the success of in vitro duplication was obtained as 25.33%.