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Certified potato seed tuber usage is one of the most important steps for production of high yield and quality potatoes. For this reason different seed tuber production methods have been developed. Among these methods, mini tuber production is the most popular one. In order to produce mini tubers, firstly potato plants are produced in vitro, and these plants are transferred to an environmentally-controlled greenhouse. Thus, disease- and virus-free mini tubers are produced as seed tubers. However, in vitro section of mini tuber production creates problems like storage and transfer of in vitro plants, and adaptation period of the plants to greenhouse conditions. In vitro micro tuber (MT) formation has been selected as a solution of these problems. The aim of the study was to produce micro tubers from 15 different genotypes and evaluate their micro tuberization performances to determine the genotype effect on MT formation. 3 varieties, 3 breeding lines and 9 different genotypes from International Potato Center (CIP) were selected for the study. For this purpose, micro tubers are produced in vitro by using Murashige and Skoog (MS) medium supplemented with 8% sucrose and 0.1 mg/L thidiazuron (TDZ). All experiments were conducted under dark conditions and 22/16 °C (8/16 h) temperature cycle. The micro tuberization performances were evaluated according to MT number per plant, MT formation rate (%), MT weight per plant (g), mean MT weight (g), mean MT diameter (mm). Differences between micro tuber production performances of different genotypes were determined and CIP395017.229 was identified as the most promising genotype to produce micro tubers.

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The development of transgenic potatoes is imperative to investigate various gene functions as well as to develop robust potato varieties resistant to different biotic and abiotic stresses. Directing a potato breeding program from cultivated tetraploids to selfcompatible diploid lines will be highly helpful for potato breeders. However, diploid potatoes are considered recalcitrant to regeneration. We aimed to develop a protocol for the transformation of diploid Solanum chacoense M6 potatoes using leaf, internodes, and microtubers as the explants. Agrobacterium tumefaciens strain GV2260 harboring pBIN19 expression vector containing gusA gene (interrupted by an intron to induce expression from eukaryotic cells) was used for this purpose. Different inoculation times (10, 20, 30 min) were applied in aforementioned explants for gene transfer. After cocultivation, explants were transferred to the media with various hormone concentrations [6-benzylaminopurine (BAP), 1-naphthaleneacetic acid (NAA), trans-zeatin, kinetin, and 2, 4-Dichlorophenoxyacetic acid (2,4-D)]. The calli generated were then transferred to shoot generating medium supplemented with thidiazuron (TDZ) and gibberellic acid (GA 3 ). According to histochemical GUS analysis, we found a 20 min inoculation time to be optimal for gene transfer and the medium containing 2 mg L -1 BAP and 2 mg L -1 NAA was the most suitable medium for callus induction from 20 min inoculated explants (41% callus formation for internodes and 65% for leaf explants). Abundant transcripts levels of gusA gene was found in primary transformants when subjected to RT-qPCR. GUS fluorometric assay further confirmed the primary transformants at protein level. The present study can serve as a gateway to transfer gene(s) of interest in diploid potatoes.

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