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Determination of Optimal Doses of Plant Growth Regulators for In vitro Propagation of Four Potato Varieties (Solanum tuberosum) in Niger

Aims: The main limitation of the production of potatoes (Solanum tuberosum L.) in Niger is the external dependence on the supply of quality seeds. In the context of a national potato seed system, one of the critical phases is the rapid in vitro multiplication of virus-free good quality potato plantlets. Fifteen hormonal combinations were formulated and tested to determine a suitable hormonal combination and optimum concentrations for the in vitro production of a high number of plantlets for four farmer-preferred varieties in Niger (ATLAS, PAMELA, STEMSTER and YONA). 
Study Design:  A completely randomized design (CRD) was employed to reveal the performance of four potato varieties, as affected by fourteen combinations of NAA and BAP with four replications. Results of the study were subjected to the analysis of variance, and significant differences among treatments were determined using GENSTAT12.01. Segregation between means was made according to the Student Newman-Keuls test, at 5% threshold. 
Place and Duration of Study: The experiment was carried out at the laboratory of Biotechnology and plant improvement of the institute of radio-isotopes in the University Abdou Moumouni of Niamey, in Niger (latitude 13°29' North and longitude 2°10' Est), for 28 days. 
Methodology: Uninodal stem explants of in vitro plantlets were cultured on full-strength Murashige and Skoog media (MS) supplemented with fourteen different combinations of α-Naphthalene Acetic Acid NAA (0; 0.25; 0.50; 1.0; 2.0 mg/l) and Benzyl Amino Purine BAP (0; 0.25; 0.50 mg/l), for 28 days. 
Results: Statistical analysis of the results showed that the variety and hormonal significantly influenced the height of the plant, the number of leaves and number of roots. Treatments with NAA alone without BAP stimulated rhizogenesis. From a NAA concentration of 0.25 to 0.5 mg/l there is a proliferation of the roots and from 1 mg/l there is an increase in roots length. PAMELA and ATLAS cultivars showed better root production.