Selection of an efficient in vitro micropropagation and regeneration system for potato (Solanum tuberosum L.) cultivar Desirée
Sprouts of about 40 to 80 mm length were excised, surface sterilized with 70% CloroxR and cultured on solid full-strength Murashige and Skoog (MS) medium. Shoot nodal segments (1.0 cm) from in vitro plantlets (2 to 4 weeks old) were multiplied through periodic subculturing on full-strength MS medium with 30 g/L sucrose, 100 ml/L myo-inositol and 0.5 ml/L silver thiosulfate. The shoots were rooted on the same medium. Microtubers were stimulated on MS medium supplemented with 80 g/L sucrose, 100 ml/L myo-inositol and 5 ml/L benzyl adenine. They generally originate on aerial etiolated shoots producing . 1.0 } 0.5 microtuber/explant with diameter approx. 3 to 10 mm. Shoot regeneration was performed from tuber discs, internodes and leaf explants using 6 different media. Different regeneration capacities were observed by the explants along 60 days. The average number of shoots was highest from tuber discs (6.2) than from leaf explants (2.6) which exceeds about three times; no shoot from internode explants cultured on the various media. Regenerated plantlets produced from both tuber discs and leaf explants exhibited random amplification of polymorphic DNA (RAPD) analysis using five selected primers to detect somaclonal variation. All the morphological variants were excluded. One of the regenerated plantlet derived from leaf-explants was true-to-type to the main in vitro plantlet, so it will be used as a source of explants for transformation experiments. The other regenerated plantlets derived from leaf explants and tuber discs show the presence and/or absence of polymorphic bands. Results also showed that microtubers were initiated on the etiolated shoots of the regenerants at the first 10 days. The etiolated shoots induced about 2.6 } 0.6 and 2.2 } 0.5 microtuber/explants.
Key words: Solanum tuberosum L., seed tuber, sprouting, micropropagation, microtubers, explants, regeneration, random amplification of polymorphic DNA (RAPD).