Effect of temperature and sucrose on Ulluco (Ullucus tuberosus Caldas) microtuber production under neutral photoperiodic conditions

The area of the Andean Mountains is characterized by a high level of biodiversity. The species Ullucus tuberosus, which belongs to the Andean Root and Tuber Crop group, has a prominent role in feeding local communities. Despite its importance, little information on the basic aspects of this crop is available and its unknown genetic wideness is at risk to disappear. This study was conducted in order to delineate the effect of both temperature and medium sucrose concentration on Ulluco microtuber production. In fact microtubers represent an efficient way to preserve germplasm and thus the definition of simple protocols for microtuber induction is a valid tool to guarantee germplasm conservation and its economic sustainability. Three levels of sucrose (30, 60 and 90 g l-1) in the Murashige-Skoog medium and two temperature growth conditions (12-18°C and 18-24°C) have been chosen to assess microtuber production in Ulluco. The 3% sucrose concentration and the 12-18°C temperature range determined the highest microtuber number. The sucrose effect on microtuber induction is in contrast to what has been observed in other species, such as Solanum tuberosum and Dioscorea composita. Low sucrose concentration and temperature are also associated with high microtuber dormancy levels. The 18-24°C temperature range and the 3% sucrose concentration induced a higher plant development in terms of fresh plant and tuber weight.