GENOTYPIC INFLUENCE ON IN-VITRO INDUCTION, DORMANCY LENGTH, ADVANCING AGE AND AGRONOMICAL PERFORMANCE OF POTATO MICROTUBERS (SOLANUM-TUBEROSUM L)

Microtubers of 13 cultivars, largely grown in Italy and other European countries, were induced. They were stored in the dark at 3 degrees C for different periods (28, 56, 84 and 105 days), prior to being transferred to 20 degrees C for between 4 and 17 weeks. Following removal to room temperature, sprouting was recorded and dormancy duration quantified. Dormancy decreased from 28.1 to 19.9, 11.1 and 7.8 days with reduced time of storage. Cvs Arsy, Nicola and Jaerla took consistently more time for dormancy release. The dormancy duration was linearly and inversely correlated with the length of storage. After sprouting, tubers were held at 20 degrees C for various intervals and a range of physiological ages (0, 368, 720 and 1008 degree days) were accumulated. The field comparison of microtubers evidenced a plant growth response and tuber yield/plant affected by the cultivar and physiological age. In early cultivars (Jaerla), a better performance was shown by younger tubers; the opposite trend was noted in Alpha (a later cultivar) with an increase in stems/plant, tubers/plant and tuber yield/plant for tubers with greater physiological age. Like conventional seed tubers, microtubers showed differences in optimum physiological age associated with cultivar earliness. This study has provided some indications on how to enhance emergence and haulm development of plants from microtubers.