An in vitro tuberization bioassay to assess maturity class of new potato clones

The maturity of a new potato clone can be determined from physiological mea surements in field trials that involve considerable time, space and work. T o improve the procedure, an in vitro bioassay based on tuberization behavio ur of potato cultivars of different maturity classes was established. Twent y-six sets of temperature, photoperiod and photosynthetic photon flux value s were assayed on the eight potato cultivars Jaerla, Zorba, Spunta, Kennebe c, Turia, Desiree, Baraka and Fenix. In vitro tuberization was influenced b y cultivar, photoperiod and temperature. The environmental condition define d by 12 h photoperiod, 34 mu mol m(-2) s(-1) of photosynthetic photon flux and 25 degreesC temperature produced statistical differences in tuberizatio n among maturity classes. Both the earliness of tuberization and the "degre e of tuberization" (based on the type of microtubers developed) permitted a ssigning a cultivar to a maturity class. Early cultivars showed higher read iness to tuberize and higher values of "degree of tuberization" than late c ultivars.