The author who originally aimed at the development of True Potato Seed technology in 1975, initiated the project "Flower bud differentiation and development in potato" at CIP in 1984 to analyse the basic requirements for TPS production.
First, the nature of flower bud differentiation was clarified. Then, the adverse effect of sudden changes of the air temperature and light intensity on flower development of the plant at the critical stage was analysed. The plant was likely to become very susceptible to stress two weeks after emergence. In extreme cases, the primordia of the inflorescence could not develop at all.
After various experiments on the effect of plant irradiation were carried out, it was observed that 3 h night break exerted a positive effect on flower development especially in the varieties in which the induction of flowering had been difficult by irradiation immediately after dusk or just before dawn.
The factors controlling the effect of the 3 h night break include variety, air temperature, basic photoperiod, light intensity and timing of 3 h night break and initiation and duration of the break treatment. The effects of these factors were examined and technology is proposed for TPS production under shorter photoperiod than 11.5 h at cooler air temperature.