The response of potato (Solanum spp.) to photoperiod and light intensity under high temperatures

The growth, development and yield of seven cultivars were evaluated under field conditions with photoperiods from 11.5 to 16 hours and light intensities from full light (≧12 MJ/m2/day) to only 42% light in in 3 experiments in the Philippines. The longer photoperiod significantly delayed and reduced tuberization, promoted profuse haulm growth, resulting in: more branching, increased plant height, more flowering, many secondary stems and delayed plant senescence. ‘DTO-33’ was least affected by long photoperiod, followed by ‘Red Pontiac’ and ‘Desiree’. Shading resulted in delayed tuber initiation, taller plants, thinner stems, smaller leaves but longer canopy duration and a slightly larger canopy. ‘DTO-33’ was least affected by shading followed by ‘Desiree’, ‘LT-2’ and ’Red Pontiac’. ‘LT-5’ and ‘P-3’ suffered the greatest tuber yield reduction through shading.