Schematic overview of how tuber size, tuber number and indirectly total tuber weight were affected by light and temperature, with + indicating an increasing effect on the tuber trait, and − indicating a decreasing effect. Increasing the difference in day/night temperature led to an increase in tuber size, while increasing the average temperature reduced tuber size as well as tuber number. Changes in the light spectrum affected tuber number: increasing the percentage of far-red light in the spectrum led to a higher tuber number. Also increasing the light intensity led to an increase in tuber number.

Abstract

Growing small seedling tubers from true seed, comparable with mini tubers, in controlled conditions could be a method to multiply healthy starting material of potato. In indoor farming systems, the conditions can be optimised for high production. In field trials, it is impossible to investigate the effects of environmental factors such as temperature and light separately. In this study, we performed three climate room experiments in which the effects of light intensity, temperature and percentage of far-red light in the light spectrum on tuber production were assessed. We found that increasing the average temperature reduced tuber number and tuber weight. Increasing the diurnal temperature variation while keeping the average temperature equal resulted in increased tuber size. The light treatments on the other hand only affected the number of tubers per plant: increasing light intensity and increasing the percentage of far-red light in the spectrum enhanced the number of tubers. Moreover, interaction in tuber production between inbred lines and temperature was significant, with some inbred lines being relatively tolerant to high temperature. These findings will help breed for heat tolerant varieties and optimise growing conditions for tuber production in indoor farming systems.