Shoot and root zone temperatures are critical in bidirectional regulation of tuberization in potato

Multiple signals regulate tuberization in potato and among them, photoperiod and temperature are most crucial. Optimum temperature for tuberization is around 20 °C and elevated temperatures above optimum drastically reduces tuberization. Our study therefore aims at understanding and establishing a system to study the effect of shoot and root zone temperatures on tuberization. Towards this, a less photosensitive cultivar, Kufri Jyoti was identified initially by analysing the allelic variations in CDF1 gene. Using the aeroponic systems housed inside the poly house, the effect of temperature on tuberization was studied. Following staggered sowing on aeroponic chambers during rabi season (Oct-Dec), the shoot zone (Sz) and root zone (Rz) were exposed to elevated mean cumulative day temperatures with one set of chambers regulated to maintain optimum temperature of 19 ± 2 °C in Rz (Rz-R) irrespective of date of sowing/ planting. With delayed planting, plants were exposed to high temperatures and our study demonstrated that, elevated temperatures in Sz and/or Rz had significant effect on growth attributes, tuber number and tuber weight per plant. While the tuber number was significantly higher under optimum root and shoot zone temperature, it was rather decreased by 3.5 and 2.3 for every degree rise in Rz (irrespective of Sz) and Sz (irrespective of Rz) temperature, respectively. However, regulating the Rz temperature inside the aeroponic chambers, reasonably a good number of mini-tubers per plant was produced regardless of the shoot zone temperatures suggesting that, root temperature is more crucial than shoot temperature. Furthermore, reduction in tuberization at elevated temperature was correlated well with reduction in expression of key positive regulators (StSP6A, StBEL5) and enhanced expression of key negative regulator, StSP5G in both leaves and solons. Taken together, our data suggest that, regulation of both root and shoot zone temperatures are important for effective tuberization and tuber yield in potato.