South African Journal of Science
On-line version ISSN 1996-7489
MIENIE, A. and DE RONDE, J.A.. A comparison of drought stress and heat stress in the leaves and tubers of 12 potato cultivars. S. Afr. j. sci. [online]. 2008, vol.104, n.3-4, pp. 156-159. ISSN 1996-7489.
Potato yield is extremely sensitive to drought and heat stress, but there are variations in the degree to which cultivars are affected by these stresses. Strategies for the selection of stress-tolerant cultivars in a breeding programme can therefore be developed. The 2,3,5-triphenyltetrazolium chloride viability assay was evaluated to estimate drought and heat tolerance of leaves and tubers of 12 potato cultivars which differ in their response to drought. Floating leaf discs and tuber slices in 0.5 M mannitol (-1.24 MPa) simulated drought. After the drought acclimation treatment, the leaf discs were subjected to a lethal drought stress by exposure to an osmotic potential of -2.48 MPa. The viability of the leaf discs after the drought treatment was estimated spectrophotometrically by measuring the formazan concentration at 485 nm. Lower absorbance values in the control treatment, compared with the stress treatment, indicated a tolerant reaction. As drought simulation in the laboratory can differ from field conditions due to the effect of heat stress, the cultivars were also evaluated for heat tolerance. A stress index was established which can assist breeders to distinguish between plant responses to heat and drought.