Rhizoctonia solani Affects the Salinity Tolerance of Potato Plants by Modulating Sugar Metabolism

Abstract In the present study, the alterations in some physiological characteristics and sucrose metabolism of Desiree, Granola, Lady Claire, and Russet Burbank potato cultivars that react differently to salt stress and Rhizoctonia solani were evaluated. The potato cultivars were challenged with 5 dS m −1 NaCl, R. solani and their combination in a pot experiment. Preferably, fully developed leaves, third from the apex, were collected at 15-day intervals. Tuber skin and tuber flesh samples were taken from fully mature tubers showing varietal characteristics. Lady Claire and Russet Burbank cultivars had the highest and lowest leaf cell-membrane injury rates, respectively. The imposed stresses generally increased the total and reduced sugar and sucrose contents of leaves compared to the control. The R. solani and R. solani + NaCl treatments caused an increase in the starch content in cvs. Desiree and Lady Claire and a reduction in Granola and Russet Burbank compared to the control treatment. The invertases were expressed at higher levels, notably during the tuber initiation and bulking stages. The expression of the leaf InvGF gene increased 11.73-fold in cv. Lady Claire, followed by cvs. Desiree, Granola, and Russet Burbank by 7.23-fold, 5.77-fold, and 5.51-fold increases, respectively, compared to the control. Lady Claire and Desiree cultivars were determined to be the cultivars with the highest relative gene expression levels in tuber tissues. Consequently, the invertases are thought to play a more important role in the tolerance of the R. solani + NaCl stress combination than sucrose synthase. Additionally, the leaf tissues were more sensitive than the tuber tissues.