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Poster: Biology & Disease Mgmt: Genetics of Resistance


Chemical association of potato susceptibility to Rhizoctonia solani
X. Y. ZHANG (1, 2), H. H. Jiang (2), J. J. Hao (2); (1) College of Agronomy, Inner Mongolia Agricultural University, Hohhot, China; (2) School of Food and Agriculture, University of Maine, Orono, ME, U.S.A.

Rhizoctonia solani is the causal agent of stem canker and black scurf of potato. To investigate chemical factors related to potato resistance to R. solani, 17 cultivars of potato were selected for a two-year field trial. Sixty-day-old plants were dug from field, and wax content of underground stems was measured. For other chemical measurement, potato seedlings grown in Murashige and Skoog medium to an approximate height of 12 cm, were transferred into greenhouse pots containing vermiculite and soil (v:v = 1:1). After 30 days, plants were dug and the underground stems were used to determine the silicon content. Leaves were used to determine the content of soluble sugar, soluble starch, free amino acid and soluble protein. Black scurf was measured based on 0 to 5 scale, which was used for disease index calculation. Wax content of underground stems of field-grown potato was negatively correlated with disease index (r = -0.532 P < 0.05), but silicon content did not have a significant correlation (r = 0.042 P > 0.05), indicating wax-enhanced potato resistance to R. solani. The correlation between soluble starch, soluble protein, soluble sugar and free amino acid and disease index were 0.476 (P < 0.05), 0.458 (P < 0.05), 0.300 (P > 0.05) and 0.219 (P > 0.05), respectively. This showed that lower levels of soluble starch and higher levels of soluble protein enhanced disease resistance, while soluble sugar and free amino acid had no significant effects on disease resistance.