Phytophthora erythroseptica Pethyb. is a devastating fungal pathogen of potato (Solanum tuberosum). The pathogen causes a disease known as pink rot. Pink rot results in necrosis and decay of tubers; and is responsible for major losses pre and post harvest. Attributes of the disease are progressing toward epidemic proportions. To help prevent such dramatic outbreaks of the disease, understanding the factors associated with incidence will provide opportunities to control the pathogen. A link between pH and disease severity has been observed. We studied the effects of pH and Ca to determine their influence on disease development. Low pH and Ca deficiencies are often inter-related factors that can be causal of one another. The pH effect could be due to either H+ or Ca ions. To separate their interactive effects we tested each variable individually using hydroponics and nutrient solutions. We assessed disease severity by assigning an Infection Coefficient (IC) to each root and stolon samples. The IC values were determined by quantifying DNA and then creating a ratio of host to pathogen DNA within root tissue. The DNA was measured by quantitative RT PCR. Statistical analysis showed significance in greater pathogen presence at more acidic pH and lower levels of available Ca. Significant reductions in IC values were observed when pH was elevated above pH 7. There was a notable increase in colonizing pathogen DNA at pH 5. Ca was significant, and as levels of soluble Ca increased the degree of disease severity became smaller. The effect of Ca was found not to be dependent upon pH. These results suggest immediate and cost effective applied management strategies to reduce incidence and disease severity outbreaks. Amending the soil with lime to increase soil pH and Ca content is one such potential method.



College and Department

Life Sciences; Plant and Wildlife Sciences



Date Submitted


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pink rot, Phytophthora erythroseptica, pH, Calicium, potato, solanum tuberosum