Phytophthora erythroseptica (Pink Rot) Development in Russet Norkotah Potato Grown in Buffered Hydroponic Solutions II. pH Effects

Pink rot caused by the pathogen Phytophthora erythroseptica Pethyb. causes severe pre- and post-harvest losses in potato. Severe losses of potato from pink rot infection suggest the need for better information on cultural factors associated with disease development. Soil pH has been regarded as a strong influence on disease development as observed by previous studies and by commercial potato growers. A hydroponic growth system was established to study the effects of pH on P. erythroseptica infection and colonization in Russet Norkotah potato roots. Russet Norkotah plantlets were grown in hydroponic nutrient solutions buffered at pH 5, 6, 7, and 8 and evaluated for infection by means of quantitative Real Time PCR. Acidic pH solutions produced a higher proportion of pathogen to host DNA in root tissue, indicating increased infection and colonization at low pH. Thus, pH has a unique and significant influence on the levels of infection from P. erythroseptica and that commercially grown potatoes would likely develop reduced tuber rot if grown in soils with pH at or above 7.