Effects of Pyrenochaeta lycopersici infection on nutrient uptake by tomato plants

The growth of young tomato plants in nutrient solution or in soil and infected with Pyrenochaeta lycopersici Schneider & Gerlach, the cause of tomato brown root rot, was decreased relative to that of uninfected plants. The roots of plants grown in nutrient solution and infected with a mycelial mat of the pathogen contained lower concentrations of potassium and higher concentrations of calcium than roots of uninfected plants. These changes occurred largely in the visibly affected tissue, as opposed to the root system as a whole. The concentrations of magnesium, total nitrogen and phosphorus in the roots of infected plants were not significantly different from those of control plants. Magnesium, nitrogen and phosphorus concentrations in the tops of infected plants were also not significantly different from those of healthy plants, but no consistent changes were found in the concentrations of calcium and potassium. Young tomato plants grown in soil infested with P. lycopersici contained lower concentrations of phosphorus and potassium in the tops than plants grown in sterilized soil. It was not possible to separate intact damaged root systems of infected plants from soil. The changes in composition found in infected plants are discussed in relation to possible methods of manipulating the nutrition of the plant to offset the effects of the disease on crop yield.