Phytophthora Root Rot and Irrigation Schedule Influence Growth and Phenology of Processing Tomatoes

Abstract

Abstract Processing tomatoes (Lycopersicon esculentum Mill.) grown in field plots with soil infested or not infested with Phytophthora parasitica Dastur. were furrow-irrigated for 4 to 8 hr every 14 days (normal) or 28 days (less frequent) or with alternating 4- to 8-hr and 24-hr irrigations every 14 days (prolonged). Disease developed more rapidly and symptom severity was significantly greater on shoots and roots of plants that received prolonged irrigations. Disease symptoms on roots progressed more rapidly and were observed earlier than those on shoots in plants given prolonged or normal irrigation. Severe disease during early vegetative and reproductive growth caused significant reductions in total plant, leaf, and fruit dry matter and in the numbers of flowers and fruit in plants receiving either prolonged or normal irrigation. Diseased plants given prolonged irrigation also partitioned less total dry matter into leaves and fruit and more into stems than noninoculated plants. Less frequent irrigation of infested plots caused a delay in disease onset and reduced the impact of disease on numbers of flowers, fruit, and dry matter accumulation. Phytophthora-induced water stress during critical stages of crop development apparently can have major impacts on plant growth, phenology, and yield in processing tomato.