VIEW ARTICLE

Etiology

Response of Tomatoes to Ozone, Sulfur Dioxide, and Infection by Pratylenchus penetrans. B. B. Shew, Graduate assistant, U.S. Department of Agriculture, Department of Plant Pathology, North Carolina State University, Raleigh 27650; R. A. Reinert(2), and K. R. Barker(3). (2)Plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, North Carolina University, Raleigh 27650; (3)Plant pathologist, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 72:822-826. Accepted for publication 8 September 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982.. DOI: 10.1094/Phyto-72-822.

Tomato plants (Lycopersicon esculentum ‘Walter’) were inoculated with initial population densities of Pratylenchus penetrans ranging 0–4,000 nematodes per pot and were repeatedly exposed for 3 hr to ozone (O₃) doses ranging 0.0–0.4 μl O₃/L of air (1 μl O₃/L of air = 1,960 μg O₃/m³ of air). In other experiments, tomato plants, uninoculated or inoculated with P. penetrans, were exposed (4 hr per exposure) 15 times to 0.2 μl O₃/L of air, or 0.2 μl SO₂/L (1 μl SO₂/L of air = 2,620 μg SO₂/m³ of air), or both, or were exposed (3 hr per exposure) to 0.2 μl O₃/L of air or 0.8 μl SO₂/L of air, or both. Exposures to charcoal-filtered air served as controls. Decreases in dry weights of plant parts excised from tomato plants exposed to 0.2 μl O₃ per liter of air added to the decrease in dry weight caused by exposure to sulfur dioxide (SO₂) at 0.2 μl/L of air adequately predicted the decrease in dry weight of tomato plants caused by exposure to 0.2 μl O₃ + 0.2 μl SO₂ per liter of air. When 0.2 μl O₃ and 0.8 μl SO₂ per liter of air were present in mixture, they acted antagonistically and caused less change in leaf and shoot dry weight than could be predicted by the main effects of O₃ or SO₂. The presence of P. penetrans attacking the roots enhanced the negative effects of O₃ + SO₂ on leaf growth (dry weight), but suppressed the inhibitory effects of O₃ + SO₂ on axillary shoot dry weight. Treatments containing 0.8 μl SO₂ per liter of air reduced tomato fruit weight, but the amount of reduction was antagonized by the presence of O₃.