BIOMASS PARTITIONING AND ROOT-KNOT NEMATODE DEVELOPMENT IN TOMATO PLANTS UNDER END-OF-DAY RED OR FAR-RED LIGHT

The ratio of far-red to red light received by a growing plant alters the photoequilibrium of the phytochrome system and regulates partitioning of photosynthate among stems, leaves, and roots. This study was conducted in a controlled environment to determine whether red or far-red light received by tomato (Lycopersicon esculentum Mill. cv. Rutgers) shoots can affect activity of root-knot nematode, Meloidogyne incognita (Kofoid and White). Nematode-inoculated and noninoculated plants received 5 min of red (a low far-red to red ratio) or 5 min of far-red (a high ratio) light at the end of the daily 12-h photosynthetic period for 32 d consecutively, after which plant parameters and nematode presence were measured. The red or far-red light treatments altered plant growth patterns and the reproduction of M. incognita. Plants that received the far-red light treatment were taller, heavier, and had a greater leaf area than red light-treated plants. Also, the far-red light-treated plants were lighter green in color, developed longer internodes, had greater leaf mass and a higher shoot/root biomass ratio than plants treated with red light. Meloidogyne incognita-inoculated plants that received the far-red light had fewer eggs and fewer egg masses than plants that received red light. Crop production procedures such as use of plant residues, colored mulches, and other practices that affect the ratio of far-red relative to red light in growing plant canopies might influence nematode parasitism of tomato.