Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/1999
Publication Date: N/A
Interpretive Summary: Nematode parasitization of tomato plants diverts new growth from shoots to roots. The environment surrounding the host plant, both above and below ground, can affect development of root-knot nematodes. In previous controlled-environment studies with constant temperature and photosynthetic light ending each day with high or low far-red to red photon ratios (FR/R), ,tomato seedlings that received the higher FR/R developed larger shoots, higher shoot to root weight ratios, and fewer nematodes per plant. Field studies of nematode-inoculated tomato plants grown over red versus black mulches in trickle-irrigated field plots showed that the earlier shoot growth over the FR-reflecting red mulch resulted in greater early crop yields, with less yield loss to nematode infection of roots. In the present study, tomato seedlings were grown for 50 days in insulated boxes of soil inoculated with different numbers of root-knot nematode eggs. The boxes were covered with white, red, or black surfaces in a glasshouse. Al received the same incoming light, and soil temperatures were similar in all boxes. The white surfaces reflected the most photosynthetic light and low FR/R, red reflected less photosynthetic light and higher FR/R than white, and black reflected less than five percent of any color. Seedlings over white developed more branches, larger leaf areas, and they had more massive shoots and roots. At 50 days, plants grown over white and red had similar numbers of juvenile (J2) nematodes per plant, but those over red had more per gram of root weight. We conclude that quantity and spectrum of light reflected to seedlings from different colors on the soil surface can affect nematode reproduction when soil temperature does not differ below the different colors.
Technical Abstract: The effect of different colored polyethylene mulches on quantity and spectra of reflected light, plant morphology and root-knot disease was studied in tomato (Lycopersicon esculentum) grown in simulated planting beds. Tomato plants were inoculated with Meloidogyne incognita at initial populations of 0, 1000, 10,000 or 50,000 eggs per plant, and grown in a greenhouse for 50 days over white, red or black polyethylene mulch. Soil temperature was maintained constant among the mulch treatments by placing an insulation barrier between the colored mulch and the soil surface. Soil temperatures varied <0.5 C between soil chambers at solar noon. White reflected more total light and a lower far-red to red ratio than red mulch, whereas black reflected less than 5% of any color. Plants over white developed more branches, heavier shoots and roots, and greater leaf area than plants grown over red or black surfaces. Roots of plants grown over white and red contained similar numbers of second-stage juveniles (J2) per plant, but the number of J2 per gram of dry root wt was greater over red. The root-gall index was lower for plants grown over white mulch than for plants grown over red mulch. The light environment of the shoots during the first 50 days of growth affected the nematode population(P<0.05).