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Project description

Weed Resistant Tomatoes. (98CC008)
Program UC IPM competitive research grants program
M. McGiffen, Botany and Plant Sciences, UC Riverside
Host/habitat Tomatoes
Pest Black Nightshade; Velvetleaf Abutilon theophrasti
Disciplines Plant Sciences, Weed Science
Cultural Controls
Start year (duration)  1998 (Two Years)
Objectives Quantify light interpretation, growth, and other ecophysiological processes related to varietal tolerance of weeds.

Derive INTERCOM model parameters for H8892, Boss 3155, and 145B-7879 tomato varieties and black nightshade. (PI changed target weed to velvetleaf.)

Validate model for processing tomato and black nightshade.

Use sensitivity analysis to evaluate characteristics that confer varietal tolerance.

Resistance to pathogens, insects, and nematodes has long been an important pest management tool. However, no crop varieties have been bred for resistance to weeds. We tested four processing tomato varieties for their ability to resist yield loss from interference with velvetleaf. Velvetleaf was selected as the test weed because it has increased in prevalence in California, but little is known of its competitive ability with vegetable crops. Five velvetleaf plants m-1 of row reduced marketable tomato yield by 8-64% in 1998 and by 58-80% in 1999. Fifty velvetleaf plants m-1 caused yield losses of 54 to 87% in 1998 and 97 to 99% in 1999. Although velvetleaf did not significantly affect tomato height, it severely reduced tomato canopy width and leaf area starting with the early stages of growth. But velvetleaf also competes vigorously with itself, decreasing dramatically in size as its own density increases.

The tomato varieties differed in their ability to resist yield loss from velvetleaf interference. H8892 was the most tolerant variety and H9961 the least tolerant. The ability to compete with velvetleaf was directly related to the rate at which each variety increased leaf area. These experiments provide the parameters for a simulation model that will assess competitive strategies. For example, model parameters for early and late season leaf area and growth can be varied to test whether a tomato variety with rapid late-season growth will be more effective at outcompeting velvetleaf than a variety that puts more resources into early season growth.

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