AMSEED American Seed Intelligence Platform

Root-Knot Nematode

Meloidogyne spp. · nematode

Issue type
pest
Seedborne
No
Resistance code
N
Affects
Tomato, Cucumber, Watermelon

Symptoms

Stunted, wilt-prone plants that fail to respond to water and fertilizer; roots carry the diagnostic galls, swollen knots where juveniles feed. Damage concentrates in sandy soils and warm climates.

Management

The Mi gene (code N) makes resistant tomato hybrids the standard defense, with the caveat that Mi-mediated resistance weakens at sustained soil temperatures above ~82°F. Rotation to non-hosts like grasses and marigold cover-cropping reduce populations; heirlooms in infested sandy ground generally need grafting or containers.

Varieties with documented resistance

VarietyLevelCodeDaysBreeding
Better Boy resistant N 70-75 F1 hybrid
Celebrity resistant N 70-72 F1 hybrid
Big Beef resistant N 70-73 F1 hybrid
Mountain Merit resistant N 73-77 F1 hybrid
Amelia resistant N 75-80 F1 hybrid
Lemon Boy resistant N 72-75 F1 hybrid
Mountain Fresh Plus resistant N 75-78 F1 hybrid
Damsel resistant N 70-75 F1 hybrid
Viva Italia resistant N 72-80 F1 hybrid
Super Marzano resistant N 70-80 F1 hybrid
Sweet Chelsea resistant N 65-70 F1 hybrid
Bush Early Girl resistant N 54-63 F1 hybrid
Better Bush resistant N 68-72 F1 hybrid
Bush Goliath resistant N 65-70 F1 hybrid
Beefmaster resistant N 80-85 F1 hybrid
SuperSteak resistant N 80-85 F1 hybrid
Park's Whopper resistant N 65-70 F1 hybrid
Champion resistant N 62-70 F1 hybrid
Crista resistant N 72-78 F1 hybrid
Red Snapper resistant N 70-75 F1 hybrid

Sources & References

Evidence: 2 sources, all independent references.

  1. Vegetable MD Online · Cornell University, Plant Pathology, University or Government
  2. Tomato Production and Cultivar Guides · University of Florida IFAS Extension, University or Government