Breeding Potatoes for Columbia Root-Knot Nematode Resistance

April 26, 2024October 17, 2025

How is nematode resistance measured?

Nematode reproduction on plant host:
1. Inoculate each plant with known quantity of nematodes
2. Culture inoculated test plants for >60 days (2 – 3 generations)
3. Extract nematodes from soil and calculate abundance using microscope
4. Calculate reproductive factor (RF)

RF = Final nematode count/number of nematodes at start of trial
• RF > 1 is a good host (susceptible)
• RF < 1 is a poor host (tolerant)
• RF < 0.1 is a non-host (resistant)

Evaluating nematode reproduction on host plant

Field screen for nematode damage:
Plant clones in a nematode infested field and evaluate symptomology

Root galling, embedded egg masses, and mild to severe damage from Columbia root-knot nematode

Are there any known sources of genetic resistance to Columbia root-knot nematode (Meloidogyne chitwoodi)?
There are no cultivated potato varieties that exhibit resistance to Columbia root-knot nematode.

No cultivated potato varieties have resistance to Columbia root-knot nematode

Screens of wild potato relative species have identified the following species that are non-hosts:
• Solanum bulbocastanum
• Solanum hougasii
• Solanum fendleri (stoloniferum)

Wild potato relative species that are non-hosts for nematodes

Introgression of resistance:
1. Resistance from S. bulbocastanum was introgressed into S. tuberosum background through somatic hybridization
2. Resistances is inherited dominantly across multiple genetics backgrounds

Introgression of Columbia root-knot nematode resistance into potato varieties

Our most advanced resistant clones do not meet industry standards:
• PA99N82-4 has low specific gravity
• PA99N82-4 is not oblong enough for French fry production