Pests

Nematodes

Nematodes are microscopic roundworm endoparasites that feed on plant sap and cause significant yield losses. Varietal resistance is provided by genetic mechanisms that prevent pest reproduction and is assessed according to the International Seed Federation scale.

Mentioned in descriptions 13 637 varieties reference book.

Nematodes are microscopic roundworms ranging from 0.3 to 2 mm in size that act as obligate plant parasites. Most species penetrate root, stem, or bulb tissues, causing growth inhibition, wilting, and patchy crop development, with tissue damage often facilitating secondary infections.

Varietal resistance to nematodes is based on the plant's genetic apparatus, including specific R-genes that limit the feeding or reproduction of the pest. In some cases, protection is provided by a hypersensitive response, where local cell death occurs at the site of infection.

Protection efficacy is evaluated using International Seed Federation codes: HR denotes high resistance with limited parasite development under high inoculum pressure, while IR indicates intermediate resistance. The level of protection is race-specific and depends on the specific species and pathotype of the nematode.

Sources10

Breakdown by crop

Root-knot nematodes of tomato 1 711 Potato nematodes 1 231 Nematodes of sugar beet 287 Pepper Nematodes 154 Nematodes — Oilseed radish 143 Nematodes in white mustard 105 Nematodes — Tomato (Interspecific Hybrids) 79 Alfalfa nematodes 62 Barley nematodes 55 Root-knot nematodes of tomato 49 Soybean cyst nematode 35 Grapevine Nematodes 32 Plum nematodes 24 Peach nematodes 22 Rice nematodes 22 Nematodes in black oat 21 Nematodes of oats 20 Citrus Nematode 19 Nematodes — Prunus amygdalus x Prunus persica 16 Nematodes of White Clover 15 Nematodes in Prunus davidiana × Prunus persica hybrids 14 Nematodes — Solanum torvum Sw. 14 Nematodes — common wheat 14 Nematodes — hybrids between Citrus x aurantium L. x Citrus trifoliata L. 13

Found in these crops

Tomato 1 709 Potato 1 216 Sugar beet 288 Bell pepper 152 Oil radish 143 White mustard 105 hybrids between Solanum lycopersicum L. and S. habrochaites S. Knapp & D.M. Spooner 79 Alfalfa 62 Barley 53 Tomato 48 Soybean 33 Grapevine 32

Varieties that feature this in their description

Selection based on the description text, not official resistance ratings: such data is not available in registers. Mention indicates that the trait is discussed in the variety's sources; see the variety's profile for details on what is specifically stated.