"RESISTANT" VARIETIES:

DEFINITIONS

EXAMPLES

From: McKenry, M.V. and P. A. Roberts. 1985. Phytonematology Study Guide. University of California, Division of Agriculture and Natural Resources. Publication Number 4045.

Within nematology, the word resistance is used differently in different situations. The definitions provided here are from the University of California Phytonematology Study Guide. They are not agreed upon by all nematologists but are those that will be used in our discussion.

For example, root knot nematodes are not able to reproduce on nematode resistant tomatoes. However, alfalfa which is sold as nematode resistant may support substantial populations of nematodes and should not be used as a means to try to reduce nematode numbers in a crop rotation program. By these definitions, nematode resistant alfalfa would be a susceptible but tolerant host. When dealing with resistant varieties, one should always ask three questions: (1) which nematodes is the variety resistant to, (2) will nematodes damage the variety, and (3) will nematodes reproduce on the variety.

Although resistant varieties provide excellent protection, do not plant them year after year in the same field. Root knot nematode populations have the potential to overcome host plant resistance when exposed repeatedly to varieties with the same genetic background.

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