New Sources of Resistance to Root-Knot Nematodes among Primitive Cottons
1983
Shepherd, Raymond L.
Presently, Auburn 634 RNR and related cottons are the only germplasm in upland cotton (Gossypium hirsutum L.) with extremely high resistance to root-knot nematodes (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood]. Genetic vulnerability could result from using only this one source for breeding resistant cultivars. The purpose of this study was to evaluate primitive race stocks of G. hirsutum to identify new, genetically diverse sources of RKN resistance, and to compare the new sources with those now in upland cottons. Of 471 primitive race stocks evaluated, 18 (3.8%) were resistant. None were as resistant as Auburn 634 RNR, although several approached it. Number of eggs produced on the eight race stocks having the highest resistance ranged from 2.8 to 5.5 times fewer than were used initially to inoculate them. Resistance was widely distributed among stocks of different races (originating from the same and different geographic areas), indicating the potential diversity of the resistant germplasm. Evidence is presented that RKN resistance should be relatively stable over time and should control RKN across many geographic regions of the world.
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