EVALUATION OF OKRA ACCESSIONS WITH REPORTED RESISTANCE TO ROOT-KNOT NEMATODES FOR REACTION TO SOUTHERN ROOT-KNOT NEMATODE

Forty-seven of the 53 plant introductions (PI) in the U.S. Plant Germp lasm System okra [Abelmoschus esculentus (L.) Moench] collection with reported resistance to root-knot nematodes [Meloidogyne incognita (Kof oid and White) Chitwood or unidentified Meloidogyne spp.] were evaluat ed in replicated greenhouse tests for reaction to the southern root-kn ot nematode (M. incognita). (Four of the 53 PI were unavailable and tw o accessions failed to germinate.) Preliminary evaluations identified a serious problem in evaluating this subset of okra germplasm for resi stance to root-knot nematodes, The seed coats of most of the accession s were hard, and this trait delayed germination, which caused many of the seedlings to escape infection when the seeds were inoculated at pl anting with M. incognita eggs, A seed disinfection, scarification, and germination procedure was developed to ensure uniform seedling emerge nce. Except for two PI that failed to germinate, all available okra ac cessions with reported resistance were evaluated using these procedure s. All tested accessions were susceptible to M. incognita race 3. Base d on these results, we conclude that none of the accessions in the okr a PI collection with reported resistance to root-knot nematodes is use ful as M. incognita-resistant parental material in okra breeding progr ams.