Ja. Thies et al., EVALUATION OF OKRA ACCESSIONS WITH REPORTED RESISTANCE TO ROOT-KNOT NEMATODES FOR REACTION TO SOUTHERN ROOT-KNOT NEMATODE, HortScience, 33(2), 1998, pp. 321-322
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.