ARS | Publication request: SUSCEPTIBILITY OF OKRA ACCESSIONS PREVIOUSLY REPORTED RESISTANT TO MELOIDOGYNE INCOGNITA

Submitted to: Nematropica
Publication Type: Abstract Only
Publication Acceptance Date: July 7, 1996
Publication Date: N/A

Technical Abstract: Forty-five okra accessions previously reported as resistant to M. incognita race 3, or to unidentified species or races, were evaluated in greenhouse tests for resistance to M. incognita race 3. Seed coats of most accessions were hard and seed germination was erratic. Therefore, seeds were germinated before planting to ensure even seedling emergence. Three seeds per entry were planted on 12-cm-centers in greenhouse benches containing a steam-sterilized sand and soil mixture. Each seed was inoculated with 1500 eggs of M. incognita race 3. The experimental design was a randomized complete block design with 6 replicates. Greenhouse temperatures were maintained at 27 +/- 7C. Four weeks later, roots were scored for galling severity and egg mass production using a 1 to 5 scale (1 = 0 to 3% of root system galled or covered with egg masses; 5 = 81 to 100% of root system affected), and eggs were extracted from roots. Gall and egg gmass indices ranged from 4.4 to 5 and 3.6 to 4.3, respectively. Numbers o eggs/g fresh root ranged from 76,000 to 119,000. The experiment was repeated with similar results. We concluded that all okra accessions tested were susceptible to our isolate of M. incognita race 3. Differences in our results and those previously reported may be attributed to: (1) differences in nematode isolates; (2) delayed seed germination that may have allowed okra roots to escape nematode infection.