Host Status of Indigenous Leafy Vegetable and Weed Species to Root-Knot Nematodes

Plant-parasitic nematodes are soilborne pathogens that have a wide host range, infecting agricultural and horticultural crops as well as weed plant species worldwide. Sixteen indigenous leafy vegetable species were screened for host suitability to Meloidogyne javanica and M. incognita race 2, respectively, in two independent greenhouse trials. Two weed species, namely Hibiscus trionum and Tagetes minuta were included in each trial as the positive and negative standards, respectively. Each four-leave stage seedling was inoculated with 5,000 +/- 520 root-knot nematode eggs and second-stage juveniles (J2) 14 days after planting. Nematode evaluations were done 56 days later and included the following parameters viz., number of egg masses/root system and number of eggs and J2/root system. In addition E. L. F. indices and Rf values were calculated as well as the percentage resistance expressed by a given indigenous vegetable species. Substantial variation existed between the various indigenous vegetable species with regard to all nematode parameters investigated. Three indigenous leafy vegetables species maintained higher M. javanica eggs and J2/root system than the susceptible standard H. trionum. In addition, five of the sixteen indigenous leafy vegetable species had Rf values higher than 1 for M. javanica and eight for M. incognita, indicating susceptibility to the respective root-knot nematode species. However, twelve of these indigenous leafy vegetable species maintained Rf values lower than 1 for M. javanica, while eight showed the same tendency for M. incognita race 2. Results obtained during this study showed that indigenous vegetables are fairly susceptible to populations of the two root-knot nematode species used in this study.