Submitted to: Nematropica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2016
Publication Date: 6/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62741
Citation: Meyer, S.L., Chauhan, K.R., Macdonald, M.H. 2016. Evaluation of roselle (Hibiscus sabdariffa) leaf and pomegranate (Punica granatum) fruit rind for activity against Meloidogyne incognita. Nematropica. 46(1):85-96.
Interpretive Summary: Root-knot nematodes are economically important plant parasites that attack most crop plants. Fewer synthetic nematicides are available for managing these nematodes, so new methods and products are needed to fill this gap. Plant products are being investigated for use as nematode management agents. The skin and underlying peel of pomegranate fruits are a waste byproduct of the pomegranate juice industry. Therefore, these parts of the pomegranate fruits, and leaves of roselle, a fiber, food and medicinal plant, were dried and ground to a powder. In laboratory tests, extracts made from these powders prevented root-knot nematode egg hatch and killed juvenile nematodes. In the greenhouse, the powdered pomegranate was applied to soil. Suppression of root gall production on cucumber roots varied between trials. These studies showed that compounds in pomegranate fruit skin/peels and in roselle leaves are active against the root-knot nematode. The results will be used by researchers developing agricultural applications of these products.
Technical Abstract: Pomegranate (Punica granatum) fruit and roselle (Hibiscus sabdariffa) leaves have been used in traditional medicine, including as anthelmintics. Methanolic extracts from these plants were investigated for activity against the southern root-knot nematode (RKN) Meloidogyne incognita. Dried, ground powders were prepared from pomegranate fruit (skin/peel) and from roselle leaves. In in vitro assays, methanolic extracts from both powders inhibited egg hatch and viability of second-stage juveniles (J2), although some of the effect on J2 was nematostatic, depending on the extract concentration. The pomegranate extract was effective at low concentrations (0.45% to 1.8%), reducing egg hatch up to 94%, and killing more than 30% of the J2. Higher concentrations (4.5% and greater) of roselle extract were needed for this effect, with 100% loss of J2 viability in concentrations of 22.5% and 45.0%. Increasing extract pH did not affect activity. Pomegranate powder was tested as a soil amendment in greenhouse trials, and was phytotoxic to cucumber seedlings at application rates of 5.0% and 10.0% (w/w soil). Shoot heights and fresh weights were not significantly reduced at 0.25% and 0.5% powder, but there was a trend toward some height and weight reduction. Root fresh weights were not reduced at those concentrations. The number of galls/g fresh root weight was suppressed in 1.0% powder in one of two trials, but not in 0.25% or 0.5%. Amendment with powder resulted in rapid growth of Rhizopus sp. and Aspergillus sp. on the soil, which increased with application rate. Extracts from pomegranate fruit (skin/peel) and roselle leaves suppressed RKN populations, indicating that these plant-derived products are potential candidates for future studies of nematode-antagonistic compounds.