Abstract
The nematicidal effect of three marine algal, Ulva fasciata Delile (UF) (green algae), Corallina mediterranea, Corallina officinalis (red algae), extracts on egg hatching and second-stage juveniles (J2) mortality of root-knot nematode (Meloidogyne incognita) in vitro compared to the nematicide activity of Oxamyl 24% SL (5 ml/l) was investigated. Results revealed that all treatments at the applied concentrations suppressed the egg hatching in 3 days. In details, the algal strain Ulva fasciata Delile extract showed the highest activity in decreasing the eggs hatchability after 3 days with 87%. Consequently, all treatments significantly increased the mortality of J2 larvae after 12, 24, and 48 h compared to the control treated with distilled water. Under greenhouse conditions, all treatments in inoculated soils cultivated with tomato plants had reduced numbers of galls, egg-masses/plant, and the number of J2/250 g than the non-inoculated soil. The algal extract and the Oxamyl 24% SL (5 ml/l) increased the length and fresh weight of plant shoots and roots than the untreated. However, there were no differences in shoots and roots fresh weights and their lengths in the plant treated with Oxamyl 24% SL (5 ml/l) or the extracts of U. fasciata and Corallina officinalis. These results were closely similar to control. Both of peroxidase and polyphenol enzymes activity for the control plants remained relatively stable, while the activity of the two enzymes in the plant inoculated with the nematode decreased during 2 to 18 day post inoculation (dpi). These activities increased in inoculated plants treated with C. officinalis, C. mediterranea, and U. fasciata extracts and the other plants treated with Oxamyl 24% SL (5 ml/l). The maximum activity of the three enzymes was recorded at 5 dpi after treatment with U. fasciata.
Highlights
Management of soil-borne plant pathogens, including parasitic nematodes, is one of the single greatest challenges facing modern agriculture worldwide
Chemical nematicide are losing their popularity among farmers for protecting their crops from nematode infestations because of their harmful effects and environmental pollution that led to an urgent need for safe and more effective options
The nematicidal effect of the used concentrations of C. mediterranea, C. officinalis, and U. fasciata extracts in addition to the nematicide, Oxamyl 24% SL (5 ml/l), on the egg hatching and Second-stage juveniles (J2) mortality of M. incognita was investigated and the results revealed that, on the third day of treatment, 21.6% of eggs hatched and increased to 52.6% on the seventh day in the control group
Summary
Management of soil-borne plant pathogens, including parasitic nematodes, is one of the single greatest challenges facing modern agriculture worldwide. The root-knot nematodes, Meloidogyne Göldi, 1892 (Rhabditida: Meloidogynidae) belongs to the most economically important plant that causes serious damage to most agricultural crops worldwide The use of chemical nematicide is one of the primary means of control for root-knot nematodes (Baidoo et al 2017). The use of marine algae as control agent against plant-parasitic nematodes has been studied by many researchers (Youssef and Ali 1998). Wu et al (1997) reported the role of betaines in alkaline extracts of the marine brown algae Ascophyllum nodosum (Linnaeus) Le Jolis in suppression of the fecundity of tomato-knot nematodes Meloidogyne javanica and Meloidogyne incognita. Ibrahim et al (2007) stated that treating sunflower plants with marine algae, Botryocladia cabillaceae caused reduction in root galls and egg masses of M. incognita as well as increased growth parameters. Khan et al (2015) evaluated in vitro the nematicidal activity of 32 seaweeds on M. javanica egg hatching and larval mortality and recorded that Sargasssum tenerrimum, Padina tetrastromatica, and Melano thamnusafa qhusainii gave maximum egg hatching (96%) and larval mortality (99%) and (100%), in water and methanol extract at 10% concentration after 72-h exposure time respectively
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