EFFECT OF SOME PLANT EXTRACTS ON ROOT KNOT NEMATODES

Abstract

Root-knot nematodes, Meloidogyne spp are responsible for a great economic losses in many agriculture crops and considered the most difficult pest to control. In the present investigation, five plant materials (root of Saponaria officinalis, seeds of Peganum harmala and Trigonella foenum-gracum, leaves of Artemisia annua and Nerium oleander) were used to evaluate the nematicidal potency of their extracts. Powder of plants were stepwise extracted with hexane, ethyl acetate, methanol and distilled water. The results of a primary in vitro experiment clearly demonstrated high significant nematicidal potencies of aqueous plant fractions and methanolic fraction of Trigonella foenum-gracum compared to non-treated control. Also, egg hatchability was decline due to treatments of nematode eggs with the aqueous plant fractions or the mixture. The concentration of 20 mg/ml of the mixture of aqueous fractions and aqueous fractions of Saponaria officinalis, Artemisia annua, Nerium oleander, and Trigonella foenum-gracum can completely prevent nematode egg hatching. The effect of these aqueous extracts on the nematode acetylcholinesterase (AChE) was estimated by exposure of second stage juveniles (larvae) to 20 mg/ml of aqueous fractions of all plant materials, a mixture of all aqueous fractions and methanol fraction of Trigonella foenum-gracum and compared to the well known nematocide oxamyl. Acetylcholinesterase (AChE) was inhibited due to incubation with oxamyl as well as all aqueous fractions except Peganum harmala which lead to higher activity of AChE than control. The maximum inhibition of AChE was recorded in nematode larvae treated with the aqueous fraction of Nerium oleander. To evaluate the ability of these plant extract to induce plant resistance against root-knot nematodes, a greenhouse experiment was carried out by treatment of nematode-infected cucumber seedlings with aqueous fractions of all plant materials, their mixture, and methanol fraction of Trigonella foenum-gracum. The results showed that all treatments significantly reduced the number of galls, egg masses, and female, hatched nematode of M. inconita in infected cucumber plants as compared to infected control.