International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

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NEMATICIDAL ACTIVITY OF AQUEOUS EXTRACTS FROM RUE (RUTA GRAVEOLENS L.)
T. D’Addabbo and N. Sasanelli
Istituto per la Protezione delle Piante- Cnr, Sezione di Bari
Via G. Amendola 165/A – 70126 Bari. Italy
E-mail: nematd12@area.ba.cnr.it
Summary. The effect of leaf and root aqueous crude extracts and of root leachates of R. graveolens on the root-knot
nematodes Meloidogine arenaria, M. hapla, M. incognita and M. javanica, and on the beet cyst nematode Heterodera
schachtii was investigated in a in vitro experiment. Aqueous extracts were prepared by soaking green leaves or roots in
distilled water and root leachates were collected by drenching the rue cultivated soil with excess tap water. Egg masses
of each Meloidogyne species and cysts of H. schachtii were incubated in the test solutions over a four weeks period.
Immersion in rue extracts significantly suppressed juvenile emergence from the egg masses of all the four
Meloidogyne species and from cysts of H. schachtii. Leaf extract was always more effective than root extract for
Meloidogyne species, whereas no difference resulted in H. schachtii. No synergic effect derived from the combination
of the two extracts. No significant emergence reduction resulted from the immersion in rue root leachates for any of the
tested nematode species.
INTRODUCTION
Several plants are reported to minimize nematode damage in vegetable and field crops by producing nematicidal
(killing) and nematistatic (suppressive) organic compounds. These natural compounds can be released from the roots of
living plants or by plant tissues incorporated into the soil as a green manure (Grainge and Ahmed, 1988).
The biocidal effect of extracts from rue (Ruta graveolens L.) was previously reported on insects, fungi and weeds
(Aliotta et al., 1994; 1999; Oliva et al., 1999), but few information is available on the effect on phytoparasitic
nematodes. Therefore an experiment was undertaken to investigate the in vitro effect of leaf and root aqueous extracts
and of root leachates of R. graveolens on four different species of root-knot nematodes, Meloidogine arenaria (Neal)
Chitw., M. hapla Chitw., M. incognita (Kofoid et White) Chitw.and M. javanica (Treub) Chitw. and on the beet cyst
nematode Heterodera schachtii Schmidt.
MATERIALS AND METHODS
Aqueous extracts of rue were prepared by soaking 100 g green leaves or roots, or 50 g when in combination, in 400 ml
distilled water for 24 hrs. Tissues were then macerated in a blender and the suspension filtered through filter paper.
Root leachates were collected from three month old plants, cultivated in fifteen 2,500 cm 3 clay pots, by drenching the
soil with excess tap water. The leachates were then centrifuged at 1,300 g for 30 min, stored in plastic bottles, and kept
in a freezer until required. In the experiment on H. schachtii each plant extract or root leachate was adjusted to 3 mM
adding an equal volume of 6 mM of zinc sulphate (Clarke and Shepherd, 1966).
The four Meloidogyne populations were reared on tomato cv. Roma in a glasshouse at 20-25 °C, whereas H. schachtii
was collected from an infested field at Avezzano (L’Aquila). Batches of twenty egg masses (averaging 20,000 eggs per
mass) of each Meloidogyne species or 100 cysts of H. schachtii (123 egg/cyst) were placed on 2 cm diam sieves (215
µm aperture) and each sieve in a 3.5 cm diam Petri dish. Three ml of each test solution, were then added to four batches
of egg masses or cysts. Distilled water (for Meloidogyne species) or 3 mM zinc sulphate solution (for H. schachtii) and
a 5 µg/ml aqueous solution of fenamiphos were used as controls.
The dishes were arranged in a complete randomized block design with four replicates of each treatment: egg masses of
Meloidogyne species were incubated at 25 °C, whereas the cysts of H. schachtii were mantained at 20 °C. Emerging
juveniles were removed and counted at weekly intervals, renewing the hatching solutions at the same time, over a nine
or ten weeks period, respectively for Meloidogyne species and H. schachtii. Egg masses and cysts were removed from
the test solutions after the first four weeks and the incubation continued in distilled water or, for cysts of H. schachtii, in
the zinc sulphate aqueous solution.
At the end of the experiment the egg masses were immersed in a 1% sodium hypochlorite aqueous solution (Hussey and
Barker, 1973), whereas the cysts were crushed, according to Seinhorst and Den Ouden (1966). Unhatched eggs from
egg masses and cysts were then counted. Numbers of juveniles emerging weekly were expressed as cumulative percent
of the total initial population. Data were statistically analysed and compared by LSD’s test.
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