Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Efeito nematicida de compostos orgânicos voláteis (COVs) sobre o nematóide parasita de planta Meloidogyne javanica

SCIENTIFICS NOTES

Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Efeito nematicida de compostos orgânicos voláteis (COVs) sobre o nematóide parasita de planta Meloidogyne javanica

Mauricio Batista Fialho; Rosana Bessi; Mário Massayuki Inomoto; Sérgio Florentino Pascholati^*

Departamento de Fitopatologia e Nematologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Caixa Postal 09, 13418-900, Piracicaba, SP, Brazil

ABSTRACT

Previous studies have demonstrated that volatile organic compounds (VOCs), produced by the yeast Saccharomyces cerevisiae, were able to inhibit the development of phytopathogenic fungi. In this context, the nematicidal potential of the synthetic mixture of VOCs, constituted of alcohols and esters, was evaluated for the control of the root-knot nematode Meloidogyne javanica, which causes losses to crops of high economic value. The fumigation of substrate containing second-stage juveniles with VOCs exhibited nematicidal effect higher than 30% for the lowest concentration tested (33.3 µL g^-1 substrate), whereas at 66.6 and 133.3 µL g^-1 substrate, the nematode mortality was 100%. The present results stimulate other studies on VOCs for nematode management.

Aditional Keywords: phytonematode, nematicide, fumigation, alternative control

RESUMO

Estudos anteriores demonstraram que compostos orgânicos voláteis (COVs), produzidos pela levedura Saccharomyces cerevisiae, são capazes de inibir o desenvolvimento de fungos fitopatogênicos. Neste contexto, foi avaliado o potencial nematicida da mistura sintética de COVs, constituída por alcoóis e ésteres, para o controle do nematóide das galhas Meloidogyne javanica, que causa perdas em culturas de alto valor econômico. A fumigação do substrato, contendo juvenis de segundo estádio, com COVs apresentou efeito nematicida superior a 30% na menor dosagem testada (33,3 µL g^-1 de substrato), enquanto que nas dosagens de 66,6 e 133,3 µL g^-1, a mortalidade atingiu 100%. Os resultados encorajam maiores estudos envolvendo COVs no manejo de nematóides.

Palavras-chave adicionais: fitonematóide, nematicida, fumigação, controle alternativo

The javanese root-knot nematode Meloidogyne javanica is a major plant pathogen widespread in the tropics. As the management of M. javanica by traditional methods is laborious and infested areas frequently become not viable for agricultural use, the development of new control methods is desirable.

In previous studies, VOCs produced by the yeast Saccharomyces cerevisiae, or their artificial mixtures, inhibited several phytopathogenic fungi (1, 2). The effect of VOCs on plant parasitic nematodes is scarcely studied. Thus, an in vitro assay was carried out in order to evaluate the effect of an artificial mixture of VOCs, identified from the yeast, on the survival of M. javanica juveniles.

The artificial mixture of VOCs was prepared by using standard chemicals (Sigma-Aldrich), based on the results of the analysis of gaseous atmosphere produced by S. cerevisiae (1). The analysis was carried out by Fialho et al. (1) by using gas chromatography with mass spectrometric detection (GC-MS). The concentration of each compound present in the mixture was based on its relative proportion (%), estimated by the area in relation to all other components of the mixture (Table 1). The population of M. javanica was maintained in soybean plants in a greenhouse. M. javanica egg masses were stained by immersing the roots in phloxine B solution (0.0015%) for 20 min. Then, the egg masses were hand-picked, transferred to hatching chambers and maintained at 30 °C (4). A suspension of second stage juveniles (J2) of the nematode was obtained after 24h and used as inoculum. Commercially available polystyrene plates (60 mL volume) divided in half by a wall were used for the assay. On one side of the plate, a total of 2.3 mL of the suspension containing 1,000 juveniles (J2) was added to 1.5 g of the substrate vermiculite. On the opposite side, different volumes of the artificial mixture of VOCs (50, 100 and 200 µL) were added to a cotton wool to obtain the concentrations of 33.3, 66.6 and 133.3 µL g^-1 substrate. Immediately after the addition of compounds, the plates were sealed and maintained at 27 °C in the dark. The control treatment consisted of plates containing the nematodes in the absence of VOCs. A total of 10 replicates were conducted for each treatment. After five days, the fumigated vermiculite was collected and transferred to a modified Baermann system (4), where it was maintained for five days at 30 °C. This procedure recovered only live nematodes after the treatment, which were counted using a stereoscope.

RESULTS AND DISCUSSION

An average of 40 and 27 nematodes were recovered, respectively, from the control and at the concentration of 33.3 µL g^-1. In contrast, at 66.6 and 133.3 µL g^-1 no nematodes were recovered. At the lowest concentration tested, the VOCs treatment resulted in the mortality of nearly one third of the nematodes when compared to control after 5 days of fumigation, while at higher concentrations all nematodes died (Figure 1).Previous work showed that the artificial mixture of VOCs or some of the components used alone were able to reduce the development of phytopathogenic fungi (2). The present assay proved that VOCs of S. cerevisiae also cause high mortality of plant parasitic nematodes.

There is limited research on the effect of microbial VOCs on plant-parasitic nematodes. The biofumigation with VOCs produced by the fungus Muscodor albus showed nematostatic and nematicidal effect on the nematodes Meloidogyne chitwood, M. hapla, Paratrichodorus allius and Pratylenchus penetrans in the roots and rhizosphere of beans, potatoes and pepper (5).

Grimme et al. (3) found that fumigation with volatiles produced by M. albus caused 74 and 100% mortality of M. incognita in the soil after 72 hours and 7 days of treatment, respectively. In in vitro assays, 5 ml mL^-1 of the artificial mixture of VOCs caused 100% mortality after 24h, while in in vivo assays, the concentration of 1.67 ml per cm³ of sand resulted in fewer galls on tomato roots. The formulation described in those experiments contained compounds such as 3-methyl-1-butanol, 3-methyl-1-butanol acetate and some esters of propanoic acid, whereas in the present work the main compounds were ethanol, 3-methyl-1-butanol and 2-methyl-1-butanol. The last two compounds were responsible for most antimicrobial activity against phytopathogenic fungi (1, 2). However, the specific compounds responsible for the mortality of the plant-parasitic nematodes have not been identified yet.

The present information stimulates further studies to evaluate the potential of these compounds in the control of nematodes and open perspectives for a new alternative control method, as the soil fumigation with methyl bromide is no longer available due to high toxicity and damage to the ozone layer.

ACKNOWLEDGMENTS

This research was supported by CAPES and CNPq.

Data de chegada: 17/05/2011

Aceito para publicação em: 02/01/2012

• 1. Fialho, M.B. Mecanismos de ação de compostos orgânicos voláteis antimicrobianos produzidos por Saccharomyces cerevisiae sobre o desenvolvimento de Guignardia citricarpa, agente causal da pinta preta dos citros 2008. 120p. Tese (Doutorado em Microbiologia Agrícola) - Esalq/USP, Piracicaba.
• 2. Fialho M.B.; Toffano L.; Pedroso M.P.; Augusto F.; Pascholati S.F. Volatile organic compounds produced by Saccharomyces cerevisiae inhibit the in vitro development of Guignardia citricarpa, the causal agent of citrus black spot. World Journal of Microbiology and Biotechnology, Amsterdam, v. 26, p. 925-932, 2010.
• 3. Grimme, E.; Zidack, N.K.; Sikora, R.A.; Strobel, G.A.; Jacobsen, B.J. Comparison of Muscodor albus volatiles with a biorational mixture for control of seedling diseases of sugar beet and root-knot nematode on tomato. Plant Disease, St. Paul, v. 91, p. 220-225, 2007.
• 4. Hooper, D.J. Extration of free-living stages from soil. In: Southey, J.F. Laboratory methods for work with plant and soil nematodes London: Her Majesty´s Stationery Office, 1986. p. 5-30.
• 5. Riga, E.; Lacey, L.A.; Guerra, N. Muscodor albus, a potential biocontrol agent against plant-parasitic nematodes of economically important vegetable crops in Washington State, USA. Biological Control, Orlando, v. 45, p. 380-385, 2008.

Publication Dates

• Publication in this collection
  23 July 2012
• Date of issue
  June 2012

History

• Received
  17 May 2011
• Accepted
  02 Jan 2012