Rev 07/02/2024
Tylenchida Tylenchina Tylenchoidea Meloidogynidae Meloidogyninae
Meloidogyne exigua Goeldi, 1887
Meloidogyne exigua was the first root-knot species described under this genus name. It was described by Goeldi in 1887 having first been reported by Jobert in 1878 on coffee in Brazil.
Some history....(adapted from an article by Luiz Carlos Ferraz in Nematology Newsletter 54(2):8.)
Emil August Goeldi (1859-1917), a naturalist from Switzerland, was invited by the government of Brazil to investigate the decline of coffee trees growing in the
Local coffee producers had alerted the Emperor to their problem several years earlier and Clément Jobert, a French researcher, had already published (1878) a brief note speculating that the causal agent was a nematode of the genus
In 1897, Goeldi p
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Coffee-producing areas of Central and South America and southern India, China, and some southern European countries (Elling, 2013).
Meloidogyne exigua is present in 22% of the coffee plantations and 95% of the districts in southern Minas Gerais State in Brazil; that region accounts for nearly half of Brazil's coffee production (Elling, 2013).
C-rated pests in California.
Sedentary endoparasite.
Feeding site establishment and development typical of genus.
Type Host: Coffee (Coffea sp.)
Coffee, banana, watermelon, pepper, tomato, onion, sugarcane, citrus, rice, rubber tree, and weeds (e.g., Taraxacum officinale, Amaranthus deflexus, and Poinsetta heterophylla).
All the main coffee cultivars grown are susceptible to M. exigua nematode and germplasm screens have failed to identify resistance in Coffea arabica (Elling, 2013).
However, resistance to M. exigua in coffee plants is conferred by the gene Mex-1 from Coffea canephora. The main strategy for developing cultivars that are resistant to M. exigua is by transferring the resistance gene from C. canephora to C. arabica by back crosses. The resistance is conferred by ar least one dominant gene, Mex-1. Some galls formed on C, arabica with the Mex-1 but there was no reproduction or egg mass formartion.(Noir et al., 2003; Oliveira et al, 2013).
Ecophysiological Parameters:
Haploid chromosome number n=18; reproduction is by facultative meiotic parthenogenesis. The egg nucleus undergoes a meiotic reduction division; one member of each pair of chromatids remains in a haploid nucleus and the other in a polar body. If fertilization by a male sperm occurs, the diploid number of chromosomes is restored. Otherwise the somatic number of chromosomes is restored by fusion of the egg pronucleus with the polar body from the reduction division (Subbotin et al., 2021; Triantaphyllou, 1985).
Feeding causes yellowing of leaves, leaf fall, destruction of root hairs and rootlets, root lesions, small root galls, vascular disruption, and secondary invasion. Yields of non-infested plants may be twice as high as those infested with M. exigua (Lordello, 1986).
Coffee yield losses estimated at 10-20% in Costa Rica and 45% in Brazil.
Root necrosis and defoliation are greater when roots are infected by both M. exigua and Rhizoctonia solani than by either organism alone. Meloidogyne exigua typically induces round galls on coffee roots with egg masses within the galls (Humphreys=Pereira et al., 2014).
Treatment of seedbeds with nematicides is effective; however, use of nematicides on established coffee plants is not feasible due to phytotoxicity and expense.
Produce coffee seedlings in nurseries where soil has been disinfested.
In Minas Gerais, Brazil, the best time to implement chemical control measures against M. exigua is November, which coincides with renewed plant root growth, a high level of lipid reserves in J2, high nematode population density, and high infectivity (Elling, 2013).
Host Plant Resistance, Non-hosts and Crop Rotation alternatives:
Although there is no known resistance in Coffea arabica, resistant rootstocks are available, but yield is lower. Coffeae canephora cv robusta is highly resistant to M. exigua via the dominant gene Mex-1.
One year fallow period recommended before replanting an infested coffee plantation in Brazil.
Elling, A.A. 2013. Major emerging problems with minor Meloidogyne species. Phytopathology 103:1092-1102.
Goeldi, E.A. 1887. Relatorio sobre a molestia do cafeeiro na provincia do Rio de Janeiro. Archivos do Museo Nacional 8:7-123 (1892)
Humphreys-Pereira, D.A., Flores-Chavez, L., Gomez, M., Salazar, L. Gomez-Alpizar, L.E., Elling, A.A. 2014. Meloidogyne lopezi n.sp. (Nematode: Meloidogynidae, a new root-knot nematode. . Nematology 16:643-661.
Lordello, L.G.E. 1986 Plant-parasitic nematodes that attack coffee. Pp 33-41 in Anon. Plant-parasitic nematodes of bananas, citrus, coffee, grapes and tobacco. Union Carbide Corp.
Noir S, Anthony F, Bertrand B, Combes MC, Lashermes P (2003) Identification of a major gene (Mex-1) from Coffea canephora conferring resistance to Meloidogyne exigua in Coffea arabica. Plant Pathology 52:97-103
Silva, R., Oliviera, R., Ferreira, P., Ferreira, A., Rodrigues, F. 2013. Defense responses to Meloidogyne exigua in resistant coffee cultivar and non-host plant. Tropical Plant Pathology 38:114-121.
Subbotin, S.A. Palomares-Rius, J.E., Castillo, P. 2021. Systematics of Root-knot Nematodes (Nematoda: Meloidogynidae). Nematology Monographs and Perspectives Vol 14: D.J. Hunt and R.N. Perry (eds) Brill, Leiden, The Netherlands 857p.
Triantaphyllou, A.C. 1985. Gametogenesis and the chromosomes of Meloidogune nataliei: not typical of other root-knot nematodes. J. Nematology 17:1-5.
Triantaphyllou, A.C. 1985. Cytogenetics, cytotaxonomy and phylogeny of root-knot nematodes. In Sasser, J.N. & Carter, C.C. (eds) An Advanced Treatiswe on Meloidogyne.Vol 1. Biology and Control.N.C. State Universty Graphics, Raleigh, N.C. USA.