False columbia root-knot nematode - Meloidogyne fallax
EEffective: August 18, 2010 - December 31, 2020
Screening Aids:
Taxonomic Position:
Tylenchida : Heteroderidae
Pest Type:
Nematodes
Pest Code (NAPIS):
NEOBQEA
This pest is a member of the following lists:
| Solanaceous Hosts |
|---|
These Approved Methods are appropriate for:
2020, 2019, 2018, 2017, 2016, 2015
Pest is vectored by:
This pest is is not known to be a vector and it is not vectored by any organism.
Survey
Approved Method(s):
| Method | Instructions | NAPIS Survey Method |
|---|---|---|
| Soil Sample | Send sample to nematology diagnostic lab where nematodes will be extracted and identified. |
3012 - General Soil Sample |
| Visual | Collect symptomatic tubers. |
3031 - General Visual Observation |
Survey Instruction Details:
The presence of M. fallax in infested soil can be determined by sampling and extraction of the second-stage juveniles, using a standard nematode extraction procedure for free-living nematodes of this size or techniques used for root-knot nematodes (Baermann trays, Baermann trays with elutriation or sieving, centrifugal flotation, flotation-sieving, semiautomatic elutriation and Cobb decanting and sieving).
Signs:
Adult females are visible just below the surface; when alive they appear as glistening, white, pear-shaped bodies surrounded by a brownish layer of host tissue. As the female matures and dies, the egg-filled sac becomes dark-brown with age. Potato roots may also be infected, but this is difficult to detect without a magnifying lens, as little or no galling occurs, even in heavy infestations. The spherical bodies of females may protrude from the surface of small rootlets surrounded posteriorly by a large egg-filled sac, which becomes dark-brown with age.
Symptoms:
On potato: Symptoms are very similar to those caused by M. chitwoodi. Above-ground symptoms are often not obvious but may consist of varying degrees of stunting, lack of vigor, and a tendency to wilt under moisture stress, all leading to reduced yield. Infested potato tubers may have small raised swellings, as compared with the large easily noticeable galls of other Meloidogyne spp., on their surface above the developing nematodes. A number of galls may be concentrated on one area of the tuber or single galls may be scattered near eyes or lesions. Internal tissue below the gall is necrotic and brownish.
On turf: There are numerous root knot nematodes which cause turf damage, and symptoms are similar for each nematode. Symptoms include yellowing and death of grass, root stunting, death of roots, and knots on roots. However, visual symptoms alone are similar to symptoms of nutrient deficiency, lack of moisture, and other diseases. Soil samples must be taken to verify the presence of nematodes.
On turf: There are numerous root knot nematodes which cause turf damage, and symptoms are similar for each nematode. Symptoms include yellowing and death of grass, root stunting, death of roots, and knots on roots. However, visual symptoms alone are similar to symptoms of nutrient deficiency, lack of moisture, and other diseases. Soil samples must be taken to verify the presence of nematodes.
Key Diagnostics
ID/Diagnostic: Morphological
Morphological: Characteristics of the males, females, and juveniles (Karssen, 1996).
Mistaken Identities:
Meloidogyne fallax is morphologically similar to and was initially considered a race of M. chitwoodi.
Unless very closely examined, M. fallax, M. chitwoodi, and M. hapla may be easily confused. M. fallax has also been misidentified as M. incognita and M. minor.
In Progress / Literature-based Diagnostics:
Molecular: Common molecular techniques to identify M. fallax include RFLP, SCAR, and RAPD-based procedures.
Petersen and Vrain (1996) and Wishart et al. (2002) developed PCR primers to identify M. chitwoodi, M. hapla, and M. fallax.
Zijlstra (1997) used a multiplex PCR to distinguish M. hapla, M. chitwoodi, M. fallax, and M. incognita. Zijlstra (2000) used SCAR-PCR to identify M. hapla, M. chitwoodi, and M. fallax.
Update: This PCR was designed before the description of M. minor, and subsequent research by Nischwitz et al. (2013) showed that M. minor amplification also occurs and cannot be distinguished from M. fallax using this SCAR-PCR. Therefore, it is not advised to use this protocol if a mixed presence of both M. fallax and M. minor is possible in the same sample.
Adam et al. (2007) developed a molecular diagnostic key to identify juveniles of seven species, including M. incognita, M. javanica, M. arenaria, M. mayaguensis, M. hapla, M. chitwoodi, and M. fallax. Petersen et al. (1997) used a multiplex PCR to distinguish the juveniles and eggs of the same seven species. Fourie et al. (2001) distinguished the same species except M. mayaguensis.
A real-time PCR for the simultaneous detection of M. fallax and M. chitwoodi has been developed (Zijlstra and van Hoof, 2006).
Nischwitz et al. (2013) describe a method to distinguish M. fallax from M. minor and M. chitwoodi by amplification and sequencing of Hsp90 genomic DNA.
Petersen and Vrain (1996) and Wishart et al. (2002) developed PCR primers to identify M. chitwoodi, M. hapla, and M. fallax.
Zijlstra (1997) used a multiplex PCR to distinguish M. hapla, M. chitwoodi, M. fallax, and M. incognita. Zijlstra (2000) used SCAR-PCR to identify M. hapla, M. chitwoodi, and M. fallax.
Update: This PCR was designed before the description of M. minor, and subsequent research by Nischwitz et al. (2013) showed that M. minor amplification also occurs and cannot be distinguished from M. fallax using this SCAR-PCR. Therefore, it is not advised to use this protocol if a mixed presence of both M. fallax and M. minor is possible in the same sample.
Adam et al. (2007) developed a molecular diagnostic key to identify juveniles of seven species, including M. incognita, M. javanica, M. arenaria, M. mayaguensis, M. hapla, M. chitwoodi, and M. fallax. Petersen et al. (1997) used a multiplex PCR to distinguish the juveniles and eggs of the same seven species. Fourie et al. (2001) distinguished the same species except M. mayaguensis.
A real-time PCR for the simultaneous detection of M. fallax and M. chitwoodi has been developed (Zijlstra and van Hoof, 2006).
Nischwitz et al. (2013) describe a method to distinguish M. fallax from M. minor and M. chitwoodi by amplification and sequencing of Hsp90 genomic DNA.
References
- Adam, M.A.M., Phillips, M.S., and Blok, V.C. 2007. Molecular diagnostic key for identification of single juveniles of seven common and ecologically important species of root-knot nematode (Meloidogyne spp.). Plant Pathology 56: 190-197.
- Fourie, H., Zijlstra, C., and McDonald, A.H. 2001. Identification of root-knot nematode species occurring in South Africa using the SCAR-PCR technique. Nematology 3(7): 675-680.
- Karssen, G. 1996. Description of Meloidogyne fallax n. sp. (Nematoda : Heteroderidae), a root-knot nematode from The Netherlands. Fundamental and Applied Nematology 19: 593-599.
- Nischwitz, C., Skantar, A., Handoo, Z., Hult, M., Schmitt, M., and McClure, M. 2013. Occurrence of Meloidogyne fallax in North America, and molecular characterization of M. fallax and M. minor from U.S. golf course greens. Plant disease 97: 1424-1430.
- Petersen, D.J., and Vrain, T.C. 1996. Rapid identification of Meloidogyne chitwoodi, M. hapla, and M. fallax using PCR primers to amplify their ribosomal intergenic spacer. Fundam. Appl. Nematol. 19(6): 601-605.
- Wishart, J., Phillips, M.S., and Blok, V.C. 2002. Ribosomal intergenic spacer: a polymerase chain reaction diagnostic for Meloidogyne chitwoodi, M. fallax, and M. hapla. Phytopathology 92: 884-892.
- Zijlstra, C. 1997. A fast PCR assay to identify Meloidogyne hapla, M. chitwoodi, and M. fallax, and to sensitively differentiate them from each other and from M. incognita in mixtures. Fundam. Appl. Nematol. 20: 505-511.
- Zijlstra, C., and van Hoof, R.A. 2006. A multiplex real-time polymerase chain reaction (TaqMan) assay for the simultaneous detection of Meloidogyne chitwoodi and M. fallax. Phytopathology 96: 1255-1262.