Nacobbus aberrans		Contents		Rev 11/19/2024
False Root-knot Nematode		Classification		Hosts
		Morphology and Anatomy		Life Cycle
Return to Nacobbus Menu		Economic Importance		Damage
		Distribution		Management
Return to Pratylenchidae Menu		Feeding		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

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Classification:

        Tylenchina
        Tylenchoidea
         Pratylenchidae
          Nacobbinae

    Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944

    Sugarbeet False Root-knot Nematode

Synonyms:

 Anguillulina aberrans Thorne, 1935

Pratylenchus aberrans (Thorne, 1935) Filipjev, 1936

Nacobbus batatiformis Thorne & Schuster, 1959

Nacobbus serendipiticus Franklin, 1959

Nacobbus serendipiticus bolivianus Lordello, Zamith & Boock, 1961

Nacobbus aberrans is considered synonymous with N. batatiformis (Gerald Thorne called Sher a fool in correspondence over the taxonomy).  However, there is considerable disagreement regarding the taxonomy of N. aberrans  (Sher, 1970; Baldwin & Cap, 1992) and some consider N. aberrans sensu lato to include N. batatiformis, N. serendipiticus and N. aberrans sensu stricto.

Molecular, morphological and host range studies suggest that N. aberrans is a species complex with at least three groupings.  A North/South American group includes populations from Mexico, Argentina and Ecuador; and two South American groups that include one from Argentina and another from Bolivia and Peru.  The latter has been characterised as the original N. serendipiticus bolivianus of Lordello, Zamith and Boock, 1961 now elevated to species status as N. bolivianus.

	DNA sequences suggest three groupings of the Nacobbus aberrans species complex: i) North/South American group of populations from Mexico, Argentina and Ecuador; South American group of by populations from Argentina; and Nacobbus bolivianus represented by populations from Peru and Bolivia.  Overlap of circles represents shared DNA sequences. Diagram from Manzanilla-López et al. (2010).

 

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Morphology and Anatomy:

	Immature Females: length 1mm. vermiform. tylenchid stylet with well developed basal knobs; head not off-set; esophageal gland overlapping the intestine dorsally; lateral field with four incisures; monovarial vulva close to the anus, sub-terminal
	Mature Females: saccate (0.8 to 1.4 mm long and 0.2 to 0.45 mm wide);
Mature females; whole nematode (left), posterior (upper right), anterior (lower right) (Photographs by IgnacioCid del PradoVera)
	Males: Vermiform and of the same body length as females. Caudal alae peloderan. Spicules and gubernaculum.	Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

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Distribution:

Nebraska, Wyoming, Utah, Colorado, Montana, South Dakota, Kansas in USA.

Also occurs in England, the Netherlands, South America, and Mexico.

Distribution of Nacobbus aberrans in Mexico, 2005 (Cid del Prado et al., 2005)

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Economic Importance:

 A-rated pest in California Nematode Pest Rating System (Martin, 2024)

Nacobbus aberrans is economically important in temperate and subtropical latitudes of North and South America. The host range,
which includes at least 84 plant species. Many common weeds are good hosts.

Populations can be separated into bean, potato and sugarbeet groups. The populations of each group have distinct host preferences.
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Reported yield losses reported average 65% for potato in the Andean region of Latin America, 55% and 36% for tomato and bean in Mexico, respectively, and 10-20% for sugarbeet in the United States (Nebraska).

Ref. Manzanilla-Lopez et al. (2002).

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Feeding:

All juveniles are migratory endoparasites and penetrate plant root tips and/or axial roots.  Juvenile penetration induces slight swellings on sugarbeet and tomato roots at their axis and tips.  However, potato roots invaded by juveniles exhibit lesions with discolored tissues.  On sugarbeets, the swellings may extend over a large portion of the root axis.   Mature females penetrate roots, become swollen and sedentary, cause formation of root galls and enlarged cells. The feeding site is a multinucleate syncytium formed by cell wall breakdown.

Nacobbus aberrans populations, which parasitize sugarbeet in the western US do not parasitize potato.  Similarly, populations in Mexico do not parasitize potato.  However, many South American populations infect both potato and sugarbeet. 

Comparison of the galling symptoms caused by Nacobbus aberrans and Meloidogyne incognita on tomato. Left: the "rosary bead" pattern typical of Nacobbus and the coalesced galling of a heavy Meloidogyne infection. Photographs by Marco Antonio Magallanes Tapia, PhD Thesis, Colegio de Postgraduados, Texcoco, Mexico, 2021

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Hosts:

Potatoes, sugarbeets, beans, peppers, crucifers, Solanaceae, e.g., tomato, but not Poaceae (grasses).

Nacobbus aberrans has a wide host range; important commercial crops affected in South America and the United States are potato and sugarbeet, respectively.  

Bean, pepper, and tomato are among the most important hosts of this nematode in South America and Mexico.  

Infests plants of the families Apiaceae, Brassicaceae, Cactaceae, Chenopodiaceae, Cucurbitaceae, Fabaceae, Solanaceae and Zygophyllaceae. It is found on important food crops, such as cabbage, carrot, cucumber, lettuce, mustard, pea, potato, sugarbeet and tomato (Canto, 1992).

The known host range of N. aberrans includes: Austrian winter pea (Pisum sativum var. arvense), sweetpotato (Ipomoea batatas), beet (Beta vulgaris), broccoli, Brussel sprouts, cabbage, collard and kohlrabi (Brassica oleracea), carrot (Daucus carota), cucumber (Cucumis sativus), egg plant (Solanum melogena), grain amaranth (Amaranthus sp.), (Brassica oleracea), lettuce (Lactuca sativa), mashua (Tropaeolum tuberosum), ornamental gourd (Cucurbita pepo), pepper (Capsicum annuum and C. baccatum), potato (Solanum tuberosum), prickly pear (Opuntia sp.), pumpkin (Cucurbita maxima), spinach (Spinacia oleracea), sugarbeet (Beta vulgaris), tobacco (Nicotiana tabacum), tomato (Solanum lycopersicum), turnip (Brassica rapa).

Other hosts may be common weeds, including black mustard (Brassica nigra), chickweed (Stellaria media), corn spurry (Spergula arvensis), fat hen (Chenopodium album), fireweed (Datura ferox), ground cherry (Physalis), London rocket (Sysimbrium irio), kochia (Kochia scoparia), lambsquarter (Chenopodium album), nightshade (Solanum nigrum), oregano (Origanum vulgare), puncture vine (Tribulus terrestris), purslane (Portulaca oleracea), quinoa (Chenopodium quinoa), saltwort (Salsola kali), and shadescale (Atriplex confertifolia) (Brodie, et al., 1993; CAB International, 2001; Canto, 1992; Society of Nematologists).

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Life Cycle:

Ecophysiological Parameters:

Eggs are deposited in a gelatinous matrix; some may be retained in the posterior part of the body.  This is different from N. dorsalis in which the eggs are retained in the body.

The first molt occurs within the egg; the J2 stage is infective and penetrates host roots.  Subsequent molts occur in either roots or soil.  The immature female moves to the root cortex and gall formation occurs as the nematode feeds.  The posterior of the female extends towards the outside of the root and eggs are deposited in a matrix.  Males may be entangled in the matrix suggesting that copulation occurs after the feeding site is established and females have started to swell. Reproduction in N. aberrans is probably sexual, although there are some suggestions that parthenogenesis may occur (Manzanilla-Lopez et al. 2002).

 Life cycle is approximately 48 days at 25 C.

Nacobbus aberrans can survive unfavorable environmental conditions, such as extremely low soil humidity and low temperatures, by entering a quiescent dormant stage (Anthoine et al., 2006).

In tomato crops in Mexico there are 3 generations: the first is completed between 0 and 60 days after transplanting (d.a.t.), the second at 60 to 100 d.a.t. and the third at  >100 d.a.t.. (Cristobal, 2001).

Most favorable conditions for N. aberrans development include sand to sandy-loam soils, temperature range between 15 and 23C and 5 and 19% soil moisture (Cruz et al., 1987).

In Mexico, N. aberrans J3 and J4 survive under field conditions without a host for one year.  The  J3 and J4 stages, possibly in an anhydrobiotic state, are the primary inoculum infecting susceptible hosts the next year.  Survival of J3 and J4 increases if they are in root fragments. Eggs and J2 do not survive without a host or under adverse conditions (Cid del Prado et al, 2005; Stone and Burrows, 1985).

Egg mass produced by Nacobbus aberrans female on the surface of a gall on tomato root Photograph by Ignacio Cid del Prado Vera

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Damage:

Invasion and migration through plant roots creates tissue damage and easy access for other pathogens.  Mature femalesbecome secondary and create unique syncytial feedingsites. Sycnytia are formed through cell division, degradation of neighboring call walls and protoplast fusion Consequently, syncytia are multinuclate and are locations of elevated metabolic activity.. Galls are produced around these feeding sites from the proliferation of vascular and cortical tissue (Inserra et al., 1983).

The degree of yield losses caused by this nematode depends primarily on soil population densities.  

In western Nebraska, complete destruction of sugarbeet seedlings has been observed in heavily infested fields.

[Ref: Inserra, et al. (1985).] 

Galled tomato root, Mexico (photograph by Ignacio Cid del Prado Vera)	Nacobbus aberrans in greenhouse-grown tomatoes, Texcoco  Mexico State, Mexico (photograph by Ignacio Cid del Prado Vera)
	Nacobbus aberrans Greenhouse-grown   tomato (cv El Cid) Texcoco, Mexico Photographs by  Ignacio Cid del Prado Vera

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Management:

Exclusion:  The ability of South American populations to adapt to many hosts and to diverse conditions increases the risk of their establishment in new locations.  Exclusion efforts on a national and regional basis are important.

Nematicides

Fumigants (e.g., Telone II) are most effective.

Non-fumigants, such as Aldicarb, oxamyl, and phenamiphos also look promising.

Host Plant Resistance

	Tests in Mexico:
	In chili pepper: Of 90 varieties and lines of Capsicum spp., all were susceptible.  Only Capsicum pendulum = C. baccatum was considered tolerant.
	In tomato: All varieties (wild, criollas, hybrid) tested in the greenhouse (60) and in the field (81) were susceptible to N. aberrans.
	In beans: Only four varieties were resistant.
Resistance Host Plant Resistance, Non-hosts and Crop Rotation alternatives: For plants reported to have some level of resistance to this species, click
Cultural Practices Combinations of organic amendments of plant origin, animal manures, the parasitic fungus Pochonia chlamydosporia and biofumigation have been very effective in greenhouse tomato production in Mexico. Nacobbus aberrans Biofumigation experiment Greenhouse tomatoes Texcoco, Mexico Dr. Ignacio Cid del Prado       Nacobbus aberrans in Mexico (I. Cid del Prado - Powerpoint)

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References:

Anthoine, G., Gauthier, J.P. and Mugniery, D. 2006. Aspects of the biology of Nacobbus aberrans (Thorn, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae): 1 - Capacities of quiescence and diapause. Bulletin OEPP,36, 359-364

Baldwin, J.H. and Cap, G.B. 1992. Systematics of Nacobbus, the false root-knot nematode.  In: Gommers, F.J. and Maas, P.W.Th. (Eds).  Nematology from molecule to ecosystem.  Europeann Soc. Nematologists. Dundee.