Nacobbus aberrans

  

Contents

  

Rev 10/16/2008

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
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Classification:

      Tylenchida
       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


N. 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.

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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 Cid del Prado)

Males:

Vermiform and of the same body length as females.

Caudal alae peloderan.

Spicules and gubernaculum.

 
 
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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 pests in California.

 

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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.

 

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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 (Lycopersicon esculentum), 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:

Eggs are deposited in a gelatinous matrix; some may be retained in the body.

 

The first molt occurs within the egg; the J2 stage is infective and penetrates host roots.  Subsequent motls 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.

 

Life cycle is approximately 48 days at 25 C.

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 60 to 100 d.a.t. and the third  >100 d.a.t.. (Cristóbal, 2001).

Most favorable conditions for N. aberrans development include sand to sandy-loam soils, temperature range between 15 and 23°C 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).

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Damage:

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 Cid del Prado)
   

 

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Management:

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.

 
   
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References:

Baldwin and Cap, 1992.

Inserra, Griffin & Anderson, (1985).  The False Root-Knot Nematode Nacobbus aberrans. 

Stone, A.R. and P.R. Burrows. 1985. Nacobbus aberrans. CIH 119.

Cid del Prado Vera, F. Franco J.C. Alejo, R. Flores C., J.A. Hernandez, R. Manzanilla L. and K. Evans. 2005.  Characteristics and Ecology of Nacobbus aberrans in Mexico.  California Nematology Workshop.

 

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Copyright © 1999 by Howard Ferris.
Revised: October 16, 2008 .