First Report of Stubby-Root Nematode, Paratrichodorus minor, on Onion in Georgia, U.S.A

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Journal of Nematology

Society of Nematologists

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ISSN: 0022-300X
eISSN: 2640-396X

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VOLUME 50 , ISSUE 3 (September 2018) > List of articles

First Report of Stubby-Root Nematode, Paratrichodorus minor, on Onion in Georgia, U.S.A

Abolfazl Hajihassani * / Negin Hamidi / Bhabesh Dutta / Chris Tyson

Keywords : Detection, Georgia, P. minor, Sweet onion

Citation Information : Journal of Nematology. VOLUME 50 , ISSUE 3 , ISSN (Online) 2640-396X, DOI: 10.21307/jofnem-2018-038, September 2018 © 2018.© The Society of Nematologists

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Published Online: 17-October-2018

ARTICLE

ABSTRACT

Onions (Allium cepa L.) are the leading vegetable crop in Georgia accounting for 13.7% of total state vegetable production (Wolfe and Stubbs, 2017). In November 2017, two samples each of onion (var. Candy Ann) seedlings and soil were received from the University of Georgia Cooperative Extension office in Tattnall County, GA. The samples were collected from a nursery fumigated with metam sodium and used for sweet onion transplant production. Symptoms of the damaged plants included stunted growth both in the root system and foliage, tip die-back of the leaves (Fig. 1A,B), and slight swelling at the tip of roots. Vermiform life stages from the soil samples were extracted using centrifugal-flotation technique (Jenkins, 1964). On an average, 67 stubby-root nematodes per 100 cm3 of soil were obtained. Additional two soil samples were collected from the nursery in December 2017 to confirm the presence of the nematode. On an average, 1 and 75 nematodes per 100 cm3 of soil were recovered from areas with healthy and infested plants, respectively. Because the male individuals were not found in the soil samples, females were used for species identification. Morphological and molecular analyses of females (Fig. 2A-C) identified the species as Paratrichodorus minor (Colbran) Siddiqi; (Decraemer, 1995). Nematode body shape was “cigar-shaped” with dorsally curved “onchiostyle” stylet Females had an oval-shaped vagina, vulva a transverse slit, and lateral body pores were absent. The measurements of females (n = 20) included: body length 671.1 (570.1–785.3) µm; body width 32.5 (27.8–37.0) µm; onchiostyle 32.5 (31.1–34.8) µm; anterior end to esophagus-intestinal valve 117.6 (101.2–128.5) µm; a 21.5 (15.3–28.1) µm; b 5.2 (4.9–6.3) µm; V 52.9% (48.1–55.4%) µm; and vagina length 8.7 (7.8–10.7) µm. To confirm the identity of P. minor, DNA was extracted from single females (n = 3) using Extract-N-Amp Tissue PCR Kit (Sigma-Alredich Inc., St. Louis, MO). The partial 18S rRNA, the D2-D3 expansion segments of 28S rRNA, and ITS1 rDNA were amplified using primer pairs 360F (5′ CTACCACATCCAAGGAAGGC 3′)/932R (5′ TATCTGATCGCTGTCGAACC 3′), D2A (5′ ACAAGTACCGTGAGGGAAAGTTG 3′)/D3B (5′ TCGGAAGGAACCAGCTACTA 3′), and BL18 (5′ CCCGTCGCTACTACCGATT 3′)/5818 (5′ ACGARCCGAGTGATCCAC 3′), respectively (Riga et al., 2007; Duarte et al., 2010; Ye et al., 2015; Shaver et al., 2016). The obtained PCR fragments were purified using QIAquick Gel Extraction Kit (Qiagen Inc., Santa Clara, CA, USA), sequenced and deposited in the GenBank databases (18S rRNA: MG856931; 28S rRNA: MG856933; ITS1 rDNA: MH464152). The 18S rRNA, 28S D2-D3, and ITS1 rDNA sequences shared 99% similarity (100% coverage) with GenBank accessions of P. minor from California, Arkansas, and China (18S rRNA: JN123365; 28S D2-D3: JN123395; ITS1 rDNA: GU645811). In a pathogenicity test, five sweet onion seeds var. Pirate were planted (one per pot) in 11.5-cm-diameter polyethylene pots containing 1,000 cm3 of equal parts of pasteurized field soil and sand, and then inoculated with 1,000 fresh P. minor. Plants were grown for 9 wk in a greenhouse at 25 ± 2°C prior to extraction of nematodes from soil. Plant roots were abbreviated and final population density of P. minor was 2,856 ± 104 per pot (285 nematodes/100 cm3 of soil) confirming the nematode parasitism on onion. To our knowledge, this is the first report of P. minor parasitizing onion in Georgia. Stubby-root nematode (Paratrichodorus sp.) has already been reported on corn, St. Augustine grass, and switchgrass in Georgia (Heald and Perry, 1969; Davis and Timper, 2000; Mekete et al., 2011). In the U.S.A, P. minor is known to occur on diverse crops in most of the states (Decraemer, 1995; CABI/EPPO, 2002). A survey of vegetable-producing areas in Georgia is currently under investigation to determine the distribution of this economically important nematode species.

Damage symptoms caused by stubby-root nematode Paratrichodorus minor on sweet onion in Georgia. A large area of stunted and chlorotic plant foliage (A); Infested seedlings with abbreviated roots and necrotic leaf tips (B).

Light microscopy micrographs showing morphological characters of stubby-root nematode, Paratrichodorus minor. Entire body (A), anterior end (B), and posterior region (C) of female nematode.

Graphical ABSTRACT

References


  1. CABI/EPPO. 2002. Paratrichodorus minor. Distribution maps of plant diseases. 1st ed., October, Map 870, CABI Publishing, Wallingford, UK.
  2. Crow, W. T.. 2005. Diagnosis of Trichodorus obtusus and Paratrichodorus minor on turfgrasses in the Southeastern United States. Plant Health Progress. www.plantmanagementnetwork.org/pub/php/diagnosticguide/2005/stubby/.
    [URL]
  3. Decraemer, W.. 1995. The family trichodoridae: stubby root and virus vector nematodes, Kluwer Academic Publishers, Dordrecht, The Netherlands.
  4. Davis, R. F., and Timper, P.. 2000. Survey of nematodes associated with corn in Georgia. Journal of Nematology 32 4: 26.
  5. Duarte, I. M., De Almeida, M. T. M., Brown, D. J. F., Marques, I., Neilson, R., and Decraemer, W.. 2010. Phylogenetic relationships, based on SSU rDNA sequences, among the didelphic genera of the family Trichodoridae from Portugal. Nematology 12 2: 171–80.
    [CROSSREF]
  6. Jenkins, W. R.. 1964. A rapid centrifugal-flotation technique for separating nematodes from soil. Plant Disease Reporter 48 9: 692.
  7. Heald, C. M., and Perry, V. G.. 1969. Nematodes and other pests. in Hanson, A. A., and Juska, F. V. (Eds), Turfgrass science, American Society of Agronomy, Madison, WI: 358–69.
  8. Mekete, T., Reynolds, K., Lopez-Nicora, H. D., Gray, M. E., and Niblack, T. L.. 2011. Plant-parasitic nematodes are potential pathogens of Miscanthus × giganteus and Panicum virgatum used for biofuels. Plant Disease 95 4: 413–8.
    [CROSSREF]
  9. Riga, E., Karanastasi, E., Oliveira, C. M. G., and Neilson, R.. 2007. Molecular identification of two stubby root nematode species. American Journal of Potato Research 84 2: 161–7.
    [CROSSREF]
  10. Shaver, J. B., Marchant, S., Martin, S. B., and Agudelo, P.. 2016. 18S rRNA and COI haplotype diversity of Trichodorus obtusus from turfgrass in South Carolina. Nematology 18 1: 53–65.
    [CROSSREF]
  11. Ye, W., Zeng, Y., and Kerns, J.. 2015. First report of Trichodorus obtusus on turfgrass in North Carolina, U.S.A. Plant Disease 99 2: 291.
    [CROSSREF]
  12. Wolfe, K., and Stubbs, K.. 2017. 2016 Georgia farm gate value report. Center for Agribusiness and Economic Development, University of Georgia, Athens, Georgia, available at: http://caes2.caes.uga.edu/center/caed/pubs/documents/2016CAEDFarmGateValueReport.pdf.
    [URL]
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FIGURES & TABLES

Figure 1

Damage symptoms caused by stubby-root nematode Paratrichodorus minor on sweet onion in Georgia. A large area of stunted and chlorotic plant foliage (A); Infested seedlings with abbreviated roots and necrotic leaf tips (B).

Full Size   |   Slide (.pptx)

Figure 2

Light microscopy micrographs showing morphological characters of stubby-root nematode, Paratrichodorus minor. Entire body (A), anterior end (B), and posterior region (C) of female nematode.

Full Size   |   Slide (.pptx)

REFERENCES

  1. CABI/EPPO. 2002. Paratrichodorus minor. Distribution maps of plant diseases. 1st ed., October, Map 870, CABI Publishing, Wallingford, UK.
  2. Crow, W. T.. 2005. Diagnosis of Trichodorus obtusus and Paratrichodorus minor on turfgrasses in the Southeastern United States. Plant Health Progress. www.plantmanagementnetwork.org/pub/php/diagnosticguide/2005/stubby/.
    [URL]
  3. Decraemer, W.. 1995. The family trichodoridae: stubby root and virus vector nematodes, Kluwer Academic Publishers, Dordrecht, The Netherlands.
  4. Davis, R. F., and Timper, P.. 2000. Survey of nematodes associated with corn in Georgia. Journal of Nematology 32 4: 26.
  5. Duarte, I. M., De Almeida, M. T. M., Brown, D. J. F., Marques, I., Neilson, R., and Decraemer, W.. 2010. Phylogenetic relationships, based on SSU rDNA sequences, among the didelphic genera of the family Trichodoridae from Portugal. Nematology 12 2: 171–80.
    [CROSSREF]
  6. Jenkins, W. R.. 1964. A rapid centrifugal-flotation technique for separating nematodes from soil. Plant Disease Reporter 48 9: 692.
  7. Heald, C. M., and Perry, V. G.. 1969. Nematodes and other pests. in Hanson, A. A., and Juska, F. V. (Eds), Turfgrass science, American Society of Agronomy, Madison, WI: 358–69.
  8. Mekete, T., Reynolds, K., Lopez-Nicora, H. D., Gray, M. E., and Niblack, T. L.. 2011. Plant-parasitic nematodes are potential pathogens of Miscanthus × giganteus and Panicum virgatum used for biofuels. Plant Disease 95 4: 413–8.
    [CROSSREF]
  9. Riga, E., Karanastasi, E., Oliveira, C. M. G., and Neilson, R.. 2007. Molecular identification of two stubby root nematode species. American Journal of Potato Research 84 2: 161–7.
    [CROSSREF]
  10. Shaver, J. B., Marchant, S., Martin, S. B., and Agudelo, P.. 2016. 18S rRNA and COI haplotype diversity of Trichodorus obtusus from turfgrass in South Carolina. Nematology 18 1: 53–65.
    [CROSSREF]
  11. Ye, W., Zeng, Y., and Kerns, J.. 2015. First report of Trichodorus obtusus on turfgrass in North Carolina, U.S.A. Plant Disease 99 2: 291.
    [CROSSREF]
  12. Wolfe, K., and Stubbs, K.. 2017. 2016 Georgia farm gate value report. Center for Agribusiness and Economic Development, University of Georgia, Athens, Georgia, available at: http://caes2.caes.uga.edu/center/caed/pubs/documents/2016CAEDFarmGateValueReport.pdf.
    [URL]

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