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Tylenchina Tylenchoidea Pratylenchidae Pratylenchinae Pratylenchus vulnus
Root Lesion Nematode
|Male with small bursa extending to tail tip, and simple gubernaculum|
Feeds mainly in cortex; may penetrate xylem, but rarely the phloem.
Over 80 hosts, including fruits, nuts, peaches, grapevines, soybeans and others.
Many hosts are woody perennials.
For an extensive list of host plant species and their susceptibility, copy the name
select Nemabase and paste the name in the Genus and species box
Males and females are present.
|Smaller roots may be killed by nematode feeding.|
Carignane grape roots grown in soil from a walnut orchard infested with P. vulnus (left); in same soil treated with 1,3-D nematicide (right).
Pratylenchus vulnus damage to walnuts:
Stunted trees, dieback.
Nematicides: Preplant treatment of 1,3-Dichloropropene (1,3-D) followed by 2.5 gal/acre DBCP annually in tree crops was very effective, however DBCP is no longer available. Postplant treatments with Nemacur (phenamiphos) can be effective.
Hot water treatments: (5 min at 51.7 C) eradicates this species from grapevine roots.
Tolerant Rootstocks: Some walnut rootstocks are reputed to show tolerance. e.g., hybrids of Juglans hindsii and Juglans regia - cv Paradox.
|Myrobalan 29C plum rootstock appears more tolerant to P. vulnus than Lovell peach rootstock.||Plum on Myrobalan 29C rootstock (left) and on Lovell
rootstock (right) in soil infested with P. vulnus.
Experiment by M.V. McKenry at Kearney Agricultural Center, Parlier, California.
Resistant Rootstocks: There is a large rootstock screening and development program at the USDA Fresno station for resistance and tolerance to P. vulnus (Dr. Craig Ledbetter).
The Paradox diversity study recognizes that Paradox hybrids (J. regia x J. hindsii hybrids are all genetically different seedlings. Some may be more resistant or tolerant than others to P. vulnus. The hybrids are sterile, so if useful rootstocks are found in the project, the development of vegetative propagation will be critical.
Consider transgenic options with rootstocks:
Mycogen corp. (San Diego) reportedly isolated Bacillus thuringiensis (Bt) strains effective against Pratylenchus spp. and later transferred the rights to Monsanto Corporation. The Bt gene responsible for toxin production effective against certain insect pests has been transgenically inserted into the genome of some plants; a similar strategy would probably work against nematodes with the nematode-effective Bt gene. The toxic crystal molecules coded by the Bt gene are large; they range in molecular mass from 40 to >70 kDa (Wei et al, 2003). Crystals would need to be ingested by the plant-feeding nematode and there has been some speculation that stylet-aperture exclusion would be a problem. However, Meloidogyne incognita, Globodera rostochiensis and Rotylenchulus reniformis are able to ingest green flourescent protein molecules of >28 kDa size from plant cells (Goverse et al, 1998; Urwin et al, 1997; Urwin et al, 2000). The size of the Bt crystal is 40-70 kDa and there is currently no evidence to suggest that crystals of that size would be excluded by the stylet aperture. The inability of Heterodera schachtii to digest proteins >40 kDa has been attributed to the a zone of exclusion established in the cytoplasm when these nematodes feed in plant cells (Bockenhoff and Grundler, 1994; Urwin, et al, 1997).
Researchers at the University of California attempted to obtain the nematode-effective Bt gene from Monsanto for development of transgenic walnut rootstocks. However, the walnut nursery market was considered too small by industry to justify costs of development. Research efforts have been focused on large-acreage crops but the Monsanto Corp. abandoned this approach for lesion nematodes in cotton in the late 1990s.
Other potential transgenic approaches: Chitinase
genes (only effective against eggs?)- Dr. Gale McGranahan, (Pomology, UC Davis).
Snowdrop lectin - Dr. Dandekar (Pomology, UC Davis)
Studies with trichosanthin (ribosome inhibiting protein).
For a list of plant species or cultivars (if any) reported to be immune or to have some level of resistance to this nematode species, copy the name
select Nemabase Resistance Search and paste the name in the Genus and species box
Suggested Alternatives to Methyl Bromide for Replanting Walnut Orchards Infested with Pratylenchus vulnus
M.V. McKenry - Seminar at UC Davis, 4/26/2004
|1.||1,3-dichloropropene at 33gpa applied deep with 110 lb/acre metamsodium applied at soil surface if soil moisture < 12%.|
|2.||1,3-dichloropropene at 50-67gpa applied deep if soil moisture > 12%.|
|3.||330 lb/acre metamsodium applied with 6-8 inches water; requires Garlon application to trunks to kill old roots.|
|4.||Dry and deep rip the soil then apply chloropicrin at 250-350 lbs per acre at 28 inches depth and 1,3-dichloropropene at 33gpa applied at 20 inches depth.|
|5.||Apply Garlon to walnut trunks to kill roots and resident nematodes, remove old roots and wait one year.|
|6.||Fallow soil for up to five years.|
Bockenhoff, A. and F.M.W. Grundler. 1994. Studies on the nutrient uptake by the beet cyst nematode Heterodera schachtii by in situ microinjection of fluorescent probes into the feeding structures in Arabidopsis thaliana. Parasitology, 109: 249-255.
Goverse, A., et al. 1998. In planta monitoring of the activity of two constitutive promoters, CaMV 35S and TR2', in developing feeding cells induced by Globodera rostochiensis using green fluorescent protein in combination with confocal laser scanning microscopy. Physiological & Molecular Plant Pathology, 52:275-284.
Raski, D.J. 1986 Plant-parasitic nematodes that attack grapes. Pp 43-57 in Anon. Plant-parasitic nematodes of bananas, citrus, coffee, grapes and tobacco. Union Carbide Corp.
Urwin, P.E., et al. 1997. Continual green-fluorescent protein monitoring of cauliflower mosaic virus 35S promoter activity in nematode-induced feeding cells in Arabidopsis thaliana. Mol Plant Microbe Interact, 10:394-400.
Urwin, P.E., et al. 2000. Transgenic resistance to the nematode Rotylenchulus reniformis conferred by Arabidopsis thaliana plants expressing proteinase inhibitors. Molecular Breeding, 6:257-264.
Wei, J-Z., K. Hale, L. Carta, E. Platzer, C. Wong, S-C Fang, and R.V. Aroian. 2003. Bacillus thuringiensis crystal proteins that target nematodes. PNAS 100:2760-2765.
Zunke, U. 1990. Ectopic feeding behaviour of the root lesion nematode, Pratylenchus penetrans, on root hairs of different host plants. Revue Nematol. 13:331-337.