Pratylenchus scribneri

Classification:

       Chromadorea
       Rhabditida
       Tylenchina
        Tylenchoidea
         Pratylenchidae
          Pratylenchinae

Pratylenchus scribneri Steiner, 1943

Scribner's Root Lesion Nematode

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Morphology and Anatomy:

Female Anterior:

Strong head frame, flattened lip region.

Ventral overlap of esophageal glands over intestine.

Female Posterior:

Monovarial, prodelphic; short post-uterine sac.

Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

Distribution:

Africa: Cameroon, Asia: China, Pakistan, Turkey, Europe: Italy, North America: United States (widespread in 35 states) Readily distributed in tooted plant material (Scheck, 2022).

Males not present, not sexually reproducing. Roman and Triantaphyllou (1969) determined that there are two reproductive forms in the species; one has n=6 chromosomes and reproduces by meiotic parthenogenesis, the other has a somatic chromosome number of about 25 and reproduces by mitotic parthenogenesis.

In meiotic parthenogenesis there is no fertilization of oocytes and a meiotic reduction division of the unfertilized egg cell; the diploid number of chromosomes is re-established by fusion with the nucleus of a polar body,

In mitotic parthenogenesis there is no fertilization and there is mitotic division of oogonia so that the somatic number of chromosomes is preserved throughout.

Damage:

Plates A and B. Young roots; (a) lesions with single nematodes, (b) 3-6 nematodes, (c) up to 50 nematodes, and (d) areas with no nematodes.
Plates C and D. Older roots; (a) with coalesced lesions containing numerous nematodes and eggs, and (b) necrotic areas with few nematodes but numerous eggs.
Lesion development on soybean roots after 45 days exposure to P. scribneri. From Acosta and Malek (1981).

Infected roots have initial symptoms of small, water-soaked lesions that soon turn brown to black. Black lesions are formed along the root axis and may coalesce laterally to girdle the roots. Infected plants have fewer feeder roots, resulting in stunted root growth. Top growth may exhibit general symptoms of an impaired root system including lack of vigor, dieback, chlorotic and small leaves, and reduction of yield.

In general, root lesion infection results in plants exhibiting symptoms of chlorosis, wilting, and stunting.Affected root tissue may slough off leaving a severely reduced root system. Secondary infection by fungi and bacteria may further destroy the root system by causing sloughing off of the root tissues and rot (Chitambar et al, 2018, Scheck, 2022).

Pratylenchus scribneri is an economic pathogen causing damage to the roots and loss of yield to a wide range of crops, including barley, maize, soybean, potato, sugar beet, broccoli, tomato, onion, strawberry, and peach (Castillo and Volvas 2007). It reduces the yield and quality of potato tubers (Orlando et al., 2020).

Management:

References:

Acosta, N. and R. B. Malek (1981). Symptomatology and histopathology of soybean roots infected by Pratylenchus scribneri and P. alleni. J. Nematol. 13:6-12.

Castillo, P., and Volvas, N. 2007. Pratylenchus (Nematoda: Pratylenchidae): Diagnosis, Biology, Pathogenicity and Management. Nematology Monographs and Perspectives, Vol. 6. Brill, Leiden, The Netherlands.

Chitambar, J. J., Westerdahl, B. B., and Subbotin, S. A. 2018. Plant Parasitic Nematodes in California Agriculture. In Subbotin, S., Chitambar J., (eds) Plant Parasitic Nematodes in Sustainable Agriculture of North America. Sustainability in Plant and Crop Protection. Springer, Cham.

Orlando, V., Grove, I.G., Edwards, S.G., Prior, T., Roberts, D., Neilson, R. and Back, M., 2020. Root‐lesion nematodes of potato: current status of diagnostics, pathogenicity and management. Plant Pathology, 69(3), pp.405-417.

Roman, J., Triantaphyllou, A.C. 1969. Gametogenesis oand reproduction of seven species of Pratylenchus. J. Nematology 1:357-362.

Scheck, H.J. 2022. California Pest Rating Proposal for Pratylenchus scribneri Steiner, 1943 Scribnerï¿½s root-lesion nematode CDFA, Sanramento, California'