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Domain: Eukaryote

Phylum: Nematoda

INTRODUCTION TO PRATYLENCHUS

Nematodes part of the genus Pratylenchus are among the top three pests for crops worldwide (5); they can reduce crop yield by 7-15% (3) and cost the US $125 billion in crops (1); making them one of the most economically impacting nematodes in the world. Pratylenchus thornei is an endoparasitic nematode that can infect a wide range of host plants (1).

ANATOMY & MORPHOLOGY

Pratylenchus has a body length of 0.35-0.5 mm, they have a mouth stylet, and their bodies are mostly made of cuticle and muscle(5). Pratylenchus thornei is a species of the root-lesion nematode, they are called the root lesion nematode because of the lesion they leave on the roots of the plants they infest; they feed on the healthy tissue of plant roots. They inhabit the roots of the plant they are infecting and are polyphagous(1).

DISTRIBUTION AND HABITAT

Like most organisms P. thornei cannot live in all environments on Earth, despite their wide range of host plants; one of the factors that limits P. thornei reproduction is the temperature of the soil they inhabit(1). P. thornei are seen in corn, wheat, soybean, potatoes and other farming products.

BEHAVIOR

Root lesion nematodes have a life cycle of 3 to 8 weeks; during this life cycle they will enter two juvenile stages before they mature into adult form, they are motile during all life stages(5). They use their stylet to penetrate the cells and ingest the cytoplasm of the host plant(1),  by releasing the contents of their pharyngeal gland. The female worms of this species are slender and motile, making it hard to distinguish where the infestation is occurring because they can move in and out of root systems (6).

The female nematode lays eggs in the root of the host plant. The presence of males depends on the species of Pratylenchus, although most of the reproduction is done via parthenogenesis(1). Their cuticle protects them from the harsh environment of the soil, they have detoxification enzymes that defend against foreign substances that may enter their body, and have a fast metabolism, which excretes waste almost as soon as it is absorbed; these three factors help the nematode to survive in the soil environment where its host lives (5). Unlike sedentary endoparasitic nematodes Pratylenchus thornei do not set up feeding sites on their host plant.

DETERMINING IF P. THORNEI IS PRESENT & HOST INFESTATION

The presence of lesion on the plant root is not enough to determine that an infestation of Pratylenchus thornei is occurring because several types of nematodes leave lesions on plant root, rather a more full proof way to identify the parasite is directly discovering its presence in the soil of the plant (6). P. thornei has a wide range of host plants it can infest, but it is most damaging to wheat, reducing wheat production that yields a $38 million loss in Australia alone (2). The presence of the β-1,4 endoglucanase gene can distinguish if P. thornei is infesting a plant because this is the gene that codes for enzymes that are key in degrading the cell wall of the host plant and helps the nematode travel from plant to plant (4). Those studying the infestation of the plant and how to fight parasites infecting the plant will find this gene useful because members of the Pratylenchus genus share some of the same characteristic, but this gene will help determine if the nematode is P.thornei.

References

1“de novo analysis and functional classification of the transcriptome of the root lesion nematode, Pratylenchus thornei, after 454 GS FLX sequencing”. Paul Nicol, Reetinder Gill, John Fosu-Nyarko, Michael G.K. Jones. International journal for parasitology

2“Pratylenchus thornei populations reduce water uptake in intolerant wheat cultivars” J.P.M. Whisha,, , J.P. Thompsonb, T.G. Clewettb, J.L. Lawrencea, J. Woodb. Field crops research.

3“Gene silencing in root lesion nematodes (Pratylenchus spp.) significantly reduces reproduction in a plant host” Jo-Anne C.H. Tan, Michael G.K. Jones, John Fosu-Nyarko. Experimental Parasitology Volume 133, Issue 2, February 2013, Pages 166–178

4“The beta-l,4-endoglucanase gene is suitable for the molecular quantification of the root-lesion nematode, Pratylenchus thornei” Fouad Mokrini, Lieven Waeyenberge , Nicole Viaene ,Fouad Abbad Andaloussi and Maurice Moens

5“Molecular biology of root lesion nematodes (Pratylenchus spp.) and their interaction with host plants” M.G.K. Jones and  J. Fosu-Nyarko

6“Root-lesion Nematodes resistant rootstocks most promising method of control” M. W. Allen