''Pratylenchus'' is a genus of

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s known commonly as lesion nematodes.Crow, W. T
Amaryllis lesion nematode, ''Pratylenchus hippeastri''.
EENY-546. University of Florida IFAS. 2012. They are

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

on plants and are responsible for root lesion disease on many taxa of host plants in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

regions around the world. Lesion nematodes are migratory endoparasites that feed and reproduce in the

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

and move around, unlike the

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

root-knot nematode Root-knot nematodes are plant-parasitic nematodes from the genus ''Meloidogyne''. They exist in soil in areas with hot climates or short winters. About 2000 species of plants worldwide are susceptible to infection by root-knot nematodes and they ...

s, which may stay in one place. They usually only feed on the cortex of the root.Lesion nematodes.
University of Illinois Extension. 1999. Species are distinguished primarily by the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

of the stylets.Norton, D. C. ''Ecology of Plant-Parasitic Nematodes''. 1978.

Hosts and symptoms

Root lesion nematodes infect a great variety of hosts. ''Pratylenchus penetrans'' alone has over 350 host plants. They include agricultural crops such as

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

potato The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...

es,

corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...

s, and

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

. The genus is found most often in corn. Signs of disease are similar in most plants and generally include

necrotic Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who is ...

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals. Types There is no de ...

s of the roots. The lesions can also be entrances for pathogenic bacteria and fungi, which produce secondary infections. Above ground the plant becomes stunted,

chlorotic In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

, and wilted, and it often dies. A crop field may be patchy as plants wither and die. Root lesion nematodes can cause significant yield losses.Barker, K. R., et al. ''Plant Nematode Interactions''. Madison: American Society of Agronomy, Inc. 1998.

Environment

''Pratylenchus'' abundance is affected by soil moisture, mineral components, temperature, aeration, organic matter, and pH. They are more common in sandy soils and land with

weed A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...

infestations.Hallmann, J., et al. (2007)
Occurrence and importance of plant-parasitic nematodes in organic farming in Germany.
''Nematology'' 9(6), 869-79. ''Pratylenchus'' can endure a wide range of environmental conditions. Moist temperate soils are ideal conditions for breeding and migrating underground, but they can persist in warm and dryer environments. In very dry conditions they are quiescent until moisture increases and plants resume growth.Agrios, G. N. ''Plant Pathology'' 5th ed. p. 852. Most lesion nematodes remain inactive when soil temperatures are below 59 °F (15 °C) and are not fully active until temperatures rise above 68 °F (20 °C).

Management

One common management option for crop-pest lesion nematodes is soil fumigation and

nematicide A nematicide is a type of chemical pesticide used to kill plant- parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a ...

s. This is not effective for all species, and can be expensive for growers.Dropkin, V. H. ''Introduction to Plant Nematology'', 2nd ed. New York: John Wiley & Sons. 1989. Water immersion is another option. Infected plants are immersed in a hot water bath for about 30 minutes, which rids them of nematodes but does not harm the plant. This method has been successful for ''P. coffeae''. Crop rotation can help control the nematode load in the soil because different plants are susceptible to different ''Pratylenchus'' species.Saxena, G. and K. G. Mukerji. ''Management of Nematode and Insect-Borne Plant Diseases''. New York: The Haworth Press. 2007. Selecting resistant plant varieties and

cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...

s can reduce nematode problems. This is currently the only option for control of ''P. vulnus'', for example.

Life cycle and pathology

Female nematodes lay single eggs in the root or in the soil. They reproduce via

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

, laying fertile eggs without fertilization. In many species, males are rare.

References

External links

''Pratylenchus hippeastri''
on the UF / IFAS Featured Creatures website. {{Authority control Soybean diseases Potato diseases Cereal diseases Secernentea genera