''Nacobbus'' is a genus of plant-parasitic

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. Prevalent in North and South America, the genus Nacobbus threatens crops such as tomato, potato,

quinoa Quinoa (''Chenopodium quinoa''; , from Quechuan languages, Quechua ' or ') is a flowering plant in the Amaranthaceae, amaranth family. It is a herbaceous annual plant grown as a crop primarily for its edible seeds; the seeds are high in prote ...

and

sugarbeet A sugar beet is a plant whose root contains a high concentration of sucrose and that is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together with ...

. They can cause so much damage that they are considered to be of

quarantine A quarantine is a restriction on the movement of people, animals, and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have bee ...

importance. 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, ...

and biology of ''Nacobbus'' is not all that well known, although it is possible that the host—in this case, a specific crop—influences how the morphological characteristics of these nematodes are expressed. __TOC__

Taxonomy

Two type species of ''Nacobbus'', ''

Nacobbus aberrans ''Nacobbus aberrans'' is a plant pathogenic nematode. References External links Tylenchida Lettuce diseases Vegetable diseases Agricultural pest nematodes {{Secernentea-stub ...

'' and ''

Nacobbus dorsalis ''Nacobbus dorsalis'', the false root-knot nematode,) is a plant pathogenic nematode. References Tylenchida Plant pathogenic nematodes {{Secernentea-stub ...

'', were identified in 1944 by Thorne and Allen along with two additional possible species, ''N. batatiformis'' and ''N. serendipiticus''. In 1970, Sher classified ''N. batatiformis'' and ''N. serendipiticus'' under the species ''Nacobbus aberrans''. ''N. aberrans'' and ''N. dorsalis'' were concluded to be the only two species of ''Nacobbus'' and were differentiated by morphological characteristics. Today, the classification of ''Nacobbus'' into these two species is generally accepted as accurate. However, recent studies focused on morphology and host-range suggest that this classification may need to be reevaluated. Proper classification of the genus is crucial in order to most effectively manage and quarantine them.

Life cycle

In terms of feeding strategy, ''Nacobbus'' is classified as a false root-knot

because it is both migratory

endoparasitic 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 ...

and sedentary endoparasitic. It is the only known nematode to do so; all others employ either one strategy or the other. In'' Nacobbus'', each strategy is employed at different stages in the life cycle. Immature males and females are migratory whereas mature females are sedentary. The life cycle of ''Nacobbus'' begins when they hatch from eggs in the soil and migrate through roots and soil until mature, causing

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 ...

lesions. Then, mature females form a feeding site called a

syncytium A syncytium (; : syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell that can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), i ...

, which is composed of plant material and formed in healthy root tissue. There the females produce eggs and lay them in the soil to hatch.

References

{{Authority control Secernentea genera Tylenchida Plant pathogenic nematodes