Globodera tabacum, commonly known as a tobacco cyst nematode, is a plant parasitic nematode that mainly infests the tobacco plant, but also plants in Solanaceae

Solanaceae

Solanaceae are a family of flowering plants that include a number of important agricultural crops as well as many toxic plants. The name of the family comes from the Latin Solanum "the nightshade plant", but the further etymology of that word is unclear...

 family.

History and significance

The tobacco cyst nematode, Globodera tabacum, is a serious and important soil borne parasite of the shade and broadleaf tobacco. The most important host plant for this nematode is tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

 (Nicotiana tabacum L), but other hosts include tomato

Tomato

The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

, eggplant and closely related solanaceous weeds.
This species of nematodes was first discovered in Hazardville, Connecticut in the 1950s. Nematode infection of the tobacco root system causes dramatic stunting, yield loss and decreases leaf quality.

Distribution

Globodera subspecies are distributed as follows (older data):
Globodera tabacum tabacum – Connecticut

Connecticut

Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...

 and Massachusetts

Massachusetts

The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

. Globodera tabacum solanacearum - Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

 and North Carolina

North Carolina

North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...

. Globodera tabacum virginiae – Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

, Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 and Central America

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

. As of 1998, Globodera tabacum tabacum has been reported in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 as well.

Morphology

Head has four head annules, lip region is well developed, oral disk is present and the entire head region is heavily sclerotized. The stylet has three rounded knobs while tail is pointy and rounded at the very tip. There are total of six lips, four large and two small.

Host – parasite relationship

The tobacco cyst nematode is a sedentary semi-endoparasite of the roots. Its feeding site and feeding patterns are typical of the genus Globodera. Nurse cell is a multinucleate syncytium.
Tobacco cyst nematode causes significant damage on tobacco root system mainly by intracellular migration

Cell migration

Cell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations...

. This damage is caused both by mechanical penetration as well as with the enzyme secretions. Syncytium

Syncytium

In biology, a syncytium is a large cell-like structure; filled with cytoplasm and containing many nuclei. Most cells in eukaryotic organisms have a single nucleus; syncytia are specialized forms used by various organisms.The term may also refer to cells that are connected by specialized membrane...

 is formed in pericycle and endodermal cells of the plant. Unlike root-knot nematodes, the tobacco cyst nematode does not form feeding tubes enveloped in an endoplasmatic reticulum. Due to lack of enzymes that cause hypetrophy and hyperplasia, there is no galling observed.

Life cycle/ Reproduction

The life cycle is typical of plant parasitic nematodes. This means that Globodera tabacum nematode has four juvenile stages, molts four times and then finally reaches adult stage. The duration of its life cycle is speculated to be temperature dependent. Hatching is often initiated by root exudate.

Taxonomy

Even though there are some disagreements among scientists on Globodera tacabum taxonomy, it is believed that this complex consists of three subspecies: subspecies solanacearum, subspecies tabacum and subspecies virginae. Mugniéry et al. (1992) confirmed hybridization between all three entities but these groups vary greatly in their capacity to damage tobacco.

Management

Management practices consist of crop rotation

Crop rotation

Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons.Crop rotation confers various benefits to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals...

, planting resistant cultivars and general soil maintenance and hygiene. Chemical control is an option but it is not widely used in USA against Globodera tabacum spp. virginae, but only against other two subspecies. The use of 1,3 Dichloropropene as soil fumigant is in process of being phased out in EU. Using trap crop has been suggested by some authors as a possible way of controlling this nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

.