Soybean cyst nematode

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Soybean cyst nematode
Soybean cyst nematode and egg

Soybean cyst nematode and egg

Systematics
Trunk : Roundworms (Nematoda)
Class : Secernentea
Order : Tylenchida
Family : Heteroderidae
Genre : Heterodera
Type : Soybean cyst nematode
Scientific name
Heterodera glycines
( Ichinohe , 1952)

The soybean cyst nematode ( Heterodera glycines Ichinohe), and soybean cyst nematode or Sojabohnenzystenälchen ( English soybean cyst nematode , abbreviated SCN ), a nematode of just under half a millimeter length (in the second growth phase J2). It attacks the roots of the soybean . The nematode is a globally important pest that was discovered in 1952.

biology

Heterodera glycines is bisexual; the two sexes have different shapes ( sexual dimorphism ). While the males are worm-shaped, the females in their adult phase develop an elongated shape that is reminiscent of an egg. Overall, the roundworm has several phases of life.

In the female body, there are eggs inside cysts . After the death of the females, the first juvenile stages ( J1 ) ripen in the fertilized eggs . Under suitable conditions (soil moisture, soil temperature, soil aeration and activating root excretions) the larvae hatch ( J2 ) and leave the lemon-shaped brown cyst envelope. They migrate to the roots of the host plant , where the 375-540 micrometer long larvae penetrate the plant tissue of the roots with the help of a 22-24 micrometer long mouth prick  . They are only able to penetrate in the second juvenile stage. In the central cylinder of the root, the nematode larva releases saliva into a single cell of the plant. The cell reacts with a local breakdown of the cell wall and, through cell division induced by the parasite , fuses with the neighboring cells to form a syncytium , from which the larva takes all of its food for its development. In doing so, she becomes sessile .

The larvae develop into adult males and females through two further stages ( J3 , J4 ). Under favorable conditions (20–24 ° C), the entire development cycle usually lasts 20–25 days. Female nematodes swell so much that their abdomen breaks out of the root and becomes visible to the naked eye. Adult males take on a worm-like shape and leave the root to find and fertilize the much larger nematode females.

After fertilization, the female continues to feed and eventually lays 200 to 400 eggs in a yellow gelatinous matrix that forms an egg sac that remains in the nematode. After the female has died, the hydroskeleton , the cuticle , hardens and turns into a cyst in which the larvae, which are dormant in the egg shell, are located. In this way, up to three generations of the parasite can arise per year.

Outside the growing season from autumn or under unfavorable environmental conditions, the larvae contained in the cysts can survive in the soil for several years. Although soybean is the main host plant, other legumes can serve as hosts as well.

infection

The infection causes several symptoms. In addition to the chlorosis of leaves and stems, root necrosis , a loss in seed yield and a suppression of root formation can occur, which is noticeable in the disturbed growth of the plant.

The symptoms above ground are not always clearly due to an infection with the nematode species; it can also be a lack of nutrients, especially a lack of iron, stress from drought, damage from herbicides or other plant diseases. The first signs of infection are groups of plants with yellow leaves. These are due to the slowed growth of the roots and an undersupply of water and nutrients.

The pathogenesis may also be difficult as stunted roots can also be a common symptom of stress or other plant diseases and pests. Only a laboratory examination or the sighting of cysts on the roots that arise from the adult female nematodes is the only way to prove an infestation by Heterodera glycines .

distribution

Segment of an infected root: Signs of infection are white to brown cysts that are filled with eggs from the parasite.

The soybean cyst nematode is believed to originate from China . It was discovered in Japan in 1952 and North Carolina in the United States in 1955 . Since the 1990s, the main soybean growing areas worldwide have been affected except in Europe (where it is also found) and Oceania.

  • Africa : Egypt
  • Asia: Iran (Golestan, Mazandaran), China (Hebei, Hubei, Heilongjiang, Henan, Jiangsu, Liaoning), Indonesia (Java), Korean Peninsula, Japan, Taiwan (unconfirmed), Russia (Amur region in the Far East).
  • North America : Canada (Ontario), USA (Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Michigan, Mississippi, Missouri, Nebraska, New Jersey, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Virginia, and Wisconsin).
  • South America : Argentina (unconfirmed), Brazil (unconfirmed), Chile, Colombia, Ecuador.

Since the 1950s, the parasite has reduced yields by up to 75 percent in the United States alone and has lost an average of $ 500 million annually. The pest causes similar problems in the soy-growing areas of South America and Asia.

Biological control

Various cultivation techniques are used to limit the damage, for example a rotation of the crop rotation during cultivation or the use of resistant varieties. Because the soybean cyst nematode is an obligate parasite and requires a live host, changing crop rotation with non-host crops such as corn can reduce or disrupt its spread.

Plants that are already stressed are more prone to infection. Therefore, cultivation techniques that maintain soil fertility are important. The basicity (pH value) and the moisture of the soil can also influence the possibility and severity of an infection. Chemical treatment with nematicides is usually not used as the negative economic and ecological consequences outweigh the above.

In 2003 and 2007, researchers at the Julius Kühn Institute (JKI) in Münster, in collaboration with the agricultural group Syngenta, investigated the influence of suppressive soils on the occurrence of the soybean cyst nematode, which often affects plants infected with the fungus Fusarium virguliforme are. The fungus leads to the "Sudden Death Syndrome" (SDS), which manifests itself in an acute death of the soybean plants. According to the study, certain soils develop self-healing powers against specific harmful pathogens and, as the study suspects, against pathogen complexes over time.

The results of the field experiments carried out in the US state of Indiana were presented in the journal Phytopathology in July 2011.

Web links

credentials

Single receipts

  1. ↑ a b c d e f g h i j k Qing Yu: Soybean cyst nematode (Heterodera glycines Ichinohe). In: Hany El-Sherny: Soybean Physiology and Biochemistry , In Tech, 2011, ISBN 978-953-307-534-1 , Chapter 22, pp. 461-474.
  2. ^ J. Herbert Waite: The phylogeny and chemical diversity of quinone-tanned glues and varnishes. In: Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 97, No. 1, 1990, pp. 19-29, doi : 10.1016 / 0305-0491 (90) 90172-P .
  3. ↑ Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries: Pests: Heterodera glycines Ichinohe - Soybean Cyst Nematode
  4. ^ Cooperative State Research, Education, and Extension Service United States Department of Agriculture. 2000. Keeping the Profits in Soybeans
  5. ↑ Julius Kühn Institute: How the soil helps itself with illnesses  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , July 28, 2011@1@ 2Template: Toter Link / www.jki.bund.de  
  6. ^ Andreas Westphal, Lijuan Xing, Soil Suppressiveness Against the Disease Complex of the Soybean Cyst Nematode and Sudden Death Syndrome of Soybean. In: Phytopathology. 101, 2011, p. 878, doi : 10.1094 / PHYTO-09-10-0245 .
  7. ↑ Topagrar.com: Self-healing powers of soils also have an effect on pathogen complexes , August 4, 2011