Identification of new cyst nematode in soybean fields

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Identification of new cyst nematode in soybean fields

Cyst nematodes illustrate an extensive group of sedentary endoparaistic nematodes that has wide variety of species which are comprised in three important genera based on cyst shape i. e. Heterodera (lemon shaped), Globodera (round shaped) and Punctodera (pear shaped)1.

Formation of cysts is one of the important characteristics in cyst nematodes but cyst shape alone is not a promising characteristic for species identification. Female nematodes often termed as dead females because cuticle turns into leathery cyst wall in order to protect eggs inside the cysts from harsh environments such as drought.

In 2016, cyst nematode was found in soybean fields of Korea which was morphologically different from the soybean cyst nematode Heterodera glycines and named as Heterodera sojae2. Consequently, a research was conducted in order to examine Heterodera glycines (Hg), H. sojae (Hs) and H. trifolii (Ht) by microscopy. Microscopic techniques which were used to examine includes morphological (cyst shape, color, and sizes); structural (vulvar cone slope angles [VCSA], vulvar cone surface wrinkles [VCSW], and cyst wall thickness, composition and texture); and biological (fecundity [number of eggs in a cyst], hatching rate [%] and emergence [number of second-stage juveniles (j2) hatched from eggs formed in a cyst (i.e., fecundity × hatching rate)3.

It is found that all the three nematodes belong to genus Heterodera, Ht was larger in all morphological characteristics as compared to Hg and Hs. Hs showed smaller “a” value with more thickened and strengthened collagen-like texture of cyst wall than Hg and Ht. There were no significant differences in emergence among cyst nematodes due to the offset of fecundity and hatching rate; however, the inoculum potential of Hs may be not so persistent as Hg and Ht in fields because of its lower fecundity and higher hatching rate than the others.

In summation, the study of morphological, structural and biological characteristics of cysts in cysts nematodes play a paramount role in differential diagnoses and reliable management of cyst nematodes by developing efficient strategies.

References:

  1. Golden, A. M. 1986. Morphology and identification of cyst nematodes. In: Cyst nematodes, eds. by F. Lamberti and C. E. Taylor, 23-45. Springer Nature, Switzerland.
  2. Kang H., Eun G., Ha J., Kim Y., Park N., Kim D., Choi I.. 2016; New cyst nematode,Heterodera sojae sp. (Nematoda: Heteroderidae) from soybean in Korea. J. Nematol. 48: 280-289.
  3. Han, G. R., Kang, H., Choi, I. S., Kim, D., Yun, H. Y. and Kim, Y. H. 2020. Differential Morphological, Structural and Biological Characteristics of Cysts in Heterodera Species in Korea. Plant Pathol. J. 36(6): 628-636 (2020).

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