Root-knot nematode (English spelling)

A general term for a genus in the class Nematoda of the phylum Peluga (Azotochoranida). A representative plant parasitic nematode, it is found worldwide, mainly in tropical regions but also in temperate zones, and parasitizes the roots of a wide range of plants, both grasses and trees. The nematode is named after the tissue where it infests, swelling and forming a nodule. The nematode's slender larvae, 0.5 mm in length, invade the roots through the epidermis, and once they settle in the tissue, they continue to grow using the tissue cells as nutrients, becoming slender male adults with a body length of about 1.5 mm, or spherical or pear-shaped female adults with a diameter of about 1 mm. The female lays 500 to 800 eggs in a gelatinous sac at the end of the tail. The roots of the host plant become covered in nodules due to the parasitism of a large number of larvae, and the roots become less functional, slowing growth and often dying. In addition, the nodules make it easy for disease bacteria to enter the plant, causing additional disease and further increasing damage. It causes damage to many crops and trees, including tomatoes, cucumbers, sweet potatoes, peanuts, tobacco, konjac, mulberry, grapes, peaches, apples, and cherries. In Japan, about five species, including M. incognita and M. hapla, are important, and one generation takes 30 to 40 days.

[Minoru Ichinohe]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

袋形(たいけい)動物門線虫綱の1属の総称。代表的な植物寄生線虫で、熱帯地方を中心に温帯にも及ぶ世界的分布を示し、草や木を問わず広範囲の植物の根に寄生し、線虫の寄生部位の組織が膨れてこぶ状になるのでこの名がある。線虫は、体長0.5ミリメートルの細長い幼虫が根の表皮から侵入し、組織内に落ち着くとその場所で組織細胞を栄養に成長を続け、体長約1.5ミリメートルの細長い雄成虫、または直径1ミリメートル内外の球形ないし洋ナシ形の雌成虫となる。雌は500～800個の卵を尾端のゼラチン質の袋に産み出す。寄主植物は、大量の幼虫の寄生で根がこぶだらけになり、根の機能低下で生育が遅れ、枯死することも少なくない。また、こぶの部分から病菌が入りやすく、病害を併発し被害をいっそう大きくする。トマト、キュウリ、サツマイモ、ラッカセイ、タバコ、コンニャク、クワ、ブドウ、モモ、リンゴ、サクラなど多くの作物や樹木に被害を及ぼす。日本では、サツマイモネコブセンチュウM. incognita、キタネコブセンチュウM. haplaなど5種ほどが重要で、1世代には30～40日を要する。

［一戸　稔］

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