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Cyst Nematodes Are Thought to Have Evolved the Sedentary Lifestyle Independently

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Cyst Nematodes Are Thought to Have Evolved the Sedentary Lifestyle Independently Cyst nematodes are thought to have evolved the sedentary lifestyle independently. They spend most of their active lives within plant roots, feeding on greatly modified host cells. Cyst nematodes represent a large group of plant parasites comprising 75 or more species. Heterodera Etymology Globodera Punctodera Heterodera Cactodera heteros = other, different Dolichodera deras = skin, body wall Afenestra Globodera Brevicephalodera globus = round deras = skin, body wall Cereal cyst nematode Heterodera avenae Soybean cyst nematode H. glycines Pigeon pea cyst nematode H. cajani Maize cyst nematode H. zeae Clover cyst nematode H. trifolii Brassica cyst nematode H. cruciferae Potato cyst nematode . Globodera rostechiensis 1859 – First report of a cyst nematode from Germany, as causal organism of “Rubenmuditkeit” (Beet tiredness) 1871 – Schmidt named it Heterodera schachtii . Other forms of cyst nematodes discovered on pea, potato, cereals - mostly in Germany 1940 – Franklin separated five species . H. schachtii, H. goettingiana, H. rostochiensis, H. major, H. punctata Round cysts transferred to Globodera Heterodera . Mature female and Cyst ▪ Lemon-shaped with short neck and terminal cone (vulval cone), turning into a hard wall, brown or black in colour, vulva terminal, anus dorsally sub-terminal, vulval fenestration present, ambifenestrate or bifenestrate, underbridge and bullae often present, most eggs retained inside the body, some may be laid in gelatinous matrix . Male ▪ About 1 mm, vermiform, stylet and oesophagus well-developed, tail end twisted, without bursa, spicules robust, gubernaculum simple. Second-stage juvenile ▪ Body slender, about 400-500 µm long, cephalic sclerotisation and stylet robust than in root-knot nematode, oesophageal glands overlap intestine ventrally, tail with a prominent hyaline portion Signs Lemon Bodies Cysts on Roots More Cysts Domain: Eukaryota Kingdom: Metazoa Phylum: Nematoda Class: Secernentea Order: Tylenchida Family: Heteroderidae Genus: Heterodera spp. Sedentary endoparasite Cyst containing eggs remain in soil during off-season Mostly hatching occurs in response to host root exudates Infective stage – Second-stage juvenile Prefer meristematic zone for penetration Establish special feeding areas (Syncytia) in vascular tissues Further grow to adults, body changes from vermiform to lemon-shaped gradually, posterior part emerges out of root Adult males become vermiform, are coiled inside J4 cuticle, and finally come out into soil after rupturing cuticle. Females lay eggs inside their body, turn brown (cyst) and fall into the soil Major differences from Root- knot nematode No spike tailed stages Stylet present in J3 and J4 Posterior portions of J4 and females protrude out of roots Reproduction usually sexual Egg laying inside the body of female Female forms cyst after egg laying J2 become sedentary after penetration, head located near vascular tissues Enzymatic secretions lead to the formation of syncytia Syncytium involves xylem, phloem, pericycle, endodermis Partial cell wall dissolution takes place to result in a big multicellular cytoplasmic mass (syncytium) First report from Germany by Kuhn in 1874 Nomenclature changed from Heterodera schachtii – . H. schachtii subsp. major – H. major – H. avenae (Wollenweber, 1924) First report from India by Vasudeva in 1958 from Rajasthan Distribution • Europe, Australia, Russian states, India, Pakistan . India ▪ • Rajasthan, Haryana, Delhi, Himachal Pradesh, Jammu & Kashmir, Madhya Pradesh, Punjab, Uttar Pradesh Hosts . Wheat, Barley (Molya disease) . Oats Lemon-shaped cyst, each containing ca. 400 eggs formed during march/April, remain dormant in soil till November/December Hatching coincides with wheat sowing (Nov/Dec) at 16-18 C Root exudates do not play any role in hatching Only 50% eggs hatch in first year White females can be seen on roots during Jan/Feb Stunted growth in patches Chlorosis when crop is 1-2 months old Reduced tillering Culms become thinner and weaker Earheads fewer and bear fewer grains Roots become bushy, having swellings at the sites of penetration White glistening females appear during Jan/Feb on the swellings Maize cyst Nematode, Heterodera zeae . 1st reoprted from India in 1971. Prevelent through the country in maiz producing areas. Rice Cyst Nematode , Heterodera oryzicola . 1st reported from India in 1978. Restricted in the area of Goa and Kerala. Sugarbeet Cyst Nematode : Heterodera hachachetii Alfalfa cyst nematode : Heterodera medicaginis Tobacco Cyst Nematode : Heterodera tabacum Barley Cyst Nematode : Heterodera filipjevi Pearl cyst Nematode : Heterodera gambiensis Pea Cyst Nematode : Heterodera goettingiana Chick Pea Cyst Nematode : Heterodera rosii Lentil Cyst Nematode : Heterodera ciceri Sugarcane Cyst Nematode : Heterodera sacchari Cacti Cyst Nematode: Heterodera cacti Pegion Pea Cyst Nematode : Heterodera cajani Preferred Scientific Name . Globodera rostochiensis (Wollenweber, 1923) Skarbilovich, 1959 Preferred Common Name . yellow potato cyst nematode Denmark: kartoffelal; kartottelcystenematod Finland: peruna-ankeroinen Germany: Aelchen, Goldfarbenes Kartoffelzysten-; Aelchen, Kartoffel-; Nematode, Kartoffel- Iran: nematode sibsamini Italy: Anguillula della patata Netherlands: Aardappel cystenaaltje Norway: potetcystenematode Sweden: potatiscystnematod Domain: Eukaryota Kingdom: Metazoa Phylum: Nematoda Class: Secernentea Order: Tylenchida Family: Heteroderidae Genus: Globodera Species: rostochiensis Globodera . Mature female & Cyst ▪ Spherical with a short neck, terminal portion not forming a cone, vulva terminal, vulval fenestra circumfenestrate, underbridge, bullae rarely present, anus dorsally sub- terminal, no anal fenestra . Male & Second stage juvenile ▪ As in Heterodera 1.They are 1mm long roundworm belonging to genus Globodera, comprising around 12 species. • They live on plants of Solanaceae family(e.g., Potato, Tomato). Potato Cyst Nematode(Eel Worms) They are 1mm long roundworm belonging to genus Globodera, comprising around 12 species. The major hosts of G. rostochiensis are restricted to the Solanaceae, in particular potato, tomato and aubergine. A number of weeds in the Solanaceae are also hosts. Datura tatula, Physochlaina orientalis, Saracha jaltomata etc. Eggs of Eel nematode hatch in presence of Solanoeclepine-A. This is secreted by roots of solanaceous plants and hence the larva establishes a feeding site G. rostochiensis is a world wide pest of temperate areas, including both temperate countries and temperate regions of tropical countries, . for example India’s Nigrilis region. PCN is considered to have originated from the Andes region of South America, from where it spread to Europe with potatoes. The cyst which adheres to host roots, tubers and to soil particles during transportation gives rise to new infestations. Cysts are also successfully spread by wind dispersal, sand storms too. Rain which causes flooding and water to run off fields into trenches or irrigation channels also redistributes cysts into adjoining areas. Eggs: . Eggs of G. rostochiensis are always retained within the cyst body and no egg sacs are produced. The eggshell surface is smooth and no microvilli are present. Females: . Females emerge from the root cortex about one month to six weeks after invasion by the second-stage juveniles. They are pure white initially, turning golden yellow on maturation. Mature females are approximately 500 µm in circumference without a cone. The cuticle of the female sometimes has a thin subcrystalline layer. Head bears one to two annules and the neck region has numerous tubercules and head skeleton is hexaradiate and weak. Stylet is divided equally in length between the conus and the shaft. Important diagnostic feature is the backward slope of the stylet knobs. Cyst: . Cysts contain the eggs, the progeny for the next generation, and are formed from the hardened dead cuticle of the female. Newly produced cysts may still show an intact vulval basin but older cysts, particularly those which have been in the soil for many seasons, lost all signs of their genitalia with only a hole in the cuticle to show the position of the fenestral basin. Males: . The male is vermiform in shape with a short tail and no bursa. On fixation, the body assumes a curved shape with the posterior region twisted at a 90 degree angle to the remainder of the body. There are four incisures in the mid-body i.e. three bands which terminate on the tail. The rounded head is offset and bears 6-7 annules. The head is strongly developed having a hexaradiate skeleton. The cephalids are located at body annules 2-4 and 6-9, respectively. The single testis fills half the body cavity. The paired spicules are arcuate and end with single tips. The gubernaculum is around 10 µm in length and 2 µm in thickness and lies in a position dorsal to the spicules. Juveniles: . 2nd-stage juvenile hatches from the egg, the first moult taking place within the egg. Juvenile, like the male, is vermiform with a rounded head and finely tapered tail. Hyaline portion of the tail represents about two thirds of its length. Lateral field has four incisures in the mid-body region reducing to three at the tail terminus and anterior end. Head is slightly offset and bears four to six annules and head skeleton is well developed and hexaradiate in form. Cephalids are located at body annules 2-3 and 6-8, respectively. Stylet is strong, the conus being about 45% of the total
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