Anguina tritici is the parasitic nematode found on ______ plant.

Question

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Correct — option (1), Wheat. The answer is written into the organism's own name. Under the binomial system every species carries two names, a genus and a specific epithet, and the epithet here is tritici, the genitive of Triticum, which is the botanical genus of wheat. Anguina tritici therefore means, quite literally, the little eel of wheat, and a candidate who has learnt to read the second half of a scientific name can answer this question without ever having met the organism. The biology bears the name out. Anguina tritici is the wheat seed gall nematode, a roundworm that carries out its whole cycle on wheat. Its juveniles survive for years, dried and dormant, inside hard blackish galls that have replaced normal grains in the ear. When such a gall is sown along with the seed and meets moisture in the soil, the juveniles revive, move up the outside of the young shoot in a film of water, and enter the growing point. There they live among the developing floral parts, and when the ear forms the nematode's presence turns individual grains into galls in place of seed, which is the disease called ear cockle. Each gall is packed with thousands of juveniles, and the cycle resumes when those galls are harvested and sown again with the next crop. The same nematode also carries the bacterium Rathayibacter tritici into the ear, and the two together produce the yellow slime or tundu disease of wheat, in which a sticky yellow ooze appears on the ear head. The species has a further claim on a student's memory: described by Needham in 1743 from galls in English wheat, it was the first plant-parasitic nematode ever recorded, which is why it turns up so often in examinations. None of the other three crops printed is its host, so option (1) is the answer.

Why the other options are wrong — (b) Rice is the most plausible of the three wrong crops, because rice does have well-known nematode diseases of its own and a candidate who remembers that nematodes attack cereals may pick the cereal that comes to mind first. But the nematodes of rice are different species with different names: Aphelenchoides besseyi causes the white tip disease of rice, and Ditylenchus angustus causes ufra. Neither is Anguina tritici, and the specific epithet tritici could not point to rice in any case, since rice belongs to the genus Oryza. The general lesson is worth more than the particular fact: when a question gives you a full binomial, read the second word before you read the options, because it very often names the host, the place of discovery or the distinguishing feature.  (c) Jowar, or sorghum, is an important dryland cereal in Maharashtra, which is precisely why it is printed here — the Commission fills the option set with crops the candidate knows well from the state's cropping pattern so that familiarity alone cannot decide the answer. Sorghum is Sorghum bicolor, and nothing in the name Anguina tritici points to it. The field problems of jowar that MPSC does ask about are chiefly fungal, grain smut and downy mildew among them, rather than this nematode. Choosing a crop because it is locally important, rather than because the name in the stem leads to it, is the error this option is designed to catch.  (d) Bajra, or pearl millet, is Pennisetum glaucum, another staple dryland cereal of Maharashtra, and it is included for the same reason as jowar: to make the option set a list of four familiar grains among which only the scientific name can discriminate. The diseases of bajra that appear in examinations are downy mildew, known as green ear disease, and ergot, both of them caused by fungi rather than by a nematode. There is nothing in the stem that would lead a reader towards pearl millet, and the epithet tritici positively leads away from it.

Concept: Nematodes are unsegmented roundworms of the phylum Nematoda, and while most are free-living in soil and water, a large group are obligate parasites of plants. They feed with a hollow protrusible mouth spear, the stylet, which they push into a plant cell to withdraw its contents, and they are classified by where they do it: ectoparasites feed from outside the root, endoparasites enter the tissue, and among the endoparasites some migrate through the plant while others settle at a permanent feeding site. The genus Anguina belongs to the seed-gall group, which is unusual in attacking the flower and seed rather than the root: the nematode rides the growing point upwards, reaches the developing ear, and diverts the plant into producing a gall in place of a grain. This gives the group a remarkable survival strategy, since the dried gall lets juveniles remain dormant and viable for years and travels with the seed lot into the next season, so the disease spreads with the farmer's own sowing rather than through the soil. Two other plant-parasitic nematodes worth holding alongside it are the root-knot nematodes of the genus Meloidogyne, which raise galls on roots, and the cyst nematodes of Heterodera and Globodera, whose females harden into protective cysts.

State PCS 2023 Q43 — Science & Technology PYQ with Answer

State PCS 2023 Q43 — Science & Technology PYQ with Answer