MPSC 2023 Prelims Paper-I · Question 43 of 100

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.

• (2)Rice — 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.
• (3)Jowar — 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.
• (4)Bajra — 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.

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.

MPSC prints a scientific name in the stem and four Marathi-belt crops in the options as a deliberate test of whether the candidate can decode a binomial rather than recall a fact. That skill generalises across the whole science and agriculture syllabus: oryzae points to rice, tritici to wheat, indica to India, sinensis to China, and the epithet very often carries the host or origin. The habit to build is to read the second word of any binomial and ask what ordinary noun is hiding inside it before touching the options. A second point this question quietly makes is about seed health. Because Anguina tritici survives inside galls that travel in the seed lot, the disease is controlled not by spraying the crop but by cleaning the seed, and the simplest method — floating the seed in brine so that the light galls rise and can be skimmed off — is exactly the sort of practical measure MPSC likes to test in its agriculture questions.

• Anguina tritici is the wheat seed gall nematode; its specific epithet is derived from Triticum, the botanical genus of wheat, so the name itself identifies the host.
• The nematode causes ear cockle disease, in which developing grains are replaced by hard dark galls packed with thousands of dormant juveniles that can remain viable for years within the dried gall.
• Together with the bacterium Rathayibacter tritici, the same nematode produces the yellow slime or tundu disease of wheat, in which a yellow bacterial ooze appears on the ear head.
• Anguina tritici was described by Needham in 1743 and is recognised as the first plant-parasitic nematode ever recorded, which is why it appears so frequently in general science questions.
• The nematodes associated with rice are different species — Aphelenchoides besseyi, which causes white tip disease, and Ditylenchus angustus, which causes ufra — and neither belongs to the genus Anguina.

• Ignoring the specific epithet in a binomial when the epithet is itself the answer, as tritici is here
• Picking rice because rice is the cereal most associated with pests and diseases in general knowledge, when its nematodes are entirely different species
• Choosing the locally important crop, jowar or bajra, on grounds of familiarity rather than on anything printed in the stem
• Assuming every nematode disease is a root disease; the seed-gall nematodes attack the developing ear and the gall replaces the grain

Scientific names arrive in MPSC papers in two shapes. The first, as here, prints the binomial in the stem and asks for the host, the disease or the group it belongs to, and can usually be cracked by translating the epithet. The second runs the other way, naming a familiar disease or crop pest and asking for the organism responsible, which needs genuine recall. Both are worth preparing with one compact list of the binomials that recur — the pests and pathogens of wheat, rice, cotton, sugarcane and the millets — held together with the disease each causes. Because the Commission draws its option sets from crops grown in Maharashtra, expect wheat, rice, jowar, bajra, cotton and sugarcane to fill the four slots regardless of the organism named.

No directly related past PYQ was found.

• practice — not a real PYQ

  The ear cockle disease, in which developing grains are replaced by hard dark galls, is caused in wheat by which of the following organisms ?

  • (a)A fungus of the genus Puccinia
  • (b)The nematode Anguina tritici
  • (c)The bacterium Xanthomonas oryzae
  • (d)A virus transmitted by aphids

  Answer(b) The nematode Anguina tritici — its juveniles ride up the growing shoot to the developing ear, where their presence turns grains into galls packed with thousands of dormant juveniles. Puccinia species cause the rusts of wheat, which are a different disease altogether, and Xanthomonas oryzae causes bacterial leaf blight of rice rather than anything in wheat.

• practice — not a real PYQ

  In the scientific name of an organism, information about the host plant or the place of origin is most often carried by which part of the name ?

  • (a)The genus name, which is written first
  • (b)The specific epithet, which is written second
  • (c)The name of the family
  • (d)The authority cited after the name

  Answer(b) The specific epithet, which is written second — epithets such as tritici from Triticum for wheat, oryzae from Oryza for rice, indica for India and sinensis for China regularly encode the host or the origin, which is why reading the second word of a binomial before looking at the options is a reliable examination habit. The genus name places the organism in a group of related species and rarely carries that information.