Plant diseases - class-X

Pusa Swarnim is a biofortified and disease-resistant variety of Brassica (mustard) specifically developed for resistance against White rust.

Protoxins-precursor of toxins.

Ring rot of potato is caused by the bacterium Clavibacter michiganensis subsp. sepedonicus. The other options listed are fungal diseases.

Blast disease of rice is caused by Pyricularia oryzae (A-4). Loose smut of wheat is caused by Ustilago nuda (B-1). Black arm of cotton is caused by Xanthomonas malvacearum (C-2). Whip smut of sugarcane is caused by Ustilago scitaminae (D-3).

Pusa Komal is a well-known variety of cowpea bred for resistance to bacterial blight.

Breeding with wild relatives is a traditional and effective method to introduce disease-resistance genes into cultivated crop varieties.

• On the basis of the symptoms of chlorosis in the leaves, a student inferred that this was due to the deficiency of nitrogen. 
• This may be correct inference only if yellowing of leaves appeared first in young leaves then in old leaves. But Chlorosis is the main symptom of nitrogen deficiency. 
• Therefore, the leaves gradually become pale or yellow. These will first appear in old leaves and then in young leaves.
• The correct option is A.

White rust of mustard is caused by the oomycete Albugo candida, characterized by white blister-like pustules and pronounced hypertrophy and deformation of infected plant parts.

The bunt of rice is not restricted to southern India; it is found in various rice-growing regions. The other statements are generally accepted facts in plant pathology.

Potato Witches broom is a phytoplasmal disease (caused by phytoplasma, formerly grouped under Mycoplasma-like organisms) characterized by excessive proliferation of shoots.

Bunt of wheat, caused by Tilletia species, produces teliospores that release trimethylamine, giving off a characteristic foul fishy odor in infested fields.

Bunchy top of banana was introduced from Sri Lanka (1), and the Potato tuber moth was introduced from Italy (2). Flag smut of wheat was not introduced from Fiji.

Nephotettix impicticeps is the known green leafhopper vector responsible for transmitting the Tungro virus disease in rice crops.

Matching the plant diseases to their pathogens: Angular leaf spot of cotton is caused by Xanthomonas malvacearum (A-4), Late blight of potato by Phytophthora infestans (B-1), Red rot of sugarcane by Colletotrichum falcatum (C-2), and Tikka leaf spot of groundnut by Cercospora personata (D-3). This corresponds to option B.

Tundu disease of wheat is a composite disease caused by a combination of the seed gall nematode (Anguina tritici) and the bacterium (Clavibacter tritici) working together as a disease complex.

Little leaf of fruit trees is a well-known physiological disorder caused by a deficiency of zinc in the soil and plant tissues. Zinc plays a crucial role in auxin synthesis, which directly affects leaf expansion and internode elongation.

Bacillus subtilis and Trichoderma viride are well-documented biological control agents used to suppress various plant pathogens.

Khaira disease of rice is classically characterized by chlorotic patches that turn brown, caused specifically by a deficiency of zinc. The other listed options correspond to different nutritional disorders or fungal pathogens, such as black heart of potato being caused by oxygen deficiency.

Kamal bunt of wheat is caused by a fungus (Tilletia indica), Fiji disease of sugarcane is caused by a virus, and purple top of potato is caused by phytoplasma (mycoplasma). Khaira disease of rice is caused by zinc deficiency, not a bacterium, making statement 2 incorrect.

Root rot of wheat is caused by fungal pathogens such as Fusarium or Rhizoctonia species, and wilt of cotton is caused by the fungus Fusarium oxysporum. Root knot of sugar-cane is typically nematode-induced, and angular leaf spot of cotton is bacterial.

Flag smut of wheat is caused by Urocystis agropyri, not Ustilago nuda tritici (which causes loose smut). Thus, this pair is incorrectly matched.

Tip burn of paddy is a physiological disorder caused by environmental factors like high temperature or water stress, not by a living microbe. In contrast, stem rot, false smut, and blast are all caused by fungal pathogens.

Blast of rice is caused by the fungus Magnaporthe oryzae, previously known as Pyricularia oryzae, rather than Ephelis oryzae. The other three pairs correctly match the disease name with its actual fungal causal organism.

Potato wart disease is famously caused by the chytrid fungus Synchytrium endobioticum, which produces characteristic wart-like outgrowths on tubers. The other choices feature mismatched symptoms or incorrect pathogen-host pairings.

Bordeaux mixture is a classic fungicide made from copper sulfate and lime. Carboxin is a systemic fungicide, while Chloropicrin is a fumigant and Mercuric chloride is a heavy metal disinfectant.

Crown gall disease, caused by Agrobacterium tumefaciens, induces uncontrolled cell division and enlargement in infected plant tissues. This abnormal cell proliferation is characterized biologically as hyperplasia and hypertrophy.

Peniophora gigantea (now Phlebiopsis gigantea) was one of the first fungi to be successfully commercialized for the biological control of root rot in conifers.

Ascobolus is coprophilous (grows on dung), Erysiphe is an ectoparasite (powdery mildew), Polyporus is lignicolous (wood-decaying), and Tilletia causes bunt disease.

The devastating Irish potato famine of the 1840s was caused by late blight of potato, an aggressive disease driven by the oomycete/fungal-like organism Phytophthora infestans. This pathogen rapidly destroyed foliage and tubers across the country.

Fungi were historically recognized first as causes of plant diseases, followed chronologically by bacteria, viruses, and mycoplasmas as microscopic techniques advanced. This establishes the sequence starting with fungi (4), then bacteria (2), viruses (1), and mycoplasmas (3).

White rust is caused by Albugo candida (a-4), yellow rust by Puccinia glumarum or striiformis (b-3), brown rust by Puccinia triticina (c-2), and black rust by Puccinia graminis (d-1). Matching these gives the sequence A-4, B-3, C-2, D-1.

Crown gall primarily affects woody dicotyledonous plants, including common fruit trees and vines such as apples, pears, and grapes. Sugarcane is a monocot and is not a typical host for crown gall tumors.

The standard sequence of fungal infection begins with spore germination to form a germ tube, followed by the swelling of its tip into an appressorium, mechanical or chemical penetration of the host cuticle, and finally the development of haustoria inside host cells.

Crown gall disease involves the transfer of T-DNA into the plant genome, which causes the plant cells to produce auxins and cytokinins, leading to excessive meristematic activity and tumor growth.

Grassy shoot disease of sugarcane is a classic phytoplasma disease, formerly known as a mycoplasma-like organism (MLO) infection. Mosaic, wilt, and ring spot of sugarcane are caused by viruses or fungi.

Red decay is the most widely recognized infection of sugarcane, caused by the growth Colletotrichum falcatum Went. 

Cucumber mosaic virus causes yellowing and mottling in Gerbera leaves. The CMV disease is described by extreme chlorotic mosaic, greening of veins on leaves, shading breaking in florets achieved with blossom disfigurements, and poor development of the sprout.

Trichoderma viride is a well-known antagonistic fungus widely utilized as a biocontrol agent against various soil-borne plant pathogenic fungi. Penicillium notatum produces antibiotics primarily used against bacteria rather than being a plant disease biocontrol agent.

In the life cycle of Puccinia graminis, the stages on the cereal host and alternate host follow a strict sequence: uredo stage (1), teleuto stage (4), basidial stage (3), pycnidial stage on the alternate host (2), and aecidial stage (5).

The historic 1840s famine in Ireland was caused by the widespread destruction of potato crops due to late blight, which is caused by the oomycete Phytophthora infestans.

Plant Growth-Promoting Rhizobacteria (PGPR) are extensively used for the biological control of soil-borne plant diseases.

Wart disease of potato is caused by Synchytrium endobioticum, a chytrid fungus. The correct scientific name should be written as two words: Synchytrium endobioticum. This pathogen causes tumor-like galls (warts) on potato tubers and is a quarantine disease in many regions. Plasmodiophora brassicae causes club root of crucifers, Spongospora subterranea causes powdery scab of potato, and Pseudomonas solanacearum causes bacterial wilt.

Turnip Mosaic Disease is caused by the Turnip Mosaic Virus (TuMV), a potyvirus belonging to family potyviridae, that infects majority of plants belonging to Cruciferae or Brasscicaceae. They virus can be transmitted through vectors - Aphids.

Black rot of crucifers is caused by Xanthomonas campestris pv. campestris a bacterial disease common to all cruciferous plants like Broccoli, cabbage, Kale etc. Infecting the stem, leaf, inflorescence and roots.

Pyricularia oryzae is a fungus that causes rice blast that results in lesions on leaves, stems, peduncles, panicles, seeds, and even roots. 

Tobacco mosaic virus (TMV) is a rod shaped virus, infecting tobacco leaves. It symptoms are mottled appearance that is patches of yellow and green, dwarfing etc. It spreads by mechanical abrasion of the infected tissue with a healthy one.

Zinc sulfate corrects the disorder of the rice plant called as Khaira disease seen in India.

Potatoes may be infected with many different viruses that can reduce tuber quality and yield. Mosaic virus of potatoes is one such disease that actually has multiple strains. Potato mosaic virus is divided into three categories. Symptoms of the different mosaic virus of potatoes may be similar, so the actual type usually can’t be identified by symptoms alone and is often just referred to as mosaic virus in potatoes. The three types of recognized mosaic virus in potatoes are Latent (Potato virus X), Mild (Potato virus A), Rugose or Common mosaic (Potato virus Y).