Plant Pathology MCQ Question and Answer | Agriculture MCQ Question

Clubroot of crucifers is favoured by soil pH 5.7.
Clubroot of Crucifers is a fungal disease that affects several plants in the cabbage family including cabbages, radishes, mustard and ornamentals such as candytuft.
It is caused by the fungus Plasmodiophora brassicae and gets its name from the club-like roots it induces in infected plants.
Warm soil (20° - 24°C), high soil moisture and acid soil (pH less than 6.5) are environmental factors that favour infection and severe disease development.

Di-ammonium phosphate contains 46% P₂O₅.
Di-ammonium Phosphate popularly known as DAP is a preferred fertilizer in India because it contains both Nitrogen and Phosphorus which are primary macro-nutrients and part of 18 essential plant nutrients.
DAP (NH₄)₂HPO₄: Fertilizer grade DAP Contains 18% Nitrogen and 46% Phosphorus (P₂O₅).

Witche's broom occurs in Tobacco.
Witches'-brooms are caused by several factors, including infection by fungi or phytoplasmas, an infestation of mites or dwarf mistletoe, genetic mutations, or adverse environmental conditions that kill the terminal bud of shoots.
The symptoms of tobacco witches broom are numerous basal and axillary branches; dwarfed, spindling branches; dwarfed leaves with general or marginal flavescence, white leaves with green veins and brown, necrotic spots, abnormal palisade cells in flavescent leaves, and dwarfed flowers on spindling pedicels.

The suitable fertilizer for the foliar spray is Urea.
Foliar fertilizers are dilute fertilizer solutions applied directly to plant leaves. As with soil application of fertilizer, the goal of foliar fertilization is to supply plants with the nutrients needed for good growth.
Urea is commonly used for foliar fertilization because of its uncharged, high solubility and it's rapid and efficiently absorbed by leaves. Once urea is absorbed, it's changed into ammonia and carbon dioxide by a chemical called urease, found in the leaves of many plants.

Algae often float on the surface of the water during the day but sink during the night due to the evolution and trapping of oxygen bubbles during the day in their photosynthesis.
Algae produce oxygen during the day during photosynthesis. The oxygen that is released gets trapped between the filaments of the algae, making it lighter and causing it to float to the top of the pond or surface of water bodies.

Chlorophyll has no functional group.
Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis.
The molecular structure of chlorophyll consists of a chlorin ring, whose four nitrogen atoms surround a central magnesium atom, and has several other attached side chains and a hydrocarbon tail formed by a phytol ester.

Gliricidia species is used as Green manure and Green leaf manure.
Gliricidia is a genus of flowering plants in the legume family, Fabaceae and tribe Robinieae. The species G. sepium is a small, deciduous, ornamental tree, cultivated and used for a variety of purposes in tropical regions.
Gliricidia is a fast-growing, nitrogen-fixing leguminous tree that is used in agroforestry to add nitrogen and organic matter to the soil.

A crop plant that can grow in nitrogen-deficient soils without an external supply of it is Cajanus cajan.
The Cajanus cajan is a perennial legume from the family Fabaceae native to the Old World. The pigeon pea is widely cultivated in tropical and semitropical regions.
Cajanus is a highly leguminous crop and can fulfill the need for nitrogen even in nitrogen-deficient soil by fixing atmospheric nitrogen itself.

Simazine from the following herbicides is derived from urea.
Simazine is a selective herbicide C₇H₁₂N₅Cl used to control weeds, especially among crop plants. It is a diamino-1,3,5-triazine that is N,N'-diethyl-1,3,5-triazine-2,4-diamine substituted by a chloro group at position 6.
It has a role as a herbicide, a xenobiotic, and an environmental contaminant. It is used to control broad-leaved weeds and annual grasses in a field, berry fruit, nuts, vegetable and ornamental crops, turfgrass, orchards and vineyards.

Tabtoxin was first isolated in pure form.
Tabtoxin, also known as wildfire toxin, is a simple monobactam phytotoxin produced by Pseudomonas syringae. It is the precursor to the antibiotic tabtoxinine β-lactam (TBL).
Tabtoxin is a dipeptide precursor to the biologically active form of TBL, differing by having an extra threonine attached by a peptide bond to the C terminus.
Tabtoxin resistance protein (TTR) is an enzyme that catalyzes the acetylation of TBL, rendering tabtoxin-producing pathogens tolerant to their phytotoxins.