🍄Fungi, Algae, Viruses & Mycoplasma — Structure, Features, and Agricultural Significance

From Field to Lab — Four Groups That Shape Every Farm

Picture a wheat field in Punjab after the monsoon. The leaves are covered with orange-brown pustules — that is rust, caused by a fungus. In a nearby rice paddy, the standing water has a greenish sheen — that is blue-green algae, a natural biofertiliser fixing nitrogen for free. A tomato plant in the kitchen garden has curled, yellowing leaves — the culprit is leaf curl virus, transmitted by whiteflies. And in the neighbouring brinjal field, plants with tiny, bunched leaves signal little leaf disease, caused by mycoplasma (phytoplasma).

These four groups — fungi, algae, viruses, and mycoplasma — together account for the vast majority of crop diseases and biological processes in agriculture. Understanding their differences is essential for both farm management and competitive exams.

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Fungi — The Largest Group of Plant Pathogens

Fungi are eukaryotic, heterotrophic organisms. They cannot make their own food and depend on organic matter — either as saprophytes (feeding on dead matter) or as parasites (feeding on living hosts).

Structure and Key Features

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Algae — The Photosynthetic Microorganisms

Algae are photosynthetic microorganisms that are nutritionally Autotrophs. They are also called primary producers of organic matter because they convert sunlight into food.

Key Features

Blue-Green Algae (BGA) — A Special Case

BGA (Cyanobacteria) are unique because they are prokaryotic organisms that contain Chlorophyll — making them the only prokaryotes capable of oxygenic photosynthesis.

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Viruses — The Smallest Infectious Agents

Viruses are smaller than bacteria and are obligate intracellular parasites — they can only multiply inside living host cells. Outside a host, they exist as inert chemical particles.

Key Features

Virus Composition — A Critical Exam Table

Different types of viruses have different chemical compositions. This is one of the most frequently tested topics.

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Mycoplasma (MLO / Phytoplasma) — The Wall-less Pathogens

Mycoplasma (Mycoplasma-Like Organisms) are unique pathogens that are larger than viruses but smaller than bacteria. They cause many important yellowing diseases in plants.

Key Features

Important Mycoplasma Diseases

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Comparison Table — Fungi vs Algae vs Viruses vs Mycoplasma

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Oxidative vs Photophosphorylation

These two processes are the main ways living cells produce ATP (energy currency).

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Summary Table — Key Facts at a Glance

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Summary Cheat Sheet