Q.65 Puccinia graminis tritici is a macro-cyclic rust fungi due to presence of
A. Pycniospores
B. Aeciospores
C. Uredospores
D. Teleutospores
E. Basidiospores
Choose the correct answer from the options given below:
(A) A, B, C only
(B) A, B, C, D only
(C) B, C, D, E only
(D) A, B, C, D, E only
Puccinia graminis tritici (wheat stem rust fungus) is classified as macro-cyclic because its complete life cycle includes all five spore stages: pycnial (0), aecial (I), uredinial (II), telial (III), and basidial (IV). Micro-cyclic rusts omit some early stages. Let’s break down each spore’s role and evaluate options.
Spore Stages Overview
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A. Pycniospores (spermatia): Produced in pycnia on barberry (secondary host). Involved in plasmogamy (sexual fusion via dikaryotization).
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B. Aeciospores: Formed in aecia on barberry. Infect primary host (wheat).
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C. Uredospores: In uredia on wheat. Repeat infection on wheat (summer stage).
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D. Teleutospores (teliospores): In telia on wheat. Thick-walled, overwinter; germinate to basidia.
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E. Basidiospores: From basidia on teleutospores. Infect barberry to start cycle.
All five define the macro-cyclic nature (full heteroecious cycle on wheat-barberry).
Option Analysis
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(A) A, B, C only: Incorrect—excludes telial and basidial stages (essential for completion).
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(B) A, B, C, D only: Incorrect—misses basidiospores (initiate pycnial stage on barberry).
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(C) B, C, D, E only: Incorrect—omits pycniospores (sexual stage marker).
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(D) A, B, C, D, E only: Correct. All stages present confirm macro-cyclic life cycle.
Final Answer: (D)
Introduction to Puccinia graminis tritici Macro-Cyclic Rust Fungi
Puccinia graminis tritici macro-cyclic rust fungi causes devastating wheat stem rust, completing its full heteroecious cycle on wheat (primary host) and barberry (secondary). This NEET/CSIR NET favorite tests spore stages—pycniospores to basidiospores—defining its “macro-cyclic” status (all 5 forms vs. micro-cyclic omitting early ones).
Life Cycle Stages: Why All 5 Spores Make It Macro-Cyclic
Puccinia’s complex cycle ensures survival and spread:
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Pycnial Stage (0): Flask-shaped pycnia on barberry release pycniospores for dikaryotization.
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Aecial Stage (I): Orange aecia produce aeciospores, wind-dispersed to wheat.
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Uredinial Stage (II): Red uredospores on wheat stems cause epidemics (binucleate, repeating).
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Telial Stage (III): Black telia with teleutospores overwinter.
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Basidial Stage (IV): Teleutospores germinate basidia → 4 basidiospores infect barberry.
All stages (A-E) present = macro-cyclic.
| Stage | Spore | Host | Function |
|---|---|---|---|
| Pycnial | Pycniospores | Barberry | Sexual fusion |
| Aecial | Aeciospores | Barberry | To wheat |
| Uredinial | Uredospores | Wheat | Spread on wheat |
| Telial | Teleutospores | Wheat | Overwinter |
| Basidial | Basidiospores | Wheat/Barberry | To barberry |
Economic Impact and Control
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Damage: Yield loss up to 50% in wheat crops.
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Management: Resistant varieties (Sr genes), fungicides, barberry eradication.
Example: uredospores spread rapidly in humid fields, turning stems rusty.
Exam Tip: MCQ on Puccinia graminis tritici
Q: Macro-cyclic due to? Ans: (D) All spores. Partial lists fail—memorize sequence: 0→I→II→III→IV.
Master Puccinia graminis tritici macro-cyclic rust fungi for mycology success—draw cycles for retention!
