Koch's postulates were based on the studies conducted on which...

Q.1

ICAR AIEEA PG 2024 - Plant Sciences (Q.57)

Assertion & Reason +4 −1

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R):

Assertion (A) : The secondary spread of the pathogen propagules that are identical in virulence is mostly responsible for epidemics.

Reason (R) : Secondary propagules are mostly asexually produced.

In light of the above statements, choose the correct answer from the options given below:

नीचे दो कथन दिए गए हैं, एक को अभिकथन (A) और दूसरे को कारण (R) के रूप में लेबल किया गया है:

अभिकथन (A) : रोगजनक प्रवर्ध्यों (propagules) का द्वितीयक प्रसार, जो उग्रता (virulence) में समरूप होते हैं, मुख्य रूप से महामारी (epidemics) के लिए उत्तरदायी होता है।

कारण (R) : द्वितीयक प्रवर्ध्य (secondary propagules) अधिकांशतः अलैंगिक रूप से उत्पन्न होते हैं।

उपरोक्त कथनों के आलोक में, नीचे दिए गए विकल्पों में से सही उत्तर चुनिए:

Both (A) and (R) are true and (R) is the correct explanation of (A) (A) और (R) दोनों सत्य हैं और (R), (A) की सही व्याख्या है Both (A) and (R) are true but (R) is NOT the correct explanation of (A) (A) और (R) दोनों सत्य हैं लेकिन (R), (A) की सही व्याख्या नहीं है (A) is true but (R) is false (A) सत्य है लेकिन (R) असत्य है (A) is false but (R) is true (A) असत्य है लेकिन (R) सत्य है

Epidemiology of Polycyclic Plant Diseases:

Assertion (A) is TRUE: In polycyclic plant diseases (e.g., late blight of potato, powdery mildews, rusts), explosive compound-interest epidemics are driven by multiple repeated cycles of secondary infection occurring within a single growing season.
Reason (R) is TRUE and correctly explains (A): Secondary propagules (e.g., conidia, sporangia, urediniospores) are produced asexually through mitosis. Because they are clonal products, they are genetically identical in virulence to the parent strain, allowing millions of equally virulent spores to rapidly colonize neighboring plants without meiotic gene segregation or loss of fitness.

Therefore, both (A) and (R) are true and (R) is the correct explanation of (A). Correct Answer: Option 1.

विस्तृत व्याख्या:

Epidemiology of Polycyclic Plant Diseases (पादप महामारी विज्ञान एवं द्वितीयक प्रसार):

Assertion (A) is TRUE: In polycyclic plant diseases (e.g., late blight of potato, powdery mildews, rusts), explosive compound-interest epidemics are driven by multiple repeated cycles of secondary infection occurring within a single growing season.
Reason (R) is TRUE and correctly explains (A): Secondary propagules (e.g., conidia, sporangia, urediniospores) are produced asexually through mitosis. Because they are clonal products, they are genetically identical in virulence to the parent strain, allowing millions of equally virulent spores to rapidly colonize neighboring plants without meiotic gene segregation or loss of fitness.

Therefore, both (A) and (R) are true and (R) is the correct explanation of (A). Correct Answer: Option 1.

Explanation not matching this question? क्या व्याख्या इस प्रश्न से मेल नहीं खा रही? Report

Q.2

ICAR AIEEA PG Plant Sciences 09 July 2023 (Shift 1) Paper (Q.75)

MCQ (Single Correct) +4 −1

Which of the following associations is favorable for Phosphorus (P) nutrition in higher plants?

उच्च पादपों में फॉस्फोरस (P) पोषण के लिए

निम्नलिखित में से कौन सा सहजीवी संबंध अनुकूल है?

Rhizobium-Legume symbiosis राइजोबियम-दलहन सहजीविता Azolla-Anabaena symbiosis एजोला-एनाबीना सहजीविता Actinorrhizal symbiosis एक्टिनोराइजल सहजीविता Mycorrhizal association माइकोराइजा संबंध

Mycorrhizal fungi (particularly Vesicular-Arbuscular Mycorrhizae / AM fungi of Glomeromycota) produce extensive extra-radical hyphal networks that traverse beyond the root phosphorus depletion zone. They solubilize fixed soil phosphates by exuding organic acids and phosphatase enzymes and absorb immobile orthophosphate ions ($H_2PO_4^-$), dramatically enhancing plant phosphorus nutrition.
Options 1, 2, and 3 (Rhizobium, Azolla-Anabaena, and Frankia-actinorrhizal associations) are biological nitrogen-fixing symbioses, not phosphorus-mobilizing.

Hence, Mycorrhizal association is correct.

उच्च पौधों में फॉस्फोरस (P) के अवशोषण के लिए माइकोराइजा संबंध (Mycorrhizal association) सबसे महत्वपूर्ण है।
कवक का बाह्य जाल (Extra-radical hyphae) मृदा में जड़ की पहुँच से बहुत दूर तक फैलकर फॉस्फेटेज एंजाइम और कार्बनिक अम्लों द्वारा स्थिर फॉस्फोरस को घुलनशील बनाकर पौधों को उपलब्ध कराता है।
विकल्प 1 (राइजोबियम), 2 (एजोला-एनाबीना) और 3 (एक्टिनोराइजा - फ्रैंकिया) मुख्य रूप से वायुमंडलीय नाइट्रोजन स्थिरीकरण से संबंधित हैं।

अतः सही उत्तर माइकोराइजा संबंध है।

Explanation not matching this question? क्या व्याख्या इस प्रश्न से मेल नहीं खा रही? Report

Q.3

ICAR AIEEA PG Plant Science 14 July 2023 Shift-1 Paper (Q.75)

MCQ (Single Correct) +4 −1