अपनी अत्यधिक संवेदनशीलता के कारण केले की किस्म "ग्रोस मिशेल"...

सभी विषय सामान्य कृषि, फसल उत्पादन एवं मृदा विज्ञान कोशिका विज्ञान, आनुवंशिकी, कार्यिकी, जैव रसायन एवं पादप सुरक्षा आनुवंशिकी, पादप रोग विज्ञान, बीज विज्ञान एवं कृषि सूक्ष्मजीव विज्ञान खाद्य व औद्योगिक सूक्ष्मजीव विज्ञान, ग्रामीण विकास एवं कृषि अनुसंधान संरचना

Q.41

ICAR AIEEA PG 2024 - Plant Sciences

Assertion & Reason +4 −1

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

Assertion (A) : In a breeding program, it is relatively easy to handle the 'major genes' for resistance, but it leads to the boom and bust cycle due to the quick breakdown of resistance in the varieties.

Reason (R) : Polygenic or partial resistance is durable but breeding for this type of resistance is problematic.

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) : एक प्रजनन कार्यक्रम में, प्रतिरोध के 'प्रमुख जीनों' (major genes / vertical resistance) को संभालना अपेक्षाकृत आसान होता है, लेकिन यह किस्मों में प्रतिरोध के तेजी से टूटने के कारण 'बूम और बस्ट चक्र' (boom and bust cycle) की ओर ले जाता है।

कारण (R) : बहुजीनी या आंशिक प्रतिरोध (polygenic or partial resistance / horizontal resistance) टिकाऊ होता है लेकिन इस प्रकार के प्रतिरोध के लिए प्रजनन करना समस्याग्रस्त/जटिल होता है।

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

Vertical vs. Horizontal Resistance in Plant Breeding:

Assertion (A) is TRUE: Major gene (vertical / race-specific) resistance is governed by one or few oligogenes following simple Mendelian inheritance, making it easy to select in early segregating generations. However, widespread cultivation of varieties carrying a single major gene exerts intense selection pressure on the pathogen population, leading to the emergence of virulent virulent pathogen races that rapidly overcome the resistance (the boom-and-bust cycle).
Reason (R) is TRUE: Horizontal (polygenic / partial / race-non-specific) resistance is controlled by multiple minor genes (QTLs) and is durable over long evolutionary periods because pathogens cannot overcome it through single mutations. However, breeding for partial resistance is laborious and difficult because each gene confers a small effect, is subject to environmental variation, and requires complex quantitative evaluation.
Both statements are scientifically accurate, but Reason (R) explains the nature of horizontal resistance, not why major genes cause the boom-and-bust cycle (which is caused by directional selection of virulent pathogen races).

Therefore, both (A) and (R) are true, but (R) is NOT the correct explanation of (A). Correct Answer: Option 2.

विस्तृत व्याख्या:

Vertical vs. Horizontal Resistance in Plant Breeding (पादप रोग प्रतिरोध प्रजनन - Van der Plank, 1963):

Assertion (A) is TRUE: Major gene (vertical / race-specific) resistance is governed by one or few oligogenes following simple Mendelian inheritance, making it easy to select in early segregating generations. However, widespread cultivation of varieties carrying a single major gene exerts intense selection pressure on the pathogen population, leading to the emergence of virulent virulent pathogen races that rapidly overcome the resistance (the boom-and-bust cycle).
Reason (R) is TRUE: Horizontal (polygenic / partial / race-non-specific) resistance is controlled by multiple minor genes (QTLs) and is durable over long evolutionary periods because pathogens cannot overcome it through single mutations. However, breeding for partial resistance is laborious and difficult because each gene confers a small effect, is subject to environmental variation, and requires complex quantitative evaluation.
Both statements are scientifically accurate, but Reason (R) explains the nature of horizontal resistance, not why major genes cause the boom-and-bust cycle (which is caused by directional selection of virulent pathogen races).

Therefore, both (A) and (R) are true, but (R) is NOT the correct explanation of (A). Correct Answer: Option 2.

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

Q.42

ICAR AIEEA PG 2024 - Plant Sciences

MCQ (Single Correct) +4 −1

Which of the following is NOT a feature of Oomycetes plant pathogens?

निम्नलिखित में से कौन सा ऊमाईसीट्स (Oomycetes) पादप रोगजनकों का लक्षण नहीं है?

Motile spores गतिशील बीजाणु Coloured spores रंगीन बीजाणु Hyaline mycelium कांचाभ कवकजाल Coenocytic mycelium संकोशिकी कवकजाल

Distinguishing Characteristics of Oomycetes:

Oomycetes (water molds, downy mildews, Phytophthora, Pythium) belong to the kingdom Stramenopila / Chromista, distinct from true fungi (Eumycota).
Key Features of Oomycetes:
Coenocytic mycelium: Aseptate, multinucleate hyphae (with cell walls composed predominantly of $\beta$-glucans and cellulose, lacking chitin).
Hyaline mycelium and sporangia: Colorless, transparent structures.
Motile zoospores: Characteristic biflagellate heterokont zoospores bearing one forward-directed tinsel flagellum and one backward-directed whiplash flagellum.
They do NOT produce pigmented or coloured spores (such as melanized or dark spores found in Ascomycota/Basidiomycota like Alternaria or Puccinia).

Therefore, 'Coloured spores' is NOT a feature of Oomycetes. Correct Answer: Option 2 (Coloured spores).

विस्तृत व्याख्या:

Distinguishing Characteristics of Oomycetes (ऊमाईसीट्स के प्रमुख लक्षण):

Oomycetes (water molds, downy mildews, Phytophthora, Pythium) belong to the kingdom Stramenopila / Chromista, distinct from true fungi (Eumycota).
Key Features of Oomycetes:
Coenocytic mycelium: Aseptate, multinucleate hyphae (with cell walls composed predominantly of $\beta$-glucans and cellulose, lacking chitin).
Hyaline mycelium and sporangia: Colorless, transparent structures.
Motile zoospores: Characteristic biflagellate heterokont zoospores bearing one forward-directed tinsel flagellum and one backward-directed whiplash flagellum.
They do NOT produce pigmented or coloured spores (such as melanized or dark spores found in Ascomycota/Basidiomycota like Alternaria or Puccinia).

Therefore, 'Coloured spores' is NOT a feature of Oomycetes. Correct Answer: Option 2 (Coloured spores).

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

Q.43

ICAR AIEEA PG 2024 - Plant Sciences

MCQ (Single Correct) +4 −1

Which of the following is known to cause abnormal and unlimited proliferation of plant cells?

निम्नलिखित में से कौन पादप कोशिकाओं के असामान्य और असीमित प्रवर्धन (proliferation / गिल्टी बनना) का कारण बनने के लिए जाना जाता है?

Agrobacterium एग्रोबैक्टीरियम (Agrobacterium) Rhizobium राइजोबियम (Rhizobium) Xanthomonas जैंथोमोनास (Xanthomonas) Erwinia इरविनिया (Erwinia)

Q.44

ICAR AIEEA PG 2024 - Plant Sciences

MCQ (Single Correct) +4 −1

Which of the following is one of the key adaptive features of fungal spores that aid them in long-distance transmission?

निम्नलिखित में से कौन सा कवक बीजाणुओं (fungal spores) का एक प्रमुख अनुकूलन लक्षण है जो उन्हें लंबी दूरी के संचरण (long-distance transmission) में सहायता करता है?

Long flagella like appendages लंबे कशाभिका जैसे उपांग Low melanin content कम मेलेनिन सामग्री High melanin contents उच्च मेलेनिन सामग्री Short flagella like appendages छोटे कशाभिका जैसे उपांग

Spore Adaptations for Aerobiological Dispersal:

Fungal spores carried through the upper atmosphere over hundreds of kilometers (e.g., urediniospores of Puccinia graminis, conidia of Alternaria and Cladosporium) are exposed to severe environmental hazards: intense solar ultraviolet (UV) radiation and severe desiccation.
Melanin deposited in the cell walls acts as a powerful photoprotective pigment and free-radical scavenger, absorbing lethal UV-B/UV-A radiation and conferring structural rigidity against desiccation.
Airborne spores rely entirely on passive wind currents (anemochory) and do not possess flagella (flagella are present only in aquatic motile zoospores, not aerial spores).

Therefore, high melanin content is the key adaptive feature ensuring spore survival during long-distance transmission. Correct Answer: Option 3 (High melanin contents).

विस्तृत व्याख्या:

Spore Adaptations for Aerobiological Dispersal (कवक बीजाणुओं के अनुकूलन):

Fungal spores carried through the upper atmosphere over hundreds of kilometers (e.g., urediniospores of Puccinia graminis, conidia of Alternaria and Cladosporium) are exposed to severe environmental hazards: intense solar ultraviolet (UV) radiation and severe desiccation.
Melanin deposited in the cell walls acts as a powerful photoprotective pigment and free-radical scavenger, absorbing lethal UV-B/UV-A radiation and conferring structural rigidity against desiccation.
Airborne spores rely entirely on passive wind currents (anemochory) and do not possess flagella (flagella are present only in aquatic motile zoospores, not aerial spores).

Therefore, high melanin content is the key adaptive feature ensuring spore survival during long-distance transmission. Correct Answer: Option 3 (High melanin contents).

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

Q.45

ICAR AIEEA PG 2024 - Plant Sciences

MCQ (Single Correct) +4 −1

Which of the following was responsible for the extinction of the Banana Variety "Gros Michel" from the market due to its high susceptibility?

अपनी अत्यधिक संवेदनशीलता के कारण केले की किस्म "ग्रोस मिशेल" (Gros Michel) के बाजार से विलुप्त/हटने के लिए

निम्नलिखित में से कौन सा रोगकारक उत्तरदायी था?

Fusarium oxysporum f. sp. cubense race 1 Fusarium oxysporum f. sp. cubense race 1 Fusarium oxysporum f. sp. cubense race 4 or tropical race 4 Fusarium oxysporum f. sp. cubense race 4 or tropical race 4 Ralstonia solanacearum race 2 Ralstonia solanacearum race 2 Ralstonia solanacearum race 4 Ralstonia solanacearum race 4

Panama Disease of Banana and Gros Michel Extinction:

During the first half of the 20th century, 'Gros Michel' was the dominant commercial export banana cultivar worldwide.
In the 1950s, an epidemic of Panama wilt caused by Fusarium oxysporum f. sp. cubense race 1 (Foc race 1) wiped out commercial plantations of 'Gros Michel' across Central America and the Caribbean.
This forced the global banana industry to completely abandon 'Gros Michel' and switch to resistant cultivars belonging to the Cavendish subgroup (which are resistant to race 1, though now threatened by Tropical Race 4 / TR4).
Bacterial wilt / Moko disease is caused by Ralstonia solanacearum race 2, but the historical cultivar extinction was caused by Foc race 1.

Correct Answer: Option 1 (Fusarium oxysporum f. sp. cubense race 1).

विस्तृत व्याख्या:

Panama Disease of Banana and Gros Michel Extinction (पनामा विल्ट - ग्रोस मिशेल का संकट):

During the first half of the 20th century, 'Gros Michel' was the dominant commercial export banana cultivar worldwide.
In the 1950s, an epidemic of Panama wilt caused by Fusarium oxysporum f. sp. cubense race 1 (Foc race 1) wiped out commercial plantations of 'Gros Michel' across Central America and the Caribbean.
This forced the global banana industry to completely abandon 'Gros Michel' and switch to resistant cultivars belonging to the Cavendish subgroup (which are resistant to race 1, though now threatened by Tropical Race 4 / TR4).
Bacterial wilt / Moko disease is caused by Ralstonia solanacearum race 2, but the historical cultivar extinction was caused by Foc race 1.

Correct Answer: Option 1 (Fusarium oxysporum f. sp. cubense race 1).

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