The genome of TMV codes for coat protein subunits consisting of | Agrigyan

• Human Pathogenic and Opportunistic Fungi:
• Group A (Candida and Aspergillus): Cause serious opportunistic mycoses (e.g., candidiasis, invasive pulmonary aspergillosis) in immunocompromised individuals, including chemotherapy, organ transplant, and AIDS patients.
• Group B (Histoplasma and Coccidioides): Dimorphic fungal pathogens causing systemic endemic respiratory and deep-tissue infections (histoplasmosis and coccidioidomycosis) with high mortality in immunocompromised hosts.
• Group C (Puccinia and Erysiphe): Obligate biotrophic plant pathogens (rusts and powdery mildews) that infect strictly plant hosts and are entirely incapable of causing human disease.
• Conclusion: Fungi in groups A and B cause human diseases in immunocompromised patients (Option 3).

Correct option: (3) A&B

• Vectors of Curtoviruses (Family Geminiviridae): The genus Curtovirus encompasses circular single-stranded DNA plant viruses (e.g., Beet curly top virus, BCTV).
• Vector Specificity: Curtoviruses are transmitted in a persistent, non-propagative manner specifically by leafhoppers (family Cicadellidae), primarily the beet leafhopper Circulifer tenellus.
• Comparison with other Geminiviridae:
• Begomovirus: Transmitted by whiteflies (Bemisia tabaci).
• Mastrevirus: Transmitted by leafhoppers (Cicadulina spp.).
• Topocuvirus: Transmitted by treehoppers.
• Conclusion: Curtovirus is transmitted by leafhoppers (Option 4).

Correct option: (4) Leafhopper

• Buffers for Plant Virus Extraction and Maintenance:
• Role of Buffer: Plant sap is naturally acidic and rich in oxidizing polyphenols that rapidly precipitate or denature viral nucleocapsids during tissue disruption.
• Phosphate Buffer: A neutral phosphate buffer ($0.05-0.1\text{ M}$ potassium or sodium phosphate buffer, $pH\ 7.0-7.2$), often supplemented with reducing agents (ascorbic acid, sodium sulfite), provides superior buffering capacity at physiological $pH$, maintaining virion ionic stability, solubility, and high infectivity during mechanical isolation and transmission.
• Conclusion: Phosphate buffer is best suited (Option 2).

Correct option: (2) Phosphate buffer