Mycology

• Insect Vectors and Plant Virus Transmission:
• Pair-by-Pair Matching:
• Aphids $\rightarrow$ (III) Potyvirus: Aphids (e.g., Myzus persicae, Aphis gossypii) are the primary non-persistent stylet-borne vectors of the vast Potyviridae family (e.g., Potato virus Y, Papaya ringspot virus).
• Thrips $\rightarrow$ (I) Tospovirus: Thrips (e.g., Frankliniella occidentalis, Thrips palmi) transmit tospoviruses (e.g., Tomato spotted wilt virus, Groundnut bud necrosis virus) in a circulative propagative manner.
• Mealybugs $\rightarrow$ (IV) Badnavirus: Mealybugs (Pseudococcidae) transmit badnaviruses such as Sugarcane bacilliform virus and Cacao swollen shoot virus in a semi-persistent manner.
• Whiteflies $\rightarrow$ (II) Begomovirus: Whitefly (Bemisia tabaci) is the obligate circulative-persistent vector of geminiviruses (genus Begomovirus, e.g., Tomato leaf curl virus, Cotton leaf curl virus).
• Correct Choice: Option 2 represents (A)-(III), (B)-(I), (C)-(IV), (D)-(II).

Correct option: (2) (A)- (IID, (B) - (0), (C) - (IV), (B) - (I)

• 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

• Discovery of Viroids: In 1971, the Swiss-American plant pathologist Theodor O. Diener (T. O. Diener) discovered that the causal agent of Potato Spindle Tuber Disease (PSTD) was not a virus, but a novel subviral infectious entity.
• Nature of Viroids: Diener proved that the agent consisted exclusively of a tiny, circular, single-stranded non-protein-coding RNA molecule ($246-467\text{ nt}$) devoid of any protective protein coat, for which he coined the term 'viroid'.
• Other Scientists Listed:
• W. M. Stanley (1935): Crystallized Tobacco Mosaic Virus (TMV).
• F. C. Bawden & N. W. Pirie (1937): Demonstrated that TMV virions contain both protein and RNA.
• Conclusion: T. O. Diener reported that potato spindle tuber disease is caused by viroids (Option 4).

Correct option: (4) T.0. Diener