• Pathogenesis by Sclerotium rolfsii:
• Statement (I) is true: Sclerotium rolfsii (teleomorph Athelia rolfsii) is a necrotrophic soil-borne pathogen causing collar rot and southern blight. During host tissue invasion, it secretes massive quantities of oxalic acid into the apoplast, which lowers ambient $pH$ ($\lt 3.5$) and chelates cell wall calcium ions.
• Statement (II) is false: Oxalic acid is a non-host-specific toxin (general phytotoxin) produced by many necrotrophic fungi (e.g., Sclerotinia sclerotiorum); it causes non-selective tissue maceration and necrosis across hundreds of unrelated plant species.
• Conclusion: Statement (I) is true but Statement (II) is false (Option 3).

Correct option: (3) Statement (I) is true but Statement (II) is false.

• Citrus Diseases and Integrated Disease Management:
• Pair-by-Pair Matching:
• Dry root rot of citrus (Macrophomina phaseolina/Fusarium solani) $\rightarrow$ (IV) Nursery management: Prevented by raising seedlings in sterile media, avoiding taproot damage, and strict nursery sanitation.
• Citrus canker (Xanthomonas citri subsp. citri) $\rightarrow$ (II) Pruning and burning of affected parts: Pruning cankered twigs before the monsoon and spraying copper bactericides reduces bacterial inoculum.
• Citrus tristeza virus (CTV) $\rightarrow$ (I) Use of tolerant rootstock: Managed by budding commercial scions onto CTV-tolerant rootstocks such as Rangpur lime, Rough lemon, or Trifoliate orange, avoiding susceptible sour orange.
• Citrus gummosis (Phytophthora spp.) $\rightarrow$ (III) Scrapping-off of diseased bark: Infected bark lesions are carefully scraped off using a sharp knife and painted with Bordeaux paste.
• Correct Choice: Option 1 matches (A)-(IV), (B)-(II), (C)-(I), (D)-(III).

Correct option: (1) (A) - (IV), (B)- I, (C)- 0), (B) - (I)

• Biology of Potato Virus Y (PVY):
• Statement (I) is true: Potato Virus Y (the type member of the genus Potyvirus) is transmitted naturally by over 50 aphid species (predominantly the green peach aphid, Myzus persicae) in a classic non-persistent, stylet-borne manner, where aphids acquire virions within seconds of probe feeding.
• Statement (II) is false: PVY virions are flexuous, filamentous particles ($730-740\text{ nm} \times 11\text{ nm}$) containing a positive-sense single-stranded RNA (+ssRNA) genome ($\sim 9.7\text{ kb}$), NOT double-stranded RNA (dsRNA).
• Conclusion: Statement (I) is true but Statement (II) is false (Option 3).

Correct option: (3) Statement (I) is true but Statement (II) is false.