Given below are two statements Statement (I): Mg? ion is... | Agrigyan

• 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)

• Biology of Clavibacter xyli subsp. xyli (Leifsonia xyli subsp. xyli):
• is true: It is the causal agent of Ratoon Stunting Disease (RSD) of sugarcane, causing severe vascular clogging, red-orange fibrovascular discoloration in nodal regions, and progressive yield decline.
• is false: It is a Gram-positive, high-G+C coryneform actinobacterium, not Gram-negative.
• is true: It appears morphologically as small, slender, pleomorphic coryneform rods (often with clubbed or branched ends).
• is false: The cells are strictly non-motile and lack flagella.
• Conclusion: Features (A) and (C) only are true (Option 3).

Correct option: (3) (A) and (C) only.

• Infection Process of Foliar Fungal Pathogens:

• Germ tube (C): Conidium germinates on the host leaf cuticle in the presence of free water to produce a vegetative germ tube.
• Appressorium (D): The germ tube tip swells and forms a melanized, dome-shaped infection structure called an appressorium, generating extreme turgor pressure.
• Penetration peg (A): A slender penetration hypha emerges from the appressorium base, piercing the host cuticle and epidermal cell wall via mechanical force and cell-wall degrading enzymes (cutinases, cellulases).
• Haustorium (B): Within the host mesophyll cell, the invading hypha invaginates the plant plasma membrane to differentiate a specialized nutrient-absorbing haustorium.
  • Sequential Order: (C) $\rightarrow$ (D) $\rightarrow$ (A) $\rightarrow$ (B) (Option 2).