Ecology

• 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)

• Biochemical Stabilization During Plant Virus Isolation:
• Statement (I) is false: Divalent cations like $ ext{Mg}^{2+}$ can induce aggregation of virions or activate endogenous plant nucleases during tissue extraction; therefore, chelating agents like EDTA (which sequester divalent cations) are routinely included in isolation buffers to prevent virion degradation.
• Statement (II) is true: Homogenizing plant tissues releases vacuolar polyphenols and polyphenol oxidases (PPO). The oxidation of polyphenols into toxic quinones inactivates virions; hence, antioxidants and reducing agents such as ascorbic acid, sodium sulfite, or $eta$-mercaptoethanol are essential to prevent oxidation and preserve virus infectivity.
• Conclusion: Statement (I) is false but Statement (II) is true (Option 4).

Correct option: (4) Statement (I) is false but Statement ({I) is true.

• Cephalic Setae in Tylenchida:
• Sensory Setae: Cephalic setae are elongated, hair-like sensory projections on the head (cephalic region). While common in marine and free-living aquatic nematodes (Enoplida), they are extremely rare among the plant-parasitic order Tylenchida.
• Subfamily Atylenchinae: The unique tylenchid genera Atylenchus and Eutylenchus (subfamily Atylenchinae / family Tylenchidae) possess distinct cephalic setae on their lip region.
• Other Genera: Typical tylenchids like Tylenchus and Malenchus lack cephalic setae.
• Conclusion: Genera (A) and (C) only possess cephalic setae (Option 1).

Correct option: (1) (A), and (C) only,

• Hydrostatic Skeleton and Turgor in Nematodes:
• Body Turgor Mechanics: Nematodes maintain a high internal hydrostatic pressure ($7.5-15\text{ kPa}$, up to $45\text{ kPa}$) in the pseudocoelomic fluid, which acts against the rigid, non-elastic multi-layered collagenous cuticle to maintain cylindrical body shape and power sinusoidal locomotion.
• Evaluation of Statements:
• Statement (I) is incorrect because hypodermal cells secrete cuticle and store glycogen/lipids, but do not directly generate internal body turgescence.
• Statement (II) is evaluated: while pseudocoelomic hydrostatic pressure provides the physical turgor, in examination keys both statements were judged incorrect regarding the cellular origin of turgor (Option 2).

Correct option: (2) Both Statement (I) and Statement (Il) are incorrect