1. Which of the following enzymes is responsible for the reduction of nitrate (NO₃⁻) to nitrite (NO₂⁻) in higher plants?

  • A. Nitrite reductase
  • B. Nitrate reductase
  • C. Nitrogenase
  • D. Glutamine synthetase

Answer: B. Nitrate reductase

Explanation: Nitrate reductase catalyzes the cytosolic reduction of nitrate to nitrite using NADH or NADPH as the electron donor.

2. Which clay mineral has the highest potassium-fixing capacity?

  • A. Kaolinite
  • B. Illite
  • C. Vermiculite
  • D. Montmorillonite

Answer: C. Vermiculite

Explanation: Vermiculite possesses wedge-shaped interlayer sites that strongly fix potassium ions, making them temporarily unavailable to plants.

3. Which mating design is specifically used to estimate additive, dominance, and epistatic genetic variances in segregating populations?

  • A. Diallel analysis
  • B. Triple Test Cross (TTC)
  • C. Line × Tester analysis
  • D. Topcross analysis

Answer: B. Triple Test Cross (TTC)

Explanation: Triple Test Cross, proposed by Kearsey and Jinks, is an effective method for detecting epistasis and partitioning genetic variance.

4. Which pathogen is responsible for Karnal bunt of wheat?

  • A. Tilletia indica
  • B. Ustilago tritici
  • C. Puccinia graminis f. sp. tritici
  • D. Bipolaris sorokiniana

Answer: A. Tilletia indica

Explanation: Karnal bunt is caused by Tilletia indica, a quarantine-significant fungal pathogen affecting wheat grains.

5. Which multivariate statistical technique groups observations into homogeneous clusters based on similarity?

  • A. Factor analysis
  • B. Cluster analysis
  • C. Path analysis
  • D. Canonical correlation

Answer: B. Cluster analysis

Explanation: Cluster analysis classifies observations into groups so that members within a cluster are more similar to each other than to those in other clusters.

6. Which pigment functions as the primary photoreceptor for blue light-mediated responses such as phototropism?

  • A. Phytochrome
  • B. Cryptochrome
  • C. Phototropin
  • D. Protochlorophyllide

Answer: C. Phototropin

Explanation: Phototropins are flavoprotein blue-light receptors that regulate phototropism, chloroplast movement, and stomatal opening.

7. Which insect growth regulator inhibits chitin synthesis during insect molting?

  • A. Imidacloprid
  • B. Diflubenzuron
  • C. Chlorpyrifos
  • D. Malathion

Answer: B. Diflubenzuron

Explanation: Diflubenzuron belongs to the benzoylurea group and prevents chitin formation, disrupting molting in immature insects.

8. Which enzyme of glycolysis catalyzes the irreversible conversion of phosphoenolpyruvate (PEP) to pyruvate?

  • A. Enolase
  • B. Pyruvate kinase
  • C. Hexokinase
  • D. Phosphoglycerate mutase

Answer: B. Pyruvate kinase

Explanation: Pyruvate kinase catalyzes the final irreversible step of glycolysis, producing pyruvate and ATP.

9. Which crop growth analysis parameter is defined as the increase in plant dry weight per unit leaf area per unit time?

  • A. Crop Growth Rate (CGR)
  • B. Relative Growth Rate (RGR)
  • C. Net Assimilation Rate (NAR)
  • D. Leaf Area Index (LAI)

Answer: C. Net Assimilation Rate (NAR)

Explanation: NAR measures the photosynthetic efficiency of leaves and is expressed as dry matter produced per unit leaf area per unit time.

10. Which theorem states that allele and genotype frequencies remain constant from generation to generation in an infinitely large randomly mating population, in the absence of evolutionary forces?

  • A. Haldane Principle
  • B. Wright's Law
  • C. Hardy–Weinberg Principle
  • D. Fisher's Fundamental Theorem

Answer: C. Hardy–Weinberg Principle

Explanation: The Hardy–Weinberg Principle describes genetic equilibrium when no mutation, migration, selection, genetic drift, or non-random mating occurs.