1. Which enzyme catalyzes the first committed step of the shikimate pathway leading to the biosynthesis of aromatic amino acids in plants?

  • A. Chorismate mutase
  • B. 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase
  • C. EPSP synthase
  • D. Phenylalanine ammonia-lyase

Answer: B. 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase

Explanation: DAHP synthase catalyzes the condensation of phosphoenolpyruvate and erythrose-4-phosphate, the first committed reaction of the shikimate pathway.

2. The Gapon exchange coefficient is primarily associated with the study of:

  • A. Soil phosphorus fixation
  • B. Cation exchange equilibrium between Na⁺ and Ca²⁺
  • C. Soil organic carbon decomposition
  • D. Nitrogen mineralization

Answer: B. Cation exchange equilibrium between Na⁺ and Ca²⁺

Explanation: The Gapon equation describes the equilibrium exchange between sodium and calcium ions on soil exchange sites and is important in sodic soil studies.

3. In plant breeding, the Line × Tester analysis proposed by Kempthorne is primarily used to estimate:

  • A. Mutation frequency
  • B. General and specific combining ability
  • C. Linkage distance
  • D. Heritability only

Answer: B. General and specific combining ability

Explanation: Line × Tester analysis partitions genetic variance into general combining ability (GCA) and specific combining ability (SCA).

4. The avirulence (Avr) gene-for-gene hypothesis explaining host-pathogen interactions was proposed by:

  • A. H.H. Flor
  • B. Robert Koch
  • C. Louis Pasteur
  • D. E.C. Stakman

Answer: A. H.H. Flor

Explanation: H.H. Flor proposed the gene-for-gene hypothesis while studying flax and flax rust interactions.

5. Which statistical method is most appropriate for estimating the relationship between one dependent variable and several independent variables?

  • A. Paired t-test
  • B. Multiple linear regression
  • C. Chi-square test
  • D. Sign test

Answer: B. Multiple linear regression

Explanation: Multiple linear regression models the relationship between one response variable and two or more predictor variables.

6. Which phytochrome form is biologically active and promotes photomorphogenic responses in plants?

  • A. Pr
  • B. Pfr
  • C. Protochlorophyllide
  • D. Chlorophyll a

Answer: B. Pfr

Explanation: The Pfr form of phytochrome is the physiologically active form that regulates seed germination, flowering, and shade avoidance.

7. Which parasitoid is extensively used in biological control programs against lepidopteran egg pests?

  • A. Chrysoperla zastrowi sillemi
  • B. Trichogramma chilonis
  • C. Cryptolaemus montrouzieri
  • D. Coccinella septempunctata

Answer: B. Trichogramma chilonis

Explanation: Trichogramma chilonis is an egg parasitoid widely released for the biological control of lepidopteran pests in field crops.

8. Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA before entry into the tricarboxylic acid cycle?

  • A. Pyruvate carboxylase
  • B. Pyruvate dehydrogenase complex
  • C. Alcohol dehydrogenase
  • D. Lactate dehydrogenase

Answer: B. Pyruvate dehydrogenase complex

Explanation: The pyruvate dehydrogenase complex catalyzes oxidative decarboxylation of pyruvate to acetyl-CoA, producing NADH.

9. The crop growth rate (CGR) is expressed as:

  • A. Increase in plant height per unit time
  • B. Increase in dry matter per unit land area per unit time
  • C. Leaf area per plant
  • D. Grain yield per plant

Answer: B. Increase in dry matter per unit land area per unit time

Explanation: CGR measures the rate of biomass accumulation over a unit ground area and time, usually expressed as g m⁻² day⁻¹.

10. Which population is expected to have the highest level of heterozygosity under Hardy–Weinberg equilibrium?

  • A. p = 0.1, q = 0.9
  • B. p = 0.2, q = 0.8
  • C. p = 0.5, q = 0.5
  • D. p = 0.9, q = 0.1

Answer: C. p = 0.5, q = 0.5

Explanation: Expected heterozygosity (2pq) reaches its maximum value (0.5) when allele frequencies are equal (p = q = 0.5).