1. Which of the following experimental designs is commonly used in plant breeding to test the effect of different varieties or treatments?
a) Factorial design
b) Randomized Complete Block Design (RCBD)
c) Split-plot design
d) Latin square design
Answer: b) Randomized Complete Block Design (RCBD)
Explanation: The Randomized Complete Block Design (RCBD) is widely used in plant breeding experiments because it accounts for variability in the experimental field, ensuring that treatment comparisons are not influenced by environmental factors.
2. In plant breeding, what is the purpose of conducting a diallel cross experiment?
a) To test the genetic purity of the plant varieties
b) To assess the heterosis or hybrid vigor in a set of crosses
c) To determine the best breeding method for a crop species
d) To evaluate the environmental interaction of different plant varieties
Answer: b) To assess the heterosis or hybrid vigor in a set of crosses
Explanation: A diallel cross experiment involves crossing a set of parent lines with each other, allowing plant breeders to assess the heterosis (hybrid vigor) and identify superior hybrids for further breeding.
3. What is the key advantage of using a genetic variance analysis in plant breeding experiments?
a) It helps in determining the ideal planting density for crop varieties
b) It quantifies the contribution of different genetic components to the phenotype
c) It measures the yield potential of different varieties in a given environment
d) It identifies the disease resistance of different plant varieties
Answer: b) It quantifies the contribution of different genetic components to the phenotype
Explanation: Genetic variance analysis in plant breeding helps determine the contribution of various genetic factors (additive, dominance, and epistasis) to the observed phenotypic variation, which is essential for designing effective breeding programs.
4. In a plant breeding experiment, the term “broad-sense heritability” (H²) refers to:
a) The proportion of phenotypic variance attributable to additive genetic variance
b) The proportion of phenotypic variance attributable to both additive and non-additive genetic variance
c) The proportion of phenotypic variance attributable to environmental factors
d) The genetic relationship between the parent and the progeny
Answer: b) The proportion of phenotypic variance attributable to both additive and non-additive genetic variance
Explanation: Broad-sense heritability (H²) refers to the proportion of total phenotypic variance that is explained by genetic variance, which includes both additive genetic variance and non-additive genetic variance (dominance and epistasis).
5. What is the primary purpose of conducting a backcross in plant breeding?
a) To test the genetic purity of a variety
b) To introduce new traits from a donor parent into an elite variety
c) To identify the best combination of genetic traits in a population
d) To select superior inbred lines from a population
Answer: b) To introduce new traits from a donor parent into an elite variety
Explanation: A backcross is used in plant breeding to introduce specific traits (such as disease resistance) from a donor parent into an elite variety. It involves crossing the hybrid offspring back with one of the parental lines to maintain desirable characteristics.
6. In a plant breeding experiment, if two parents exhibit high general combining ability (GCA), what does this imply?
a) The parents produce low-quality hybrids
b) The parents are likely to have high heterosis when crossed
c) The parents can be used in crosses to produce high-yielding progeny
d) The parents have low genetic diversity
Answer: c) The parents can be used in crosses to produce high-yielding progeny
Explanation: High general combining ability (GCA) indicates that the parents are good contributors to the genetic potential of the progeny. When crossed, they are likely to produce high-yielding and desirable offspring.
7. What does reciprocal cross experimentation help determine in plant breeding?
a) The environmental impact on genetic inheritance
b) The impact of cytoplasmic inheritance on trait expression
c) The genetic purity of the seed stock
d) The influence of mating systems on the offspring
Answer: b) The impact of cytoplasmic inheritance on trait expression
Explanation: Reciprocal cross experiments help determine the role of the cytoplasm (inherited maternally) in the expression of specific traits. Differences in the offspring resulting from reciprocal crosses indicate cytoplasmic inheritance.
8. In plant breeding, what is the purpose of mass selection?
a) To select a few elite individuals from a population based on specific traits
b) To select plants with the highest genetic diversity
c) To choose the highest yielding variety for seed production
d) To select plants based on their visual characteristics only
Answer: a) To select a few elite individuals from a population based on specific traits
Explanation: Mass selection is a method in which breeders select individual plants exhibiting desirable traits from a population and use them to form the next generation. It is effective for improving traits that are controlled by a large number of genes.
9. Which type of mutation is intentionally induced in plants during mutagenesis experiments in plant breeding?
a) Silent mutations
b) Lethal mutations
c) Beneficial mutations for trait improvement
d) Random mutations for genetic diversity
Answer: c) Beneficial mutations for trait improvement
Explanation: In mutagenesis experiments, breeders use physical or chemical agents to induce mutations in plants to create beneficial traits, such as increased resistance to diseases or improved yield.
10. Which of the following is the most appropriate breeding method for improving traits that are controlled by polygenic inheritance?
a) Inbreeding
b) Mass selection
c) Hybridization
d) Mutation breeding
Answer: b) Mass selection
Explanation: Polygenic traits, controlled by many genes, are best improved through methods like mass selection, where individuals with the desired traits are selected from the population and propagated over several generations.
11. Which of the following breeding methods would be most appropriate for developing a variety of maize with improved drought tolerance and high yield potential?
a) Mutation breeding
b) Marker-assisted selection (MAS)
c) Reciprocal crossing
d) Inbreeding
Answer: b) Marker-assisted selection (MAS)
Explanation: Marker-assisted selection (MAS) allows breeders to select for drought tolerance and high yield potential based on genetic markers linked to these traits, making the breeding process more efficient and precise.
12. In testcross experiments, what is the main objective?
a) To determine the genotype of an individual with an unknown genetic composition
b) To assess the quality of seed production in hybrid varieties
c) To evaluate the genetic diversity of a population
d) To improve the visual characteristics of a plant
Answer: a) To determine the genotype of an individual with an unknown genetic composition
Explanation: A testcross involves crossing an individual with a known genotype (usually recessive) to determine the genotype of the other individual. It is used to test whether an individual is homozygous or heterozygous for a particular trait.
13. In plant breeding, what does the term “heterosis” (hybrid vigor) refer to?
a) The improved performance of a hybrid compared to its parents
b) The genetic uniformity within a hybrid population
c) The increase in mutation rate during hybridization
d) The reduction of traits from the parental lines
Answer: a) The improved performance of a hybrid compared to its parents
Explanation: Heterosis, or hybrid vigor, refers to the phenomenon where hybrid offspring exhibit superior traits, such as increased yield, disease resistance, or growth rate, compared to their parent plants.
14. In conventional breeding, the method used for transferring specific traits from one plant to another is called:
a) Genetic engineering
b) Hybridization
c) Polyploidy
d) Biolistics
Answer: b) Hybridization
Explanation: Hybridization in conventional breeding involves crossing two genetically different plants to transfer desirable traits from one parent to the other, usually with the goal of improving yield, disease resistance, or other characteristics.
15. Which of the following statistical tools is most commonly used to analyze the genetic improvement of quantitative traits in plant breeding?
a) Correlation analysis
b) Analysis of variance (ANOVA)
c) Cluster analysis
d) Path coefficient analysis
Answer: b) Analysis of variance (ANOVA)
Explanation: Analysis of variance (ANOVA) is commonly used in plant breeding to analyze the effects of different breeding treatments on quantitative traits, helping to determine if the observed differences are statistically significant.