Agronomy Plant Genetics and Breeding 1 — Questions and Answers
Question 1: What is a hybrid variety in crop production?
- A variety developed through genetic mutation
- The F1 offspring of two inbred parent lines (Correct answer)
- A variety adapted to tropical climates
- An open-pollinated landrace variety
Correct answer: The F1 offspring of two inbred parent lines
A hybrid variety is the first-generation (F1) offspring produced by crossing two genetically distinct inbred parent lines, exhibiting hybrid vigor.
Question 2: What is 'heterosis' (hybrid vigor) in plant breeding?
- Reduced yield in hybrid offspring
- Superior performance of F1 hybrids over parental averages (Correct answer)
- Genetic uniformity in a population
- Resistance to cross-pollination
Correct answer: Superior performance of F1 hybrids over parental averages
Heterosis refers to the superior performance of F1 hybrid offspring compared to the average of their parent inbred lines.
Question 3: Which breeding method is most commonly used to develop new inbred lines for hybrid corn production?
- Mass selection
- Selfing (self-pollination) for multiple generations (Correct answer)
- Backcrossing
- Mutation breeding
Correct answer: Selfing (self-pollination) for multiple generations
Repeated self-pollination over 6–8 generations produces highly homozygous inbred lines used as parents in hybrid seed production.
Question 4: What does the term 'quantitative trait' mean in plant genetics?
- A trait controlled by a single dominant gene
- A trait controlled by many genes showing continuous variation (Correct answer)
- A trait visible only in recessive plants
- A trait unaffected by the environment
Correct answer: A trait controlled by many genes showing continuous variation
Quantitative traits like yield and plant height are controlled by many genes with small individual effects and show continuous variation in populations.
Question 5: Backcrossing in plant breeding is primarily used to do what?
- Increase genetic diversity
- Transfer a single trait into an elite variety while preserving its background (Correct answer)
- Create new inbred lines
- Induce polyploidy
Correct answer: Transfer a single trait into an elite variety while preserving its background
Backcrossing involves repeated crosses to the recurrent (elite) parent to recover its genome while retaining a desired trait from the donor parent.
Question 6: GMO crops produced using Agrobacterium-mediated transformation are transformed how?
- By exposing seeds to radiation
- By inserting foreign DNA via the Ti plasmid into plant cells (Correct answer)
- By chemical mutagenesis of pollen
- By grafting onto transgenic rootstocks
Correct answer: By inserting foreign DNA via the Ti plasmid into plant cells
Agrobacterium tumefaciens naturally transfers its Ti plasmid DNA into plant cells; scientists exploit this to insert desired genes.
Agronomy Plant Genetics and Breeding 1
What is a hybrid variety in crop production?