Agronomy Plant Genetics and Breeding 2 — Questions and Answers
Question 1: What is the primary goal of marker-assisted selection (MAS) in plant breeding?
- To eliminate the need for field trials
- To use DNA markers linked to traits for faster, more accurate selection (Correct answer)
- To identify phenotypically superior plants by eye
- To cross distantly related species
Correct answer: To use DNA markers linked to traits for faster, more accurate selection
MAS uses molecular markers associated with desired traits to select superior plants without waiting for phenotypic expression, speeding up breeding cycles.
Question 2: Polyploidy in plants refers to what condition?
- Having only one set of chromosomes
- Having more than two complete sets of chromosomes (Correct answer)
- Having chromosomes of unequal size
- Lacking a nucleus in mature cells
Correct answer: Having more than two complete sets of chromosomes
Polyploidy is the condition of having three or more complete sets of chromosomes; it is common in many important crop plants like wheat and cotton.
Question 3: Which trait in Bt corn was introduced through genetic engineering?
- Drought tolerance
- Herbicide resistance to glyphosate
- Insect resistance via Bacillus thuringiensis toxin (Correct answer)
- Nitrogen fixation
Correct answer: Insect resistance via Bacillus thuringiensis toxin
Bt corn contains a gene from the soil bacterium Bacillus thuringiensis that produces proteins toxic to specific insect pests like European corn borer.
Question 4: What does heritability (h²) measure in a plant breeding context?
- The probability a trait is inherited by all offspring
- The proportion of total phenotypic variation due to genetic variation (Correct answer)
- The number of genes controlling a trait
- The dominance relationship between alleles
Correct answer: The proportion of total phenotypic variation due to genetic variation
Heritability estimates the fraction of observed variation in a trait that is attributable to genetic differences rather than environmental factors.
Question 5: What is the purpose of a testcross in plant breeding evaluation?
- To confirm a plant is diploid
- To evaluate the general combining ability of inbred lines using a common tester (Correct answer)
- To detect chromosome abnormalities
- To measure germination rate under stress
Correct answer: To evaluate the general combining ability of inbred lines using a common tester
Testcrossing inbred lines to a common tester allows breeders to assess their combining ability and predict hybrid performance.
Question 6: Open-pollinated varieties differ from hybrid varieties primarily because they do what?
- Produce sterile seeds
- Breed true from saved seed and maintain genetic consistency (Correct answer)
- Always outyield commercial hybrids
- Require cross-pollination each season
Correct answer: Breed true from saved seed and maintain genetic consistency
Open-pollinated varieties are genetically stable populations that breed true when seed is saved and replanted, unlike hybrids which segregate in F2.
Agronomy Plant Genetics and Breeding 2
What is the primary goal of marker-assisted selection (MAS) in plant breeding?