Scientific Officer-Plant Breeding-Practice-4

Practice questions

1. What is the main feature of the pedigree method of selection?
   • Recording the ancestry of selected plants across generations
   • Mixing seeds from all plants without recording parentage
   • Selecting plants only through molecular markers
   • Producing hybrids without evaluating their parents
2. In the bulk method of breeding, what generally happens during the early generations?
   • Seeds from selected populations are harvested and bulked together
   • Every plant is maintained as a separate pure line
   • All plants are crossed with a single tester
   • Only vegetatively propagated plants are retained
3. What is the main principle of the single-seed descent method?
   • Advancing generations by retaining one seed from each plant
   • Selecting only the tallest plant in every generation
   • Crossing every plant with a different species
   • Mixing seed from unrelated commercial varieties
4. What is inbreeding depression in crop plants?
   • Reduced vigour or performance resulting from inbreeding
   • Increased hybrid vigour after crossing unrelated parents
   • Increased genetic variation through mutation
   • Improved performance caused by environmental uniformity
5. In plant breeding, what does selection differential represent?
   • The difference between the mean of selected parents and the original population mean
   • The difference between seed moisture and seed purity
   • The difference between two chromosome numbers
   • The difference between germination and seed dormancy
6. Which factor generally increases the expected response to selection for a quantitative trait?
   • Higher narrow-sense heritability, with other factors unchanged
   • Lower selection intensity, with other factors unchanged
   • Greater environmental variation, with other factors unchanged
   • Lower additive genetic variation, with other factors unchanged
7. What is a characteristic feature of vertical disease resistance in plants?
   • It is often race-specific resistance against particular pathogen races
   • It always provides equal protection against every pathogen race
   • It is caused only by improved soil fertility
   • It prevents all forms of insect damage
8. Which description best fits horizontal disease resistance?
   • Quantitative resistance that is often effective against several pathogen races
   • Resistance that always depends on one major gene
   • Resistance that occurs only during seed storage
   • Resistance that prevents all environmental stress
9. What does the gene-for-gene hypothesis describe?
   • A relationship between plant resistance genes and corresponding pathogen avirulence genes
   • The inheritance of seed colour through environmental effects only
   • The relationship between fertilizer dose and plant height
   • The development of hybrids through chromosome doubling
10. What is disease escape in crop production?
    • Avoiding disease exposure or severe infection through timing or plant development
    • Developing immunity against every pathogen
    • Destroying all pathogens through genetic mutation
    • Increasing disease symptoms through environmental stress
11. What is the difference between disease resistance and disease tolerance?
    • Resistance reduces pathogen infection or multiplication, while tolerance reduces damage despite infection
    • Resistance and tolerance always mean complete immunity
    • Tolerance prevents pathogen entry, while resistance increases infection
    • Both terms refer only to seed dormancy
12. A short-day plant generally flowers when:
    • The uninterrupted night exceeds a critical duration
    • Daylight always exceeds 16 hours
    • Temperature remains below freezing
    • Soil moisture reaches its maximum level
13. What is vernalization in plant development?
    • Promotion of flowering by exposure to a prolonged period of low temperature
    • Promotion of flowering by continuous high temperature
    • Prevention of germination through seed drying
    • Induction of mutation through chemical treatment
14. What is seed dormancy?
    • A condition in which a viable seed fails to germinate under otherwise favourable conditions
    • The permanent death of an embryo
    • The immediate germination of every viable seed
    • The loss of genetic identity during storage
15. In a three-line cytoplasmic male sterility system, what is the main role of the maintainer line?
    • To maintain the male-sterile line without restoring pollen fertility
    • To restore fertility in every male-sterile plant
    • To produce pollen for all commercial crops
    • To eliminate cytoplasmic inheritance
16. What is the principal role of a restorer line in a three-line hybrid seed production system?
    • To restore pollen fertility in the resulting hybrid
    • To maintain male sterility in the female parent
    • To prevent seed formation in the hybrid
    • To eliminate the need for pollination
17. In mutation breeding, what does LD50 refer to?
    • The dose of a mutagen that causes 50% lethality in the treated material
    • The dose that produces 100% germination
    • The temperature that doubles chromosome number
    • The seed rate required for maximum yield
18. What is somatic hybridization in plant biotechnology?
    • Fusion of protoplasts from different plant cells to combine their genetic material
    • Crossing two pollen grains without female reproductive cells
    • Germination of seeds under artificial light
    • Selection of plants based only on visible height
19. What distinguishes genomic selection from conventional marker-assisted selection?
    • It uses genome-wide marker information to predict breeding values
    • It uses only one visible morphological character
    • It avoids genetic information completely
    • It selects plants only according to seed size
20. What is the main objective of speed breeding?
    • Accelerating crop generation cycles under controlled growing conditions
    • Increasing the time required for every crop generation
    • Preventing flowering in breeding populations
    • Replacing genetic evaluation with seed grading