Genetics, Plant Breeding, and Seed Technology
Genetics, Plant Breeding and Seed Technology tests inheritance, breeding methods and seed quality. The exam links genotype and phenotype, selection and hybridization, and seed certification with field performance.
Core rules
- A gene is a hereditary unit; alleles are alternative forms. Genotype is the genetic constitution; phenotype is the observable expression after environment interacts with genotype.
- Mendel's law of segregation explains the 3:1 phenotypic ratio in a monohybrid F2. A test cross uses a homozygous recessive parent to reveal the genotype of a dominant phenotype.
- Self-pollinated crops are often improved by pure-line selection and hybridization. Cross-pollinated crops need population approaches and isolation to prevent unwanted pollen.
- Seed certification checks varietal identity, purity, germination, moisture and health. Pure live seed (PLS) = purity % × germination % ÷ 100.
Worked example
A seed lot has 98% purity and 90% germination. PLS = 0.98 × 0.90 × 100 = 88.2%. If the recommendation is 100 kg of pure live seed per hectare, bulk seed needed = 100 ÷ 0.882 = 113.4 kg/ha. Reasoning: purity and germination multiply because both must be satisfactory. The adjustment prevents under-seeding when the lot contains inert matter or dead seed.
Traps that cost marks
Do not use phenotype to infer genotype without a test cross. Do not confuse backcross with test cross. Do not treat certification as a guarantee of high yield; it certifies seed quality and identity. Do not add purity and germination. In breeding questions, match the method to the pollination system and the crop's multiplication rate.