A farmer purchased and planted F1 hybrid seed in 2022, resulting in a high-yielding and uniform crop. Pleased with the results, the farmer collected F2 seed from crossing the F1 plants (F1 x F1 cross) and planted this F2 seed in 2023. Based on our understanding of genetics, what outcome would we expect in terms of crop uniformity and yield in the F2 crop?

Question

A farmer purchased and planted F1 hybrid seed in 2022, resulting in a high-yielding and uniform crop. Pleased with the results, the farmer collected F2 seed from crossing the F1 plants (F1 x F1 cross) and planted this F2 seed in 2023. Based on our understanding of genetics, what outcome would we expect in terms of crop uniformity and yield in the F2 crop?

BlackTom AI · Accepted Answer

The question describes crossing F1 hybrid plants (F1 x F1) and harvesting the F2 seed, then planting it to observe future performance. This invokes basic Mendelian genetics about hybrids and segregation in the second filial generation.
Option 1: 'The crop will show improved uniformity and yield because all F2 plants will be homozygous.' This is incorrect because F2 plants from an F1 cross are not all homozygous; they segregate into a mix of genotypes (including heterozygotes) due to Mendel’s law of segregation. Uniformity and the specific yield traits are not guaranteed to improve in the F2.
Option 2: 'The crop will show reduced yield and uniformity due to genetic segregation in the F2 generation.' This statement matches the standard expectation: when crossing F1 hybrids, the F2 generation exhibits segregation of alleles, producing individuals with varied traits and often lower average yield compared to the uniform, high-performing F1 hybrid.
Option 3: 'The crop performance will remain consistent, as F1 hybrids maintain their characteristics in subsequent generations.' This is a common misconception. F1 hybrids do not inherently pass on the same uniform performance to the F2; the F2 tends to vary due to segregation and recombination, so consistency is not maintained.
Option 4: 'The crop will exhibit increased yield and uniformity due to continued genetic improvement in the F2 generation.' The idea of continued genetic improvement in the F2 from an F1 cross is not accurate in this context; without selective breeding over multiple generations and parental lines, the F2 is unlikely to exhibit increased uniformity and yield beyond the F1’s established performance.
In summary, the core concept is that F2 progeny derived from F1 hybrids show genetic segregation leading to a mix of phenotypes, reducing uniformity and often yield relative to the F1 hybrid, which is built to be uniform and high-performing due to heterozygosity and heterosis.

AGRI10051_2025_SM2 Supplementary or Special Exam: Genetics for Agriculture (AGRI10051_2025_SM2)- Requires Respondus LockDown Browser

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