Heterosis, used in hybrid cultivars, refers to which phenomenon and why it is exploited?

• A. Random mating leads to unpredictable traits
• B. Superior performance of hybrids over inbred parents, used to increase yield, vigor, and uniformity; requires production of hybrid seed and cross-pollination
• C. A decrease in vigor in hybrid lines
• D. The fixation of recessive traits in the population

Answer: (B)

Heterosis, or hybrid vigor, is the phenomenon where crossing genetically distinct lines produces offspring that outperform their inbred parents in traits like yield, vigor, and uniformity. This advantage is why breeders create hybrid cultivars and rely on cross-pollination and hybrid seed production to achieve consistent, high-performing crops. The improved performance comes from non-additive gene action, where heterozygous combinations can mask deleterious recessives and exhibit superior traits. Other ideas don’t fit because random mating doesn’t reliably give superior hybrids, a decrease in vigor describes inbreeding depression, and fixation of recessive traits is a result of inbreeding rather than heterosis.