Practice question

Magnitude of inbreeding depression correlates inversely with natural selfing rate. Cross-pollinated crops like alfalfa Medicago sativa, carrot Daucus carota and squash Cucurbita pepo naturally outbreed, maintaining high heterozygosity and sheltering many recessive deleterious mutations protected from selection. Forced selfing uncovers this hidden load causing severe biomass reduction, flower abortion and sometimes lethality. Self-pollinated crops like wheat, rice and chickpea evolved under chronic selfing, exposing recessive alleles each generation and allowing purging selection to eliminate severe variants, leaving minimal residual load. Apomictic and vegetatively propagated species circumvent inbreeding via clonal maintenance, thus depression absent. Knowledge of depression level guides breeding method choice: recurrent selection for outbreeders versus pure line selection for selfers, influencing mating design and conservation strategies. This understanding supports competitive exam preparation for NEET, GATE and CSIR NET concepts linking genotype with phenotype through molecular pathways involving transcription factors, hormones and metabolic enzymes that regulate development, adaptation and reproductive biology in applied breeding programs.