Practice question

Maize shows intermediate sensitivity to inbreeding because despite being predominantly wind-pollinated outbreeder, its genome contains moderate genetic load rather than extreme lethal equivalents seen in alfalfa. Experimental selfing by Shull and East early twentieth century revealed grain yield declining 30 to 50 percent over first three selfing generations, plant height reduced, ear size smaller and days to silking delayed due to exposure of recessive QTL controlling auxin and gibberellin pathways. However inbreds remain viable, fertile and maintainable allowing creation of inbred lines after six to eight generations of selfing with selection against weak types. Moderate depression enabled successful exploitation of heterosis through single cross hybrids producing 50 percent yield advantage over inbreds, foundational to modern maize improvement programs globally. 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.