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#selfing

3 public questions tagged with this topic.

Plant Breeding 2

Selfing reduces heterozygosity by:

Selfing systematically reduces heterozygosity because segregation from heterozygous parent yields one quarter AA, one half Aa, one quarter aa. Only half offspring remain heterozygous, halving H each generation. Formal relationship Ht equals H zero times one half to power t, where t number selfing generations, independent of allele frequencies for loci not under selection. After first selfing heterozygosity 50 percent, after second 25 percent, after six cycles about 1.6 percent. Inbreeding coefficient F rises reciprocally approaching 0.99 after six generations. This principle underpins extraction of recombinant inbred lines by single seed descent, development of near-isogenic lines and fixation of transgenes. Prediction allows breeders to schedule required selfing generations to achieve sufficient homozygosity for varietal stability and DUS testing. 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.

Ref: Hartl & Clark Principles Population Genetics selfing reduction; Falconer Introduction Quantitative Genetics; NCBI Bookshelf Heterozygosity equation.

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Plant Breeding 1

Reduced vigor due to repeated selfing is known as:

Inbreeding depression emerges as phenotypic deterioration in vigor, height, fecundity and stress tolerance following repeated selfing of naturally outcrossing species. Underlying genetic architecture includes dominance hypothesis: many loci carry partially recessive deleterious mutations in genes governing chlorophyll biosynthesis, auxin transport, root elongation and defense signaling. Increased homozygosity makes these recessives expressed, reducing enzyme activity and hormone levels. Pseudo-overdominance where two linked loci in repulsion mimic overdominance also contributes. Quantitative studies in maize reveal hundreds of loci with small negative dominance effects cumulating to yield loss. Because self-pollinated crops have purged much load historically through natural selfing, their depression minimal compared to cross-pollinated species where load sheltered in heterozygotes, making management critical for hybrid breeding. 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.

Ref: Charlesworth & Willis Annu Rev Ecol Inbreeding depression; Falconer Quantitative Genetics; Singh BD Inbreeding depression cause.

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Plant Breeding 1

Repeated selfing leads to:

Repeated self-fertilization progressively eliminates heterozygosity because each heterozygous locus segregates 1 AA:2 Aa:1 aa, only half progeny retain heterozygosity. Mathematically heterozygosity after t generations Ht equals H0 multiplied by one-half raised to power t, so after seven generations approximately 0.8 percent remains. Continuous inbreeding drives allele fixation toward homozygous states, exposing recessive homozygotes for selection. In breeding this rapid homozygosization underlies development of pure lines, recombinant inbred lines for QTL mapping and near-isogenic lines via repeated backcross selfing. While genetic uniformity achieved, fitness may decline if deleterious alleles uncovered, necessitating concurrent selection against weak segregants to identify vigorous homozygotes retaining yield potential and adaptation. 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. Additional insights from genomic studies reveal QTL clusters, epigenetic modifications and protein interactions that influence trait expression under varied agro-climatic conditions and management.

Ref: Allard Principles Plant Breeding homozygosity; Hartl & Clark Population Genetics selfing equation; Falconer Quantitative Genetics.

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