#self-pollination

Plant Breeding 3

A pure line originates from:

Pure line originates from single homozygous plant that through repeated selfing becomes genetically uniform with homozygosity exceeding 99 percent across genome. Starting material may be landrace mixture, segregating population or single heterozygote, but after several generations of single plant selection and self-pollination, locus fixation occurs according to Ht equals H0 half to power t. Johannsen using Phaseolus vulgaris demonstrated selection within resulting pure line does not shift phenotype because variation purely environmental. Molecular markers such as SSR show monomorphic profile within line. Concept fundamental to pedigree method where F2 individual selected and advanced by selfing until F6 to extract superior pure line for evaluation. Pure line provides stable genotype preserving adapted gene complexes and serves as parent for hybrids and multiline blends. 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: Johannsen W 1903 Erblichkeit pure lines; Acquaah Definition pure line origin; Singh BD Origin pure line single homozygous plant.

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Plant Breeding 2

Inbreeding depression is highest in:

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.

Ref: Allard Principles Plant Breeding mating system depression; Nature Reviews Inbreeding in crops; Singh BD classification cross vs self.

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Plant Breeding 1

Removal of stamens to prevent self-pollination is called:

Emasculation removes immature androecium to render female parent incapable of self-pollination, ensuring only desired male parent contributes pollen in artificial cross. Techniques include manual method using forceps and scalpel to excise anthers before dehiscence at green bud stage, hot water emersion at 42 to 48C for 5 to 10 minutes to kill pollen in rice and sorghum exploiting differential thermo-sensitivity, and suction method aspirating anthers. After removal, flower covered immediately with butter-paper bag to exclude foreign pollen. Stigma bagged separately until receptive, indicated by feathery, sticky exudate secretion. Pollination performed next morning with freshly collected pollen rich in borate and calcium for tube growth. Emasculation increases hybridization success and hybrid purity essential for genetic studies and commercial seed production. 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: Acquaah Plant Breeding Emasculation techniques; IARI Practical Manual Hybridization steps; e-coursesonline.iasri.res.in Emasculation.

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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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Plant Breeding 1

Cleistogamy promotes:

Cleistogamy represents floral syndrome where flowers remain closed throughout anthesis, perianth never unfolding, thus anther dehiscence occurs inside bud envelope and pollen deposited directly onto adjacent stigma. Controlled by genes regulating lodicule expansion, corolla opening and jasmonic acid signaling affecting anther elongation. In cleistogamous rice mutant cl7 and barley cly1, suppression of petal opening enforced by mutation in AP2 transcription factor. Consequence obligate self-pollination ensuring seed set under rain or low pollinator activity, protecting pollen from desiccation and pathogens. For biotechnology, cleistogamy used as biological confinement for transgenes preventing gene flow, while drawback reduced genetic variability and limited scope for recombination-driven improvement. 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: Lord EM Cleistogamy Encyclopedia; PubMed Rice cleistogamous cl7 gene; Campbell Biology pollination control.

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Sexual Reproduction in flowering Plants

Which of the following plants produces both chasmogamous and cleistogamous flowers, and what is the primary advantage of

Plants like *Commelina*, *Viola* (Common pansy), and *Oxalis* produce both types. Cleistogamous flowers do not open at all. Their advantage is an assured seed set even in the absence of pollinators, as they are invariably autogamous.

Ref: Image of a Commelina or Viola plant showing open flowers above ground and closed flowers underground.

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Sexual Reproduction in flowering Plants

Autogamy is genetically similar to which other form of pollination, and why?

Autogamy is self-pollination within the same flower. Geitonogamy is pollination between different flowers of the *same* plant. Genetically, both are forms of self-pollination because the pollen comes from the same genetic individual (genet), even if Geitonogamy is functionally cross-pollination requiring an agent.

Ref: Comparison diagram of Autogamy (same flower), Geitonogamy (same plant, different flower), and Xenogamy (different plant).

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