66 public questions tagged with this topic.
Pomato is formed by the fusion of protoplasts from tomato and potato plants through somatic hybridization. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Biology - Zoology portion covering relevant system and function.
Comprehensive identification of somaclones demands multi-level screening, since variation manifests from visible morphology to DNA sequence. Whole-plant evaluation in greenhouse notes leaf shape, plant height, flowering time, flower color, and vigor, providing first indication of off-types. Cytological examination extends analysis to nuclear level, measuring chromosome number, polyploidy, anaphase bridges, and micronuclei after fixation and acetocarmine staining of actively dividing root tips. Molecular level assessment employs electrophoretic tools: isozyme SDS-PAGE reveals altered enzyme mob
Ref: Bhojwani & Dantu Plant Tissue Culture Ch 12 detection; NCBI PMC403111 somaclonal markers; IntechOpen Molecular electrophoresis; https://www.ncbi.nlm.nih.gov/books/NBK218342/
Plant growth regulators drive developmental plasticity in vitro, and prolonged exposure creates reversible adaptive responses rather than permanent DNA changes. High levels of synthetic auxins like 2,4-D and cytokinins such as BAP increase endogenous hormone synthesis, alter receptor sensitivity, and remodel chromatin through changes in DNA methylation and histone acetylation. Cells become habituated, growing without external hormones, show vitrification with water-soaked translucent appearance, or lose morphogenetic competence. Such phenotypes affect culture behavior, shoot regeneration frequ
Ref: Alberts Molecular Biology of Cell 6th ed Ch 21 Plant tissue culture; NCERT Biology XII Unit 9; NCBI Bookshelf NBK218342 somaclonal variation physiology and habituation.
Gynogenesis differs from androgenesis because it uses female gametophyte components unfertilized ovules ovaries or embryo sacs as explant source rather than anther pollen. In gynogenesis egg cell synergid or antipodal cells within embryo sac are induced to develop sporophytically into haploid embryo without fertilization, typically by culturing unpollinated ovaries or ovules on sucrose enriched medium with auxin cytokinin combination. Female gametophyte origin ensures captured genome is that of maternal parent, contrasting with androgenesis capturing paternal genome from microspores. Gynogenes
Ref: Yang & Zhou Theor Appl Genet gynogenesis; Bohanec 2009 haploid production review.
Androgenesis results in plants whose nuclear genetic constitution is identical to male parent gamete contribution because development originates from male gametophyte microspore. Microspores formed after meiosis in anther tapetum carry recombined haploid genome representing segregation products of diploid male parent heterozygous loci. Under stress pretreatment cold starvation heat and culture conditions gametophytic program that would normally produce mature binucleate pollen with vegetative generative cells is aborted, sporophytic pathway triggered leading to repeated mitotic divisions formi
Ref: Guha & Maheshwari 1964 androgenesis; Touraev et al., Trends Plant Sci microspore embryogenesis.
Gene pyramiding, also called gene stacking, assembles multiple favorable alleles, often for disease or insect resistance, into single elite genotype to achieve broader spectrum, durable, and synergistic protection. Unlike single gene deployment that is vulnerable to pathogen race evolution breaking resistance within few seasons due to simple mutation, combining two to four unlinked major resistance genes forces pathogen to acquire multiple virulence mutations simultaneously, which is epidemiologically rare and fitness costly. Example includes stacking bacterial blight genes Xa4, xa5, xa13, Xa2
Ref: Sanchez AC et al. 2000 – Gene pyramiding multiple genes concept; Sundaram et al. Rice bacterial blight pyramiding
Linkage drag describes physical association along chromosome between desired donor gene and neighboring deleterious or undesirable genes inherited together due to limited recombination near centromere or introgression segment. When donor parent contributes disease resistance gene for example, flanking chromosomal region spanning several megabases containing genes for poor quality, late maturity, low yield, or bitterness is co-transferred because crossing over between closely linked loci is rare per meiosis, frequency proportional to map distance in centimorgans. Until recombination breaks link
Ref: Hospital F. Linkage drag – theoretical; Young & Tanksley 1989 RFLP study of drag. Nature Biotechnology
Marker-assisted selection replaces unreliable phenotypic screening with direct interrogation of DNA sequence polymorphisms linked to trait-controlling loci. Instead of measuring disease severity in field that depends on weather and inoculum load, MAS uses polymerase chain reaction amplification of SSR, SNP, or SCAR markers situated within few centimorgans of target gene, detecting presence of donor allele regardless of environment, plant stage, or dominance interactions. Segregating individuals are genotyped at seedling stage, selection made before flowering, accelerating backcross programs an
Ref: Tanksley SD 1989 BioTechnology – RFLP; Collard & Mackill 2008 Philos Trans – MAS based on DNA markers
Gynogenesis derives haploid plants from female gametic lineage, typically through in vitro culture of unpollinated ovules, ovaries, or isolated embryo sacs under defined media conditions. Under specific culture conditions, cells of embryo sac such as egg cell, synergids, antipodals, or nucellar tissue undergo sporophytic development without fertilization, forming haploid embryo with maternal genome and maternal cytoplasm. Unlike androgenesis that samples male gametes, gynogenesis recovers maternal genotype useful when male gametophyte is recalcitrant or expresses self-incompatibility leading t
Ref: Hosoki T & Asahira. Gynogenesis – ovule culture; Bohanec B 2009 – review of gynogenic haploid breeding
Androgenesis is male gametophyte-mediated haploid production pathway exploiting totipotency of immature pollen. Anthers containing uninucleate microspores at late uninucleate to early binucleate stage are excised and cultured on nutrient media, or isolated microspores are separated from anthers and cultured in liquid medium under stress. Developmental program of microspore shifts from pollen grain maturation toward sporophytic division, forming embryo-like structures or callus that regenerate haploid plantlets with n chromosomes derived entirely from paternal gametic genotype. Process exploits
Ref: Seguí-Simarro JM. Androgenesis review 2010 J Exp Bot; Maluszynski et al. FAO Haploid protocols – anther culture
Conventional pedigree inbreeding reduces heterozygosity by half each selfing generation, requiring F6-F7 to attain >98% homozygosity, a process taking 5-6 years. Doubled haploid approach collapses this timeline to single step through manipulation of gametic pathway. Haploid plant carrying n chromosomes is induced via anther culture, isolated microspore culture, ovule culture, or wide hybridization-induced chromosome elimination such as wheat × maize system. Haploid set containing single allele per locus is then doubled chemically with colchicine or spontaneously through endomitosis, producing
Ref: Snape JW. Doubled haploid breeding; Dwivedi et al. 2015 – One-generation homozygosity review
Doubled haploid lines are produced from haploid plants by chromosome doubling, resulting in individuals where both chromosome sets are identical copies, achieving immediate complete homozygosity at every locus without residual heterozygosity or segregation. Genotypic value is fully fixed, allelic pairs AA or aa across genome, eliminating segregation in progeny and exposing recessive alleles. This purity is valuable because phenotype directly reflects genotype, dominance effects removed, deleterious recessives exposed for purging, and additive variance accurately estimated without dominance noi
Ref: Forster BP et al. 2007 – DH advantages. Germanà MA. Haploids and doubled haploids in crop improvement
