Explain the technique of cross-hybridization in plant breeding, including the purpose of emasculation and bagging.

Question

Accepted Answer

Concept understanding — Hybridization (Plant Breeding Technique)

Hybridization is the chief and most productive method of plant breeding, because it is the only reliable way to combine the desirable characters of two or more different varieties into one new genetic combination while also exploiting hybrid vigour (heterosis) — the extra vigour or yield a hybrid can show over both its parents. The programme runs as a defined sequence: collecting variability (assembling a germplasm collection of wild relatives and other varieties, conserved either in situ in forests/reserves or ex situ in botanical gardens and seed banks); evaluating and selecting parents with complementary desirable traits and self-pollinating each for three to four generations to make it homozygous; hybridization proper, in which the superior variety becomes the female (recurrent) parent, is emasculated, and is artificially cross-pollinated with pollen from the male (donor) parent, then bagged and tagged, producing the F1 hybrid generation (crosses may be intravarietal, intervarietal, interspecific or intergeneric — the latter two, between more distantly related plants, being called wide or distant crosses); selection and testing of the superior F1 recombinants, self-pollinated further until the desirable traits become homozygous and stop segregating; and finally testing, release and commercialisation, after field trials across several seasons and agro-climatic zones. Hybridization is what produced the Green Revolution's semi-dwarf wheat (Sonalika, Kalyan Sona) and semi-dwarf rice (Jaya, Padma, Ratna, derived from IR8 and Taichung Native-1), the high-sugar, thick-stemmed sugarcane varieties CO-419/421/453 (from crossing Saccharum barberi and S. officinarum), and hybrid millets such as maize Ganga-3, jowar CO-12 and bajra Niphad; the same underlying technique is also used to breed for disease resistance (e.g. Himgiri wheat, Pusa Swarnim Brassica) and insect-pest resistance (e.g. Pusa Gaurav Brassica, Pusa Sawani okra), by selecting specifically for those traits within the same hybridization-and-selection cycle.

Cross-hybridization is the technique of cross-pollinating two selected parent plants, each strong in a different desired trait, so that their traits combine in the resulting hybrid offspring. Carrying this out under control, in a bisexual flower chosen as the female parent, requires two supporting steps. Emasculation is the careful removal of the flower's own anthers before they mature and shed pollen, which prevents the flower from fertilising itself with its own pollen. Once emasculated, the flower is bagged -- covered to physically exclude any other, wind- or insect-carried pollen -- until the breeder is ready to apply, by hand, pollen collected specifically from the chosen male parent (artificial pollination), after which the flower is re-bagged until the cross has successfully set seed. Together, these steps ensure that the seed produced is a genuine hybrid between the two intended parents, and not an accidental self-pollination or a cross with an unplanned, unknown pollen source.

[!ANSWER]

Cross-hybridization = cross-pollinating two selected parents to combine their traits; emasculation = removing the female parent's own anthers to prevent self-pollination; bagging = covering the emasculated flower to exclude foreign pollen until the breeder applies the chosen male parent's pollen.

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2025Set ANNUAL2 marks
$Q. What is Heterosis?$
›Reveal solutionSolution

Heterosis is the superiority of an F1 hybrid over its parents, exploited in plant/animal breeding.

Heterosis, also called hybrid vigour, is the phenomenon observed in plant and animal breeding where crossing two genetically dissimilar (often inbred) parental lines produces an F1 hybrid offspring that is superior to both parents in one or more desirable characteristics — such as higher yield, better growth rate, larger size, or greater disease resistance. This superiority is generally attributed to the increased heterozygosity in the hybrid, masking deleterious recessive alleles and combining favourable dominant alleles from both parents. Heterosis is widely exploited commercially, e.g. in hybrid maize, and the hybrid seeds are usually produced fresh each generation because the beneficial heterozygous combination is not maintained upon further self- or inter-breeding.

✓Final answer
$Heterosis: the F1 hybrid's superiority over both parents in yield/vigour/resistance, arising from increased heterozygosity.$
CBSE 2020Set OC_BOTANY2 marks
$Q. Define hybridization. Name the different types of hybridization.$
›Reveal solutionSolution
Hybridization is the deliberate crossing of genetically different parents to combine desirable traits in their offspring, and is classified as intervarietal, interspecific, or intergeneric depending on how closely related the parents are.

Definition

In plant breeding, hybridization refers to crossing two selected plants having genetically dissimilar traits so that their good characters (e.g. high yield, disease resistance, quality) are combined in the resulting hybrid progeny. The hybrids are then selected and stabilised through further breeding.

Types of hybridization

Intervarietal hybridization (intraspecific) — parents are two different varieties/strains of the SAME species.

Interspecific hybridization — parents belong to two different species of the SAME genus.

Intergeneric hybridization — parents belong to two different genera altogether (relatively rare, harder to achieve due to greater genetic distance).

Significance

Hybridization is a fundamental tool in classical plant breeding used to develop new, improved varieties combining traits such as high yield and disease/pest resistance, and remains the basis of many high-yielding varieties developed during the Green Revolution.

✓Final answer
$Hybridization is the crossing of genetically dissimilar plants to combine desirable traits; its types are intervarietal, interspecific, and intergeneric hybridization.$

[!ANSWER]
Cross-hybridization = cross-pollinating two selected parents to combine their traits; emasculation = removing the female parent's own anthers to prevent self-pollination; bagging = covering the emasculated flower to exclude foreign pollen until the breeder applies the chosen male parent's pollen.

Q.Explain the technique of cross-hybridization in plant breeding, including the purpose of emasculation and bagging.

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