International Journal of Horticulture, 2017, Vol.7, No.22, 180-204
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Hybrids are manifested in various ways:
Increase in flower size and doubleness
Increase in number of flowers
Uniformity in size and maturity
Dwarf and compact
Free flowering and basal branching
Better resistance to drought, insect-pests and diseases
Better and wider adaptability to environmental conditions
7.1 Speciality of F
1
hybrids
Dwarf and compact growth with basal branching:
Petunia, Dianthus, Impatiens, Begonia, Geranium
Faster growth with longer growing season:
Petunia, Geranium
Doubleness : Petunia, Stocks, marigold, geranium
Tolerant to heat and humidity:
Begonia, Gerbera
Sterility: Marigold, Zinnia
Pot culture: Bougainvillea, Petunia, Pelargonium, Begonia
Free Flowering: Verbena, Marigold
Giant Flowers: Antirrhinum
Bedding plants with long blooming period:
Begonia semperflorens, Ageratum houstonianum
Cut flowers : Gerbera, Antirrhinum
Early appearance of first flower:
Pelargonium zonale, Anthurium scherzerianum
More number of flowers per season:
Bellis perennis
Hybrid varieties exploit both General Combining Ability (GCA) and Specific Combining Ability (SCA) through
utilization of heterosis. Single cross hybrids are more uniform than that of open pollinated, synthetic or composite
varieties. Production of hybrids is possible both in cross and self-pollinated crop species. Hybrid varieties are
maintained in the form of their parental inbreds.
There are various techniques used in production of hybrids.
Hand emasculation and hand pollination
: This technique is useful in hermaphrodite flowers and practiced
by skilled workers. e.g.
Pelargonium, Antirrhinum majus, Cyclamen persicum, Impatiens walleriana,
Dianthus caryophyllus, Salvia splendens
Hand emasculation and natural pollination:
Removal of male plants and pollination:
In dioecious species, male and female flowers are grown on
separate plants and the male plants are removed and only females are left. Desired male plants of the desired
variety are grown side by side to effect natural pollination. Seeds produced on female plants are harvested as
hybrid seeds.
Exploitation of male sterility
: It includes the use of cytoplasmic-genetic male sterility, genetic male sterility,
gametocidal sprays, and through the chemical suppression of male flower. It is used in zinnia, verbena,
marigold, rose etc. for F
1
hybrid seed production.
Use of self
-
incompatibility
: Self-incompatibility is applied for production of F
1
seeds in
Primula chinensis,
Petunia hybrida, Bellis perennis, Ageratum maxicum, Heliotrope ampervianum
, pansy etc.
Use of gametocide for chemical emasculation.
e.g. Sunflower
Use of marker genes to identify selfs to eliminate at seedling stage.
The first hybrid of double petunia was developed in Japan and later F1-hybrids were developed in ornamental
flowers in the Netherlands, Denmark, Germany, the USA and the UK. The few important hybrids were first
released in Petunia (in 1940-50); geranium single (1960); antirrhinum, pansy, marigold and zinnia (1965);
ageratum (1966); geranium double (1970); dianthus, impatiens and portulaca (1976-77); gerbera (1980) and
