International Journal of Horticulture, 2017, Vol.7, No.22, 180-204
189
Hasegawara = Cattleya ×Brassavola ×Broughtonia ×Laelia ×Sophronitis
Introgressive hybridization:
In this method, one species is completely replaced by another for example through
backcrossing. This is effective in orchids.
6.4 Breeding through hybridization in self-pollinated crops
Pedigree method:
In the pedigree method, individual plants are selected in F
2
for raising F
3
families of each
selection. Later on, in F
3
selection is made between and within the families. The variation within families tends to
become narrower in the subsequent F
4
and later generations while the differences among families ensure chances
of selection. The selection continues until F
6
or F
7
generations till the uniformity of all families is reached. This
method is useful in varietal development of primerose, aster, pelargonium, carnation and rose.
China aster cultivars: ‘Kamini’, ‘Poornima’, ‘Shasank’, ‘Violet’, ‘Cushion’
Hollyhock varieties: ‘Deepika’, ‘Dulhan’, ‘Gauri’, ‘Pusa Sweta’, ‘Pusa Krishna’, ‘Pusa Lalima’, ‘Pusa
Gulabi’
Marigold varieties: Pusa Basanti Gainda' (yellow coloured flowers) and 'Pusa Narangi Gainda' (orange
coloured flowers) have been developed through pedigree method.
Backcross method:
Backcross is the crossing of F
1
with either of the parents and test cross is the crossing of F
1
with recessive parents. This method is effective for breeding of disease resistance and for transferring male
sterility in ornamental crops. In Magnolia, ‘Yellow Bird’ has been developed by backcross method.
6.5 Breeding through hybridization in cross-pollinated crops
Single cross
(A x B): This is a cross between two inbreds such as A x B or C x D. A single cross is prepared by
planting two rows of female lines to one row of male line alternatively in such a way that two-third of the field
will produce hybrid seed for sale. In single crosses, maximum degree of hybrid vigour is manifested and reported
to produce uniform plants. Formula for number of single crosses is written as n (n-1)/2 where n=number of
inbreds. This method is utilized in gladiolus, chrysanthemum, dotted paeony.
Three way cross
(A x B) x C: In this case, a cross is made between a single cross used as female and an inbred
used as male. In this method, vigorous hybrid of first generation is used as female in order to get maximum yield
of hybrid seed. This method is used in chrysanthemum and orchids.
For example variety of rose
(
R. Wichuriana
× Floradora) × Debbie, Buccaneer a hybrid seedling of Golden
Rapture ×(Max Krause ×Capt. Thomas). In case of orchids, trigeneric hybrid
Brassolaeliocattleya (Brassavola
×Laelia ×Cattleya) and Mokara (Ascocentrum ×Vanda ×Arachnis
).
Double cross
(A x B) x (C x D):
It is the cross between two single crosses involving four different inbreds. A
double cross is made by alternate planting of two single cross plants in an isolated area and detasselling of the
single cross used as female parent. Double crosses are used for production of commercial hybrids. It is used
commercially in orchids,
Viola tricolor
and ornamental trees.
For example variety of rose 'Christian Dior' a cross between (Independence ×Happiness) ×(Peace ×Happiness).
In case of orchids tetrageneric hybrid Potinara (
Brassavola × Sophronitis × Laelia × Cattleya), and Robinara
(Aerides ×Ascocentrum ×Renanthera ×Vanda
) are some of the examples.
Top cross or inbred x variety cross
(A x Variety)
:
It is a cross between an open pollinated variety and inbred
line. It is employed in
Ageratum houstonianum, Bellis perennis, Gerbera jamesonii.
Composite cross:
Composites are advanced generation seed mixture of inter- varietal or inter-racial cross.
Synthetic cross:
A synthetic variety is produced based on the exploitation of additive genetic variance. In this
case, inbred lines, clones, mass selected varieties and lines developed by recurrent selection or reciprocal
