International Journal of Horticulture, 2017, Vol.7, No.22, 180-204
184
Here the style length is governed by two independent loci, S and M. All these three stylar types are self
incompatible but cross compatible.
Geitonogamy:
When the pollen grains of a flower fall on the stigmas of another flower on the same plant, it is
called as geitonogamy and it is genetically equivalent to self-pollination. e.g Periwinkle, Salvia.
Often Cross Pollination
: In some crops, cross pollination exceeds 5% even upto 30% and genetically
intermediate between self and cross pollinated crops.
4 Objectives of Breeding for Different Ornamentals
Development of tetraploids and triploids in marigold, verbena, amaranth etc produce bigger size and long lasting
flowers. In roses, varieties with shapely buds and longer stems are required for export purpose. Varieties with
longer flower duration may be developed in case of
Rosa damascena, Rosa bourboniana.
In gladiolus, efforts
should be made to develop fragrant varieties with other desirable traits. In chrysanthemum, there is need for
development of photo-insensitive varieties in different types. Hybrid cultivars in ornamentals are appreciated
mostly for their uniformity, shape, size, dwarfness, colour etc. In India, breeding of F
1
and F
2
hybrids of different
annual and biennial flowers which have great potential in view of superiority over open pollinated cultivars in
many characteristics.
4.1 Breeding standards for seed propagated ornamentals
Breeding methods for ornamental plant breeding range from traditional selection breeding to modern
biotechnology and genetic engineering. Conventional plant breeding results into development of a number of
open pollinated varieties or F
1
hybrids in ornamental plants over the last decades with the objectives for
improvement of yield and quality and extension of growing season. Utilization of polyploidy both
auto-polyploidy from spontaneous or induced chromosome doubling and allo-polyploidy from spontaneous or
artificial inter-specific hybridization is widely used among ornamentals to rapidly combine traits and to create
giant type of flowers and leaves. In seed propagated ornamentals, with a considerable seed market, cultivars
should normally be bred as hybrids based on inbred parental lines. In most cases seed prize can support hybrid
seed production through manual emasculation and pollination among parentals (
Begonia semperflorens
,
Cyclamen
spp.,
Pelargonium
spp.,
Petunia
spp.,
Primula
spp.,
Viola
spp.).
4.2 Breeding standards for vegetatively propagated ornamentals
In vegetatively propagated ornamentals, inter-specific hybridization has been performed to an extent that
traditional classification into botanical species is impossible (roses, orchids etc). Breeding schemes in such cases
simply consists of hybridization followed by selection among cloned seed offspring to identify new useful clones.
Systematic breeding for new improved clones in such species normally depends upon international agreements to
protect breeders rights for the new cloned cultivars.
4.3 Scope of advance breeding techniques
Present floriculture scenario is dominated by for flowers with novel traits. The development of new tools for
introducing foreign genes into plants in combination with growing knowledge and technology related to gene
identification and isolation have enabled the specific alteration of single traits in an otherwise successful cultivars
and have broadened the available gene pool of a given species. There is a large scope for improvement of
floricultural crops using biotechnological tools like micropropagation,
in vitro
mutagenesis, somaclonal variation,
embryo recovery, haploid culture, protoplast fusion, genetic transformation and DNA finger printing. The new
strategies of
in vitro
culture have been commercially implemented for the propagation and breeding of a wide
variety of ornamental crops. Nowadays, there are a number of cultivars obtained directly or indirectly by the use
of induced
in vivo
mutation. Embryo recovery is effective in inter-specific or inter-generic crosses is to transfer
alleles for disease resistance, environmental stress tolerance, high yield potential or other desirable characteristics
of species or genus to accepted cultivars, to recover rare hybrids derived from incompatible crosses as well as to
