International Journal of Horticulture, 2017, Vol.7, No.22, 180-204
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Synthetic seed:
It is the encapsulated somatic embryos which functions as mimic seeds and develops into
seedlings under suitable environmental conditions. It may be encapsulated bulb, bud or any form of meristems. In
addition to somatic embryos, axillary buds, adventitious buds, shoot tips and protocorms are also used to produce
synthetic seeds. Synthetic seeds are reported in orchid,
Dianthus, Lilium, Pelargonium
.
Genetic transformation in ornamental plants:
Genetic
transformation is the transfer or introduction of a DNA
sequence or, more specifically, of a gene to an organism without fertilization or crossing. The genetically
transformed plants are called transgenic plants. Genetic introduction is the controlled introduction of nucleic
acids in a receiver genome without fertilization.
Different genetic transformation techniques have been established with the development of tissue culture
techniques and genetic engineering which include the use of
Agrobacterium tumefaciens
, particle acceleration
(biolistics), polyethylenoglicol, electroporation, sinication, silica carbonate microparticles, microlaser, micro and
macro-injection and direct DNA application.
During 90’s, first transgenic petunia was developed. Among major cut flower crops, rose, chrysanthemum and
carnation all have been genetically transformed.
Rosa hybrida
cv. ‘Royalty’ has been transformed by
co-cultivation of
Agrobacterium
and friable embryogenic callus followed by embryogenesis to recover
transformed plants.
Chrysanthemum indicum
and
Chrysanthemum grandiflora
both have been transformed by
Agrobacterium
infection of either leaves which regenerated transformed plants by organogenesis or peduncle which formed
transformed callus capable of regenerating transformed plants.Transformed
Dianthus caryophyllus
(carnation)
cultivars have been produced by co-cultivation of leaves, petals, or stems with
Agrobacterium
followed by direct
or indirect organogenesis. Besides,
Agrobacterium
mediated transformation has also been reported in
Narcissus,
Gladiolus, Lilium longiflorum, L. leichlnii var. maximowiczii
and
Tulipa
. In addition to these floral crops, the
following flower crops have been tried for transformation. These are
Gerbera, Dendrobium, Antirrhinum,
Anthurium, Eustoma and Pelargonium.
Molecular breeding of ornamental crops for various approaches:
The first successful application of genetic
engineering for flower colour modification was petunia to produce crimson coloured pelargonidin pigments by
transferring Al gene from
Zea mays
which codes for a specific protein dihydroquercetin-4-reductase (DQR). The
first antisense technology has been used genetically engineered petunia to incorporate antisense Chs gene
(Chalcone Synthase gene) to alter flower colour. Blue carnation is developed through characterization of
anthocyanin and use of anti-sense suppression to block the expression of a gene encoding Flavonone
-3-hydrogenase. In antirrhinum, novel yellow colour has been tried with genetic modification of chalcone and
aurone flavanoid biosynthesis. Florigene was one of the first companies to obtain an alteration of colour by
genetic engineering. Working together with chrysanthemum breeder
Fides
,
Florigene
has transformed the pink
chrysanthemum variety 'Moneymaker' into a white flower, by blocking the
chalcone synthase
gene responsible
for pigment synthesis.
Genetic engineering is also applied to increase the vase life of flowers, by blocking the ethylene production of
flowers. Ethylene triggers flower deterioration.
DNA---Finger Printing:
DNA---Finger Printing is a technique used to distinguish between individuals of the
same species using only samples of their DNA. DNA profiling exploits highly variable repeat sequences called
Variable Number Tandem Repeats. These loci are variable enough that two unrelated humans are unlikely to
have the same alleles.
RFLP (Restriction Fragment Length Polymorphism)
analysis is found to be useful for estimating genetic diversity,
to assist in the conservation of endangered species and plant genetic resources. It is also used for plant genome
