Indian Society of Genetics & Plant Breeding


Flower pattern formation of orchids: Case studies with respect to ABCDE model

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Orchids are known for their beautiful flowers with
specialized organ identity and pattern formation. Genetic
models for pattern formation of flowers are well established
in actinomorphic flowers like Arabidopsis. However, the
orchid flowers show zygomorphic symmetry and contain a
highly differentiated labellum or lip. Besides, there is no
marked difference in terms of structures of sepals and petals
in many cases. The stamens and carpels are fused and
form the column or gynostemium with anther cap containing
pollinia at top. Few models like ‘Orchid code theory’,
‘Homeotic Orchid Tepal (HOT) model’, ‘P-code model’ etc.
have been proposed recently to explain genetic control of
flower patterning in orchids. We have studied the suitability
of those proposed models with some spontaneous bud
variants as well as somaclonal variants showing alteration
of floral organ patterns of all the flowers in the spike. The
basic model of flower development with some alteration
was found suitable in case of Cymbidium. Occurrence of
structural male sterility due to mutation in B class homeotic
gene in Cymbidium is also reported for the first time.The
“P-code” model of perianth formation in orchids was found
to be applicable for the recorded peloric mutants of
Phalaenopsis. Few other variants of Eria tomentosa,
Epidendrum sp. and Arundina graminifolia are also reported
here. Whether all these changes are due to alteration of
gene sequences or epigenetic mutations, needs to be
verified in details.

Keywords: Homeotic mutation, MADS-Box Genes, peloric mutations, perianth


Year: 2016
Volume: 76
Issue: 2
Article DOI: 10.5958/0975-6906.2016.00026.2
Print ISSN: 0019-5200
Online ISSN: 0975-6906


Ram Pal info_circle
N. Sailo info_circle
Raj Kumar info_circle
D. Barman info_circle
D. R. Singh info_circle

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