Orchid chromosomes and their behaviour in-vitro

Vij S.P., . (2005) Orchid chromosomes and their behaviour in-vitro. [Proceedings Paper]

Genotypic stability during growth and development depends upon regularly and ordered processes of chromosomal replication and segregation. Irregulaties in theses processes leading to chromosomal repatternings and gain/or loss of chromatin favour species diversification in plants like orchids which have ill-defined barriers of reproductive isolation. Chromosomal repatternings have been the most common mode of speciation in orchids with aneuploidy second; and polyploidy last. In the relatively less evolved and ground-growing orchid tribes Apostasieae. Cypripedieae Neottieae and Orchideae speciation has revolved around both numerical and structural changes in chromosome complements whereas in the more advanced and predominantly epiphytic Epidendreae structural repatternings have played major roles. The phenomenal rise of orchids in the international cut flower and pot-plant trade has been primarily due to the ease with which they respond to gene transfers across taxa hybrid embryo rescue and mass rapid propagation in-vitro. Genetic fidelity is highly desirable for commercial cultivation but cytological variations mitotic asynchrony selection of variant cells etc. often arise in tissue culture. We have been involved in testing the generative competence of Indian orchids in-vitro and the cyctological fidelity of the neo-formations. Our results suggest that donor tissues and growth stimuli influence the chromosomal make-up of the regenerants. Those from dermal tissues are cytologically stable whereas those from inner tissues often exhibit chromosomal aberrations. These aberrations result in malformed flowers and have a detrimental effect on commercial potential. Use of 2 4-D generally adds to their frequency. Occasionally BAP induces endo-reduplications in chromosomes. Even if variations are not conductive to maintaining uniformity in cut-flower production they add to the size of the gene pool and can be utilized in a variety of improvement programmes in the never-ending search for a more perfect orchid.

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Abstract

Genotypic stability during growth and development depends upon regularly and ordered processes of chromosomal replication and segregation. Irregulaties in theses processes leading to chromosomal repatternings and gain/or loss of chromatin favour species diversification in plants like orchids which have ill-defined barriers of reproductive isolation. Chromosomal repatternings have been the most common mode of speciation in orchids with aneuploidy second; and polyploidy last. In the relatively less evolved and ground-growing orchid tribes Apostasieae. Cypripedieae Neottieae and Orchideae speciation has revolved around both numerical and structural changes in chromosome complements whereas in the more advanced and predominantly epiphytic Epidendreae structural repatternings have played major roles. The phenomenal rise of orchids in the international cut flower and pot-plant trade has been primarily due to the ease with which they respond to gene transfers across taxa hybrid embryo rescue and mass rapid propagation in-vitro. Genetic fidelity is highly desirable for commercial cultivation but cytological variations mitotic asynchrony selection of variant cells etc. often arise in tissue culture. We have been involved in testing the generative competence of Indian orchids in-vitro and the cyctological fidelity of the neo-formations. Our results suggest that donor tissues and growth stimuli influence the chromosomal make-up of the regenerants. Those from dermal tissues are cytologically stable whereas those from inner tissues often exhibit chromosomal aberrations. These aberrations result in malformed flowers and have a detrimental effect on commercial potential. Use of 2 4-D generally adds to their frequency. Occasionally BAP induces endo-reduplications in chromosomes. Even if variations are not conductive to maintaining uniformity in cut-flower production they add to the size of the gene pool and can be utilized in a variety of improvement programmes in the never-ending search for a more perfect orchid.

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Item Type:	Proceedings Paper
Additional Information:	Summary En
AGROVOC Term:	ORCHIDACEAE
AGROVOC Term:	CHROMOSOMES
AGROVOC Term:	IN VITRO
Geographical Term:	MALAYSIA
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:28
URI:	http://webagris.upm.edu.my/id/eprint/16615

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