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#1
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Difference in seed parent and pollen parent
Is there any different in an orchid if it's seed parent and pollen parent
are swapped with each other? That is what is the different to be the seed parent and to be a pollen parent? Thanks for the advice. |
#2
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Difference in seed parent and pollen parent
John wrote:
Is there any different in an orchid if it's seed parent and pollen parent are swapped with each other? I must be in a responsive mood... Yes. That is what is the different to be the seed parent and to be a pollen parent? Maybe I should elaborate... The pollen parent contributes mainly genomic DNA to the party. That is the DNA that is in the nucleus of the cell. However, there are cellular components (organelles) which have their own DNA. Chloroplasts (plastids) , and mitochondria both have their own (rather small) genome. The plastids and mitochondria are contributed (in addition to genomic DNA) by the female parent. If you were paying attention in genetics class, this is non-Mendelian inheritance. Same goes in animals by the way, except we don't have plastids. Mitochondrial DNA is maternally inherited. Sperm (or pollen) is smushed down small, for portability. Everything gets excluded except for the nuclear DNA. It is only the female gamete that is large enough to contain all of the other stuff that is necessary, like mitochondia and plastids. I don't know that mitochondrial DNA has that much affect on the orchid progeny (they are pretty much alike), but plastid DNA encodes for a lot of the color pigments. There are other more subtle differences between what the pollen and pod parent contribute, but that is the easiest to understand example. Rob -- Rob's Rules: http://www.msu.edu/~halgren 1) There is always room for one more orchid 2) There is always room for two more orchids 2a. See rule 1 3) When one has insufficient credit to purchase more orchids, obtain more credit |
#3
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Difference in seed parent and pollen parent
On Thu, 5 Jun 2003 22:49:09 +0800, "John" wrote:
Is there any different in an orchid if it's seed parent and pollen parent are swapped with each other? That is what is the different to be the seed parent and to be a pollen parent? Thanks for the advice. John, Below are some quotes (please accept my apology for the lack of attribution to many of them.) dealing with the subject In "classic" Mendelian genetics, both parents simply contribute genes to the progeny, and what the progeny ends up having depends on the dominance/recessiveness of various genes. This case works well for some traits, but there are other possibilities of co-dominance, incomplete dominance, or a trait being controlled by a set of genes as opposed to just one (human skin coloring is one of these traits, which causes children of mixed-racial heritage to usually look like a more-or-less even blend of the coloration of their parents). The niggle with "classic" Mendelian models is that they only work well when the two parents are the same species, or members of a complex of closely inter-related species. When you get into orchid breeding which mixes vastly different species (or even genera), the prospect of maternity of the plants begins to determine things more, because the genes are not the entire story of inheritance. In the maternal ova, the mix of proteins and other elements determines how those genes are actually applied to the plant. Hence, the maternal plant will often show a greater dominance of characteristics, especially when the plants are from disparate species or genera. Considering that you are trying to breed two Phal hybrids, which may very well be 50% or more the same, genetically, you will likely get a more Mendelian mix of traits. Were you to try, say, mating a big, white Cattleya as pollen parent with an Epi. conopseum as a pod parent, you would end up with a slightly larger, thicker, and lighter colored flower that still strongly resembles the Epi. conopseum parent. Many 1st-generation Epicatts show this in action, looking like a slightly modified version of their Epidendrum/Encyclia moms with the addition of coloration and some shape traits from their Cattleya dad. If we are talking only about traits linked to genes carried on the chromosomes of the parents, it doesn't matter which parent they come from. The capsule or pollen parent will contribute equally and neither will be more dominant in contributing specific traits, beyond the normal dominant/recessive characteristics of the genes involved. EXCEPT - many orchids are not simple diploids with 2 matched sets of chromosomes. If one of the parents is triploid, tetraploid, hexaploid, etc. it has MORE genetic material to contribute than a diploid counterpart and will have more influence on ALL traits. BUT - some characteristics are not determined entirely by genes on the chromosomes. Plastids and mitochondria also carry genes that contribute to photosynthesis, energy processing, and green and yellow color in flowers, for example. All plastids and mitochondria are contributed to the seed by the capsule parent, so certain characteristics such as light and temperature preferences, general vigor, and some flower colors may be more influenced by the capsule parent. Many breeders give anecdotal evidence of capsule or pollen parents being more dominant for certain characteristics in general, and they may be correct. I've just tried to list some of the understandable reasons why it may be true in particular cases. Pink x green = white Pink x white = green Cells don't have organs inside. They do have organelles, though. Anthocyanins accumulate in vacuoles. You can't simplify the site of accumulation of red pigments and yellow pigments. Both anthocyanins (red-purple-violet, etc) and chalcones (pale yellow) are flavonoids and carotenoids (orange-yellow, etc) are very different from the former. Carotenoids accumulate in chromoplasts, etc. the theory that mitochondria are responsible for certain pigment production in particular species. These organelles have their own genomes. This is why certain cattleyas are yellow, but their offspring are only yellow if that plant carries the pod. The mother is the only parent to pass on organelles. http://abstracts.aspb.org/pb2002/public/P73/1183.html Anthocyanin biosynthetic genes and flower color manipulation of Dendrobium orchids Additional Authors Kuehnle, Adelheid Champagne, Michele Affiliations: University of Hawaii Anthocyanins are one of the major pigments found in dendrobium flowers. A chemical survey of Dendrobium species and hybrids showed lavender cyanidin and peonidin to be the predominant anthocyanidin and orange pelargonidin to be rare. Our objective is to clone and characterize the key anthocyanin biosynthetic genes and to produce novel flower colors through genetic manipulation. Partial cDNA clones of chalcone synthase (CHS), flavonoid 3’5’ hydroxylase (F3’5’H) and a full clone of dihyroflavanol 4-reductase (DFR) were isolated using cDNA from floral buds of dark lavender Dendrobium Jaquelyn Thomas “Uniwai Prince”. Deduced amino acid sequences of CHS and DFR showed 84% and 90% similarity to those of the orchid, Bromheadia, respectively. Developmental expression profiles of infloresences showed that both DFR and CHS are expressed in all bud stages and decline to an undetectable level just before the flower opens. Contrary to DFR, CHS is expressed in leaves. The F3’5’H clone showed 67% identity to that of Petunia hybrida at the amino acid level. We have introduced the DFR gene from Antirrhinum Dendrobium with the intention of making novel colors of red shades. PCR and RT-PCR analyses indicated the presence and the expression of the introduced gene. Transgenic plants are already in the green house for flowering. |
#4
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Difference in seed parent and pollen parent
On Thu, 05 Jun 2003 11:34:46 -0400, Rob Halgren
wrote: John wrote: Is there any different in an orchid if it's seed parent and pollen parent are swapped with each other? I must be in a responsive mood... Yes. [snip cognizant reply] Rob, You are obviously considerably more knowledgeable and conversant on the subject of orchid genetics than me. Would you happen to be familiar with arcana of the inheritance of fragrance in orchids? I am attempting to hybridize reed-stem Epidendrums. The target phenotype is basically the typical reed-stem growth form, habit and hardiness with the addition of (day/night) fragrance, increased/inhanced flower size and form, and of course, new colors (blue?). Your example mentioned the female Epidendrums' iron-fisted dominance of plant and flower morphology. While color seems to be determined by both nuclear genetics and cyto ordinals, have you any idea of the mechanism of inheritance of fragrance? |
#5
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Difference in seed parent and pollen parent
You are obviously considerably more knowledgeable and conversant on the subject of orchid genetics than me. Would you happen to be familiar with arcana of the inheritance of fragrance in orchids? I don't have any unique tap into the fountain of wisdom. Or at least if I do I haven't figured out how to open it. I specialize in genomes and gene annotation. That means I know a little bit about a lot of things, and just enough to get me into trouble, but not out of it. I know nothing about fragrance though, so I won't go there. But, if anybody wants to do the 'Orchid Genome Project' (OGP), I'm your guy. I am attempting to hybridize reed-stem Epidendrums. The target phenotype is basically the typical reed-stem growth form, habit and hardiness with the addition of (day/night) fragrance, increased/inhanced flower size and form, and of course, new colors (blue?). Violet Blue? How much money you got? If you and a dozen of your friends contribute the cash equivalent of a compact car, I've always wanted to do that particular transgenic experiment. I have an idea about the genes in the biosynthetic pathway, but it costs money to isolate them and transduce them into orchids... Blue phalaenopsis might be neat too. I think it is a harder project to breed in blue the old fashioned way (but please try, I want some). Your example mentioned the female Epidendrums' iron-fisted dominance of plant and flower morphology. While color seems to be determined by both nuclear genetics and cyto ordinals, have you any idea of the mechanism of inheritance of fragrance? That wasn't my example... I have one though. From the few grexes I have grown out enough of, Phrag. schlimii (which smells like raspberries to me, but there is a genetic component on the sniffer end as well, I think) was capable of passing fragrance onto Hanne Popow, regardless of it being pod or pollen parent. That would imply nuclear, assuming that the grexes were labelled correctly. Take that as you will, it is certainly not a controlled experiment. If you know what genes are involved in fragrance biosynthesis in epidendrums, I can easily tell you where they are. Figuring out which genes is the hard part. -- Rob's Rules: http://www.msu.edu/~halgren 1) There is always room for one more orchid 2) There is always room for two more orchids 2a. See rule 1 3) When one has insufficient credit to purchase more orchids, obtain more credit |
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