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Selective Breeding of Plants - HELP

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Selective Breeding of Plants - HELP

Postby BlondexSteph » Tue Mar 22, 2005 9:53 pm

What are the pros and cons in selective breeding for plants?




thank youu!
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Postby James » Tue Mar 22, 2005 11:21 pm

Pros: Ability to use highly desirable plant characteristics from a few organisms, and breed into one plant , and retain the favourable characteristics in furthur generations.

Cons: Inbreeding, where the gene pool is limited, leading to susceptibility to diseases and slight changes in the environment. Genetic diversity is reduced.
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Debut the cons

Postby BlondexSteph » Thu Mar 24, 2005 12:43 am

Any good comebacks for the cons for selective breeding of plants?
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Postby biostudent84 » Thu Mar 24, 2005 2:28 am

James wrote:Cons: Inbreeding, where the gene pool is limited, leading to susceptibility to diseases and slight changes in the environment. Genetic diversity is reduced.


I don't think inbreeding is possible in plants. Mendel messed around a LOT with the genealogy of his pea plants and never had an inbreeding problem.
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Re: Debut the cons

Postby biostudent84 » Thu Mar 24, 2005 2:31 am

BlondexSteph wrote:Any good comebacks for the cons for selective breeding of plants?


Whenever you get selective breeding, you have something choosing what is best for the population other than nature. Instead of natural selection, you get artificial selection.
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Postby mith » Thu Mar 24, 2005 3:16 am

Is selective breeding limited to breeding "like" plants? Wouldn't it also include breeding in hybrids for hybrid vigor?
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Postby biostudent84 » Thu Mar 24, 2005 3:59 am

mithrilhack wrote:Is selective breeding limited to breeding "like" plants? Wouldn't it also include breeding in hybrids for hybrid vigor?


The purpose of selective breeding is to isolate specific genes. The basic idea is to breed out any hybrids. For example...a flower can have either pink or white petals. Pink is dominant and white is recessive.

PP for homozygous dominant (pink)
Pp for heterozygous dominant (pink)
pp for homozygous recessive (white)

By the second definition of "hybrid," the Pp flowers are hybrids. Selective breeding makes the attempt to get rid of these hybrids and make all PP and pp flowers. That way, every time you breed a pink flower with a pink flower, it will ALWAYS yield a pink flower. Two white flowers will always yield a white flower regardless, so it isn't such a major point.

Hope this helps...
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Postby mith » Thu Mar 24, 2005 2:59 pm

I just looked it up on wikipedia and it seems to allow crossbreeding also.
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Postby DevGrp » Thu Mar 24, 2005 4:36 pm

Hybrids are also used to produce seeds. Often two different parents are crossed to produce the vareity you are after. The seeds are then called F1 hybrid seeds/plants. F1 hybrid plants are often sterile and any seeds obtained from these F1 plants often don't have the characterisitics that made the original F1 plants so desirable.To produce more seeds you need to cross the original parents. Selecting / breeding the parents to use is the tricky part.
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Postby biostudent84 » Thu Mar 24, 2005 8:44 pm

mithrilhack wrote:I just looked it up on wikipedia and it seems to allow crossbreeding also.


Um....yes? You can crossbreed if you want....but it's just going to make your job more difficult.

When you selective breed, you want to "purify" one specific gene or group of genes. Look back at the pink and white flowers. If you want all white flowers, it doesn't make sense to crossbreed your population with flowers carrying a gene for orange petals.
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Postby mith » Fri Mar 25, 2005 2:08 am

Well at times it's not as clear cut like in colors. For example if you wanted the best agricultural variety, ideally the plant should be resistant to diseases and produce high yield. Therefore you might need to selectively breed for both characteristics which might involve crossbreeding.
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Postby DevGrp » Tue May 03, 2005 7:52 pm

Didn't know this had carried on. F1 hybrids are very common in agriculture.
See http://www.humeseeds.com/hybrdlvr.htm

We are currently working on a medicinal plant and some one has spent 10 years developing a hybrid that has much higher drug levels than normal plants. Sadly if you interbreed that plant you lose over 20% of the drug level per generation so in this case its important to always go back and produce more F1 seeds.
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