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Tetraploid

Posted by frankiokc AR (My Page) on
Thu, Apr 27, 06 at 12:02

What does tetraploid mean? I have figured out what unifoliate is, but tetraploid has me stumped!
Franki in Hot Springs, AR


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RE: Tetraploid

I haven't got a clue! Seems like Greek to me! (maybe latin? LOL)

Here is a dictionary deffinition, Maybe it helps you out?

Diane

Here is a link that might be useful: Tetraploid


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RE: Tetraploid

  • Posted by jon_d Northern Calif. (My Page) on
    Thu, Apr 27, 06 at 15:51

Plants are normally diploid, meaning they have two chromosomes, that pair up in replication to make seeds. Tetraploids have double the number of chromosomes. Many hybrids are sterile because the diploid chromosomes don't match up properly with each other, being that they come from two different species. But, when doubled, by mutation, they can line up with the other matching one to make the plant viable. So, tetraploids are capable of producing seed, which produces plants nearly exactly like the parent. The best known example in gesneriads are the mini-sinningia hybrids like 'Cindyella', 'Dollbaby', and all the hundreds of hybrids produced from them. Back in the 60's these hybrids were first created by crossing the then, new, large flowered species, eumorpha with the tiny micromini species, pusilla and concinna. The two crosses made 'Dollbaby' and 'Cindy', both of which were completely sterile. They had no value in hybridizing and could only be propagated by removing and rooting crowns (the growth of foliage and flowers that arrise from the tuber). Then, by accident growers discovered mutants in propagations of first one and then the other. Tetraploids can be hard to spot, but they are generally larger in all aspects. So, the bigger foliage and flowers were what were first noticed. Then it was seen that they readily produced seed from self pollination. They were then used to produce many generations of hybrids, all of which were tetraploids. From a grower's standpoint, tetraploids can be more vigorous, have larger leaves and flowers, be more brittle, be a little hardier to cold, and be hairier. There are probably other characteristics; but, these come to mind.

Sometimes tetraploids are not desirable, such as in the mini strep hybrid 'Mighty Mouse'. A tetraploid version was found, and was very fertile, but it lost all of the miniature charm of the diploid hybrid. When tetraploids are crossed with diploids they usually produce hybrids of poor fertility, known as triploids, and the tetraploid dominates the cross. But it depends on the genus and family of plants we are talking about. In cymbidium orchids, many of the most beautiful and popular hybrids are triploids, which generally are sterile or nearly sterile.

There are also some tetraploid achimenes, but I don't know anything about them. I think Kartuz lists a bunch of these.

Jon


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RE: Tetraploid

Jon,

Thanks for the great explanation about tetraploids. I didn't understand why mini strep 'Mighty Mouse' isn't desirable because of its being a tetrapolid. Does it not have a nice growth habit? I like that it is mini, but I haven't seen it in person!

Franki


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