Crossing two var. albas - Orchid Board

Undergrounder · #1 11-09-2008, 06:32 AM

If i cross two different Phal. violacea var. albas, will all of the seedlings be alba, or will i get a mix? And if i get a mix can i expect half? a quarter? three quarters? to be alba?

Brooke · #2 11-09-2008, 08:24 AM

I can't give you the percentages that will be alba but you will get some that are different because of the recessive genes in the vio.

Brooke

kavanaru · #3 11-09-2008, 08:59 AM

it depends onhow "clean" your two albas are... but if you keep crossing albas for several generation, you will get to a point of 100% albas...

camille1585 · #4 11-09-2008, 09:30 AM

There is no way of knowing the expected proportion of albas in the progeny without knowing the two plants genotypes. It depends on the alleles of the gene(s) involved. For example if your parents are AA x AA or aa x aa, then their progeny will be 100% indentical to the parents.
But if you have heterozygous plants and you cross them (Aa x Aa) for example, you will get a mix of albas and other colors. In that case normally there will be a greater proportion of the parental genotypes (alba) than other colors in the progeny. But that only works if there is only one gene responsible for the alba color. If there are interactions between genes, the proportion of albas in the offspring can differ widely!

Quote:

Originally Posted by kavanaru

it depends onhow "clean" your two albas are... but if you keep crossing albas for several generation, you will get to a point of 100% albas...

True, but I don't know how many years that would take!! The time for the plants to grow and bloom, then for the seed pods to grow.... repeated about 6 times to get rid of all the recombinants! I'd be an old granny by then!

Undergrounder · #5 11-09-2008, 09:52 AM

Ah just the helpful info i was looking for, thanks guys!

I think the two cultivars i have have probably been line bred for a while, i might have to check with the breeder. I just don't want to sell them as "var. alba" if there's a chance one of seedlings might revert to standard.

Brooke · #6 11-09-2008, 12:25 PM

Just remember, genes never disappear, they only get buried. Once a gene is introduced it can express itself when paired up with the same recessive gene from the other parent.

Brooke

Undergrounder · #7 11-09-2008, 12:56 PM

Quote:

Originally Posted by brooke

Just remember, genes never disappear, they only get buried. Once a gene is introduced it can express itself when paired up with the same recessive gene from the other parent.

Brooke

So i presume line breeding of the alba would reduce this possibility in successive generations? Not including interacting genes but Generally speaking? ie: A 5th generation line-bred alba cross would have mostly albas, but a few might be normal? .. and then in the 100th generation i would probably get 99% albas, (very sickly ones at that), but i could POSSIBLY get a freak normal due to the buried genes?

Brooke · #8 11-09-2008, 08:24 PM

As I said in my first post, I can't give you any percentages. If I were a betting person, I would say you could get a high percentage of albas.

Freak? No I wouldn't call them freaks if a normal bloom expressed itself but with some good luck, you could possibly get something even more unique. Who knows, might even drag out a coerulea gene in the breeding.

Phal. violacea 'Blue July 4th x 'Gaston Bleu'

Brooke

littlefrog · #9 11-09-2008, 09:26 PM

Albinistic traits are usually recessive, I am pretty sure. That gets into the biochemistry of the whole thing, most albas lack normal biosynthesis of color pigments, they don't produce a special 'white' pigment. Just one 'normal' allele of the gene (any heterozygote) should produce enough of the necessary enzyme to produce some pigment. So, the genotype of your parents should be homozygous recessive (aa, to use the terminology above). The problem is that there could be multiple genes (loci, the fancy word for that).

Anyway, what that boils down to is that if your genes are behaving in a classic mendelian fashion (they aren't physically linked together, and aren't inherited in the chloroplast or other plastid genome, and.. it gets complicated), and they share the same gene for the trait (aa x aa) then they should have 100% homozygous recessive offspring (aa). If they don't share the same gene then it looks something like this, with A and B being your loci -

aaBB x AAbb = AaBb

In that case, all your progeny will be heterozygous at both loci, and probably colored. Now you could get a double homozygous recessive in the next generation. AaBb x AaBb = 9:3:3:1 (that 1/16 is your double recessive). I'm not drawing out the squares for you. But I'll probably make my students do it on Thursday, that is a good problem for their genetics test.

With some judicious line breeding and back crossing you could get to some pure breeding albas in a few generations. Of course that is maybe 10 years of real time, but what else were you going to do? If you are working with a single locus you would know it within one generation.

Don Perusse · #10 11-10-2008, 09:02 PM

WOW! That was pretty heady stuff!