Chromosome Numbers of Phrag. besseae and Phrag. dalessandroi

Say, I was thinking about the differences between Phrag. besseae and Phrag. dalessandroi. From the litterature Phrag. besseae has 24 chromosomes (and I have confirmed this myself from doing root squashes), while Phrag. dalessandroi has 28 chromosomes. Unfortunately we do not have any dalessandroi here at the nursery (that I know of), so my first question is has anyone else confirmed that dalessandroi indeed has a chromosome number of 28?

My second thought was (this is me as a Plant Breeder/Geneticist thinking). If it is true that besseae has 2n = 24 and dalessandroi has 2n = 28 chromosomes. This means that Phrag. Jersey has 2n = 26 chromosomes.

Number one this could be usefull to try to determine if an unknown plant is indeed Phrag. Jersey or one of the true species, but number 2 this means that this line of breeding (by crossing the 2 species with each other for multiple generations) will have a dead end. If you backcross Phrag. Jersey to either one of it's parents, say to Phrag. besseae the resulting hybrid will have 2n = 25 chromomosmes. If you cross it to Phrag. dalessandroi the resulting hybrid will have 2n = 27 chromosomes. Both Hybrids will have an uneven chromosome number. Usually plants that have an uneven chromosome number are sterile. Any thoughts about this, and does anyone know who has actually made these crosses?

Robert

Unfortunatly, getting people do do chromasome counts on plants isn't easy. You and Dean Stock are the only two people I know who do it.

I also thought I read that besseae flavum has a different chromosome count.

To bad you didn't post this last week, I could have given you some dalessandroi root tips to Jason for you to play with when I saw him this weekend.

Also, do you know if anyone has counted phrag andreettea?

Kyle

Yes, I should have thought about it last week....Well next time one of us goes to Canada, we should get some material. If you have a light microscope I can send you the protocol of how to count chromosomes from root tips, and than you can do it your self! It is pretty easy. The staining of the root tips only takes 1 day.

I don't know of anyone who has counted the chromosomes of andreettea.

Do you agree with me regarding that the 2nd generation hybrids (with uneven chromosome numbers) will probably be sterile?

Robert

Hell, I have Mem. Dick Clements x Jersey, I hope either the plants they were crossed w/ are 3N or you're wrong. Also, I only know 1 person here that has andreettae so that experiment will have to wait.

NYEric said:

Hell, I have Mem. Dick Clements x Jersey, I hope either the plants they were crossed w/ are 3N or you're wrong. Also, I only know 1 person here that has andreettae so that experiment will have to wait.

Click to expand...

Phrag. Jersey should be fertile, as it has 2n = 26 chromosomes, but what I was saying if you cross Phrag. Jersey back onto one of it's parents, either besseae or dalessandroi, that the next generation will be sterile, as the seedlings will have uneven numbered chomosomes.

Robert

Unless you cross it w/ ploidied parents!

You are correct, but I was talking about diploid plants. Phrag. species have a lot of different chromosome numbers from species to species, and I think this is why when you are doing Phrag breeding that you run into a lot of sterility problems. Usually first generation crosses will produce a lot of seed, but once you get into 3rd or 4th generation crosses your number of viable seedlings out of a cross will be greatly reduced. Like you said this can be overcome by using or creating tetraploids, but even then after so many generations you will run into sterility problems.

That is why Phalaenopsis breeding tends to be a lot easier, and you run into less sterility problems, as most Phal species have the same chromosome numbers.

Robert

Do you have a chart with the [natural] chromosome counts of the different species? Then we could actually figure out the odd/even count of the hybrids.

The numbers per Wimber are:

besseae: 2n= 24
besseae flavum: 2n= 24,25,26
dealessandroi: 2n= 28

I am not aware of any other countings....

add longifolium, schlimii and fischeri and you'll have 60+% of the hybrids!

I counted Phrag. besseae flavum myself, and I counted 2n = 24 chromosomes (same number as the red besseae). These are chromosome numbers of other species that I know of (I added ones that I did; me being Quene).

Phrag. besseae 2n = 24 (Wimber)
Phrag. besseae flavum 2n = 24 (Wimber, Quene) 2n = 25, 26 (Wimber)
Phrag boissierianum 2n =18 (Karasawa)
Phrag. caricinum 2n =21,22 (Karasawa)
Phrag. caudatum 2n = 28 (Karasawa)
Phrag. ecuadorense 2n = 22 (Karasawa)
Phrag. fischeri 2n = 30 (Quene)
Phrag. hartwegii 2n = 20 (Karasawa)
Phrag. kovachii 2n = 32 (Quene)
Phrag. lindenii 2n = 28 (Karasawa)
Phrag. lindleyanum 2n = 22 (Karasawa)
Phrag. longifolium 2n = 23 (Karasawa)
Phrag. longifolium var gracile 2n = 21 (Karasawa)
Phrag. pearcei 2n = 22 (Karasawa)
Phrag. roezlii 2n = 22 (Karasawa)
Phrag. sargentianum 2n = 22 (Karasawa)
Phrag. schlimii 2n = 30 (Karasawa)
Phrag. vittatum 2n = 18 (Karasawa)
Phrag. warscewiczianum (= popowii) 2n = 28 (Karasawa)

If you know of any other chromosome numbers please add them to the list.

Robert

Drorchid said:

Do you agree with me regarding that the 2nd generation hybrids (with uneven chromosome numbers) will probably be sterile?

Robert

Click to expand...

Hmmm. Actually, I don't think I do. It will still be diploid. The plant will have 25 pairs of chromosomes (each piece of pollen will have 1/2 of 25 chromosomes). Problems happen when you have 3 sets of chromosomes in a plant (3N). Then when you mate them there is some wierd division in miosis (spelling?) and each piece of pollen will have a wierd number of chromosomes.

EDIT: Upon thinking about it more, I guess it does have to have a even number for the 2N state. So I guess I would agree with you. So, is longifolium gracile (2N = 21) sterile as well?

The eric young foundation would probably have the most knowledge of breeding with Jersey.

Its my understanding that the non-consistant number of 2N chromosomes in phrag species, makes it hard to breed phrags 3-4 generations away from species or to include lots of different species in the mix.

Those are my thoughts and you know much more about these kinds of thing then I do. Maybe I'll send a link to this thread to Dean and see what his take on it is.

Kyle

Kyle said:

Hmmm. Actually, I don't think I do. It will still be diploid. The plant will have 25 pairs of chromosomes (each piece of pollen will have 25 chromosomes). Problems happen when you have 3 sets of chromosomes in a plant (3N). Then when you mate them there is some wierd division in miosis (spelling?) and each piece of pollen will have a wierd number of chromosomes.

The eric young foundation would probably have the most knowledge of breeding with Jersey.

Its my understanding that the non-consistant number of 2N chromosomes in phrag species, makes it hard to breed phrags 3-4 generations away from species or to include lots of different species in the mix.

Those are my thoughts and you know much more about these kinds of thing then I do. Maybe I'll send a link to this thread to Dean and see what his take on it is.

Kyle

Click to expand...

No, when you have 2n = 24 chromosomes, this means you have 12 pairs of chromosomes (n = 12), this means that if you have a pollen cell, it will have 12 chromosomes, and the ovule will also have 12 chromosomes.

If you have 2n = 25 chromosomes, this means during meiosis you will get an uneven split, as one of the chromosomes is not paired up, resulting in some pollen (or ovule) cells having 12 chromosomes and others having 13, usually an uneven split will result in sterility (not always). I looked up some chromosome numbers of other species, and they always have an even numbered chromosome number, that is why I was confused when I wrote down the numbers for longifolium being 2n = 21 or 2n = 23, which technically would mean they would be sterile.

Robert

Hi Robert,

I must have been typing my edit while you were typing your reply. I meant to type 1/2 of 25, not really thinking about what one half of 25 was. I see your point now...

I sent an email to Dean Stock, I bet he would have an answer.

Kyle

Drorchid said:

I counted Phrag. besseae flavum myself, and I counted 2n = 24 chromosomes (same number as the red besseae). These are chromosome numbers of other species that I know of (I added ones that I did; me being Quene).

Phrag. besseae 2n = 24 (Wimber)
Phrag. besseae flavum 2n = 24 (Wimber, Quene) 2n = 25, 26 (Wimber)
Phrag boissierianum 2n =18 (Karasawa)
Phrag. caricinum 2n =21,22 (Karasawa)
Phrag. caudatum 2n = 28 (Karasawa)
Phrag. ecuadorense 2n = 22 (Karasawa)
Phrag. fischeri 2n = 30 (Quene)
Phrag. hartwegii 2n = 20 (Karasawa)
Phrag. kovachii 2n = 32 (Quene)
Phrag. lindenii 2n = 28 (Karasawa)
Phrag. lindleyanum 2n = 22 (Karasawa)
Phrag. longifolium 2n = 23 (Karasawa)
Phrag. longifolium var gracile 2n = 21 (Karasawa)
Phrag. pearcei 2n = 22 (Karasawa)
Phrag. roezlii 2n = 22 (Karasawa)
Phrag. sargentianum 2n = 22 (Karasawa)
Phrag. schlimii 2n = 30 (Karasawa)
Phrag. vittatum 2n = 18 (Karasawa)
Phrag. warscewiczianum (= popowii) 2n = 28 (Karasawa)

If you know of any other chromosome numbers please add them to the list.

Robert

Click to expand...

phrag longifolium 2n= 20 (Atwood, Wimber) 2n=22,23 (Karasawa)

slippertalker said:

phrag longifolium 2n= 20 (Atwood, Wimber) 2n=22,23 (Karasawa)

Click to expand...

Thanks, 2n = 20 or 22 makes more sense than the other numbers that I had.

Robert

Insn't it kinda hit and miss when counting chromosomes? Sometimes they overlap or are hard to see, resulting in wierd counts, like three different numbers for besseae flavum.

Kyle

Kyle said:

Insn't it kinda hit and miss when counting chromosomes? Sometimes they overlap or are hard to see, resulting in wierd counts, like three different numbers for besseae flavum.

Kyle

Click to expand...

Yes, you are correct. Phrag chromosomes are kind of small, so when they overlap it is sometimes hard to count them. If I want to determine the chromosome number of a species, I have to look at multiple cells to get a good estimate of the chromosome number. I usually will count at least 5 to 6 root tips, and from each root tip try to find about 5 to 10 good cells, of which you can actually see all the individual chromosomes (sometimes I only can get 3 to 5 good cells in a whole root tip), count them and take an average for all the root tips. Sometimes when 2 chromosomes are next to each other (or overlap) it is hard to determine if they are actually 2 different chromosmes, or just 2 arms from the same chromosome.

What I use the chromosome counting more for is to determine the ploidy level. I don't have to be as accurate then as I just need a rough estimate of the number of chromosomes; also I don't have to count as many cells. For instance if it is a besseae, if I see about 22 to 26 chromosomes in a cell, I know it is a diploid, if I see about 46 to 50 chromosomes in a cell, I know it is a tetraploid. You can easily detect if there should be 24 chromsomes versus 48 chromosomes.

I think the fact that it is sometimes hard to count the chromosomes is why you see different numbers of chromosomes between the authors, and that probably also explains why some authors counted an odd number (while it should have been an even number).

Robert

Hey Robert,
Just a thought, my 2 cents. Keeping to the diploid crosses works fine for perpetuating the species. Once you get into hybrids - you are dealing with man-made ideals of beauty and generally the diploid is not the preferred product. You want polyploids, they sell better. Polyploids get awards. Polyploids have bigger flowers relative to plant size. As you run into the 2nd, 3rd and 4th generation sterility barriers in the diploids your seed yeild goes way down - BUT the few seedllings produced often are spontaneous polyploids or aneuploids that have dropped or doubled a chromosome or two to recover viability. What is best is breeding with these plants to see if you have the odd triploid, or tetraploid, or best yet the odd amphidiploid which will give you a plant with tetraploid characteristics that is super fertile like a diploid.
There are a dozen ways to end up with amphidiploids, but these types of chromosome counts give you the classic breeding clones. Look at Paph Winston Churchill, or BLC Oconee 'Mendenhall' all the best you want in tetraploid flower traits, but able to breed with anything, 2N, 3N or 4N. Super-breeders.

Of course it will take time in Phrags to test some of the better 3rd & 4th generation clones for their breeding traits. But I have seen a fair number of crosses coming out of Chuck Acker using Sunset Glow, Magdalena Rose, and other polyploid clones. He has been getting enough yeild to sell flasks, so Chuck has clones that have recovered fertility.

Fortunately the Phrags never get around to reading the reports of what their chromosome counts are - so they don't know they aren't supposed to breed. When you have a good plant with a superior flower - breed with it - if it produces seed, you win - from that you can guess at what configuration its chromosomes took.

Breeding orchids is not rocket science. Though Robert I know you are trying to be systematic so that you can guarrantee good yeild for your employer, your pay check depends on it. If by counting chromosomes you can predict yeild, that is to your benefit. But often we back into the scientific explainations after the fact, when the plant that wasn't supposed to breed, does breed. Look at Paph insigne 'Harefield Hall' it squashes out at 3N, but for some reason it produces a fair amount of seed with a significant portion (1/3 ?) of the offspring being tetraploid.

I for one won't give bench space to a 2N Phrag hybrid, I really like the look of the 3N and 4N Phrag hybrids. My assumption was that this was the direction most breeders were going. (I do keep a number of the species, and love them for what they are, in their glorious 2N forms)

Just my 2 cents. I used to try to do the chromosome counting thing, but found more often than not I was simply making myself crazy. Then I ran out of room for breeding.
Cheers
Leo