In theory, it should be possible to do a cross between Phrags and Paphs.
The way to verify whether the progeny is truly a mix of these two genera is not by chromosome counts because Paph chromosomes would likely look just like Phrag chromosomes.
You would need to get DNA sequences that identify a given species, whether Paph or Phrag. So for a besseae x malipoense cross, you would first need to have some DNA sequences that are fingerprints for besseae as a species, and fingerprints for malipoense as a species.
The way to think of DNA is like a giant chain of letters billions of letters long. The letters are only A, C, G, T (the nucleotide components of DNA).
Here's a very short example. Imagine that the following sequence is a fragment of DNA from Phrag. besseae:
...ACTTCGACT
TGCTACGTTC
GACATTGCAG
CGTCCAGTGC
CTGCGTTCAG
T...
and this sequence is a fragment of DNA from Paph. malipoense:
...TTCGTCTTT
ACGTCTTTCG
AATCTAACTG
TTGTTTCCAA
CACTCGTCTT
C...
(Every tenth character is in bold)
What you'd be looking for is some set of short sequences that uniquely identify a given species. For example, for besseae, you might have on the above example a short segment between position 10 and 20 that is ONLY found in besseae. (i.e.,
ACGTCTTTCG
A)
Similarly, for malipoense, your research may determine that there is a short segment that is unique between position 35 and 45. (i.e., TCCAA
CACTCG)
Now, if you were to examine the plants from a putative besseae x malipoense cross, you would look for the presence of BOTH of the unique identifying sequences from the parent species.
If you find them both present, then you'll have demonstrated that the plant is indeed the result of a cross between besseae and malipoense (barring experimental error, of course).
In real life, it's not quite *this* simple, but this is the idea in general...
If you're interested in matters of orchid genetics, please check out my posts at
www.paphinessorchids.com.
DY Hung, Ph.D.