Claudio Jolowicz writes
Are apple and peach genetically related (and how)?

As I am not a biologist, I tried to simply google this. People say
apple, peach and quince are closely related, they show this result by
similarity tables, but no web site I found made any statements on the
genetical affinity of apple and peach.

Thanks in advance,

Claudio
=========
Stewart Robert Hinsley schreef
All three plants are classified in the same plant family - the Rose
family, Rosaceae. Whether this counts as closely related depends on what
one means by closely related. However they are not more closely related
to each other than each is to other plants within the family.

The Rosaceae is divided into subfamilies. The peach belongs to one
subfamily, Amygdaloideae. Within this family it belongs to the genus
Prunus - it being Prunus persica. The most closely related fruit to the
peach is the nectarine, which is a variety (i.e. within the same
species) of peach without the surface fuzz. I'd guess the most closely
related species is the apricot, Prunus armeniaca, but as there's several
hundred species of Prunus there's ample opportunity for me to be wrong
on this point.

The apple and quince belong to another subfamily, Maloideae. Apples
(there's many species) are classified in genus Malus. Quince is
classified in genus Cydonia, which is monospecific, quince being Cydonia
oblonga. There are many other genera in Maloideae, and it seems unlikely
that Cydonia is the most closely related genus to Malus. However, the
phylogeny of Maloideae appears to be confused; many intergeneric hybrids
occur, and genus boundaries are disputed. (I see that the taxonomists
have been chopping Sorbus into pieces.) The pears, genus Pyrus, are
often thought of as the more closely related genus to Malus. I'd guess
at Chamaemeles as the genus most closely related to Cydonia.

There are papers on the phylogeny of Maloideae out there, but the two
promising PDF files I found were restricted access, so I don't know
what's been said, beyond a few abstracts. There's also a pile of
sequences in GenBank/EMBL should anyone wish to draw their own tree.

Most of the subfamily Maloideae shares the same genomic structure, with
17 chromosomes in the haploid set. (A few basal genera differ). They are
descended from an ancient polyploid. (It's disputed whether it was an
amphiploid, or an aneuploid derivative of an autopolyploid.) The wide
range of intergeneric hybrids suggests little modification of the
structure of the chromosomes by duplications, deletions and inversions.
--
Stewart Robert Hinsley

+ + +
You are braver than I am.
I first took down Judd &al. and decided it was not safe to speak in general
terms about subfamilies in the Rosaceae, except Maloideae, which apparently
is a close natural unit.
PvR

PS: Really nitpicking, it is best not to mix Greek and Latin in one term, so
preferably it is either "monotypic" or "unispecific" ...