HYB: Tetraploid Nomenclature
- To: Multiple recipients of list <i*@rt66.com>
- Subject: HYB: Tetraploid Nomenclature
- From: S* M* <7*@CompuServe.COM>
- Date: Fri, 28 Mar 1997 07:31:17 -0700 (MST)
Because the discussions have been getting more technical, I think the time has
come to acknowledge that we sometimes use the term "tetraploid" to keep an
explanation simple -- when a more precise term might apply. So here's a
mini-glossary that may be helpful:
The general term TETRAPLOID simply means it has four sets of chromosomes. It
tells us nothing about the types of chromosomes. It's the most appropriate term
for TBs, because after so many generations we just don't know which species
individual chromosome sets might have come from. In other cases, a more
precise term packs a lot of information in a little space.
An AUTOTETRAPLOID is a special type of tetraploid that has four sets of
chromosomes from the same species. Examples: a cultivar with only I.
stolonifera ancestry, or one with only I. pumila ancestry.
An ALLOTETRAPLOID has four sets of chromosomes, but at least one of them comes
from a different species. These are often infertile. Example: an ABBB-type
arilbred.
An AMPHIDIPLOID has four sets of chromosomes, two sets from each of two species.
These are usually fertile, but have breeding characteristics unlike either
diploids or autotetraploids. Example: a hybrid of I. stolonifera and I. pumila.
Any of these are often -- quite correctly -- called "tetraploids" for
simplicity's sake. But they have special meaning for hybridizers because some
tetraploids are fertile and others are not.
Sharon McAllister
73372.1745@compuserve.com
