This document discusses allopolyploidy, which is when hybridization and genome duplication leads to plants with genomes from two or more species. Several important crop plants like wheat, cotton, and canola are allopolyploids. While some synthetic allopolyploids like triticale have emerged as new crop species, most are unstable and have defects that require extensive breeding to improve. Allopolyploidy can be used for creating new crop species or widening the genetic diversity of existing crops, but the effects are unpredictable and a vast majority fail to have agricultural value.

1. SUBMITTED TO:
Dr.Kaushik Kumar Panigrahi
Asst.Prof.in Plant Breeding and Genetics
SUBMITTED BY:
Chinmaya Sahoo
37HO/16
COLLEGE OF HORTICULTURE,CHIPLIMA

2.  Allopolyploids have genomes from two or
more species. Several of Our crop plants are
allopolyploids. Production of allopolyploids
has attracted considerable attention; the aim
almost always was the creation of new
species.

3.  Some success has been obtained as is evident
from the emergence of Triticale as a new crop
species in some areas, and the promise
shown by some other allopolyploids, e.g.
Raphanobrassica and some allopolyploids of
forage grasses.

4. species A
species B
X
Duplicated genomes are fertile !!
Botanical term: Allopolyploids
aborted gamete
production
Hybrid AB
body cells
Hybrid AB
during meiosis
spontaneous
genome
duplication
(fertile)
successful cell division
Hybrid AABB
“allopolyploid”
I. Allopolyploidy arises from hybridization plus
genome duplication

5.  .
II. Allopolyploids are special kinds of hybrids
species A
species B
X
.
III. Homologous pairing is predominant in
allopolplyoids
sterile fertileGenome
duplication

6.  .
homologous pairing homeologous pairing
IV. Homologous pairing is predominant in
allopolplyoids
V. Nomenclature for autopolyploids
Base number of chromosomes: X Humans: X=23
Gametic number: N Humans: N=23
Somatic number: 2N Humans: 2N=2X-46

7.  .
VI. Diploid vs. Allopolyploid hybridization
selfing generations genomes maintained separately

8.  .
What is the genomic composition of allopolyploid
hybrids of A. thaliana and A.. arenonsa ?
Comai et al., Chrom. Research, 2003
sample 1
sample 2
sample 3
Allopolyploid cells
FISH: fluorescent in situ hybridization
red: A. th centromeric repeat
green: A. are centromeric repeat
blue: chromosome arms (DAPI stained)
Pollen mother cells: early Anaphase I

9.  .
Black mustard
Chinese cabbage, Bok Choi
Cauliflower, broccoli, kale
QuickTime™ and a
TIFF (Uncompres sed) decompres sor
are needed to see this picture.
rape seed
Indian mustard
Collard greens
Brassica nigra
Brassica rapaBrassica olarecea
Brassica carinata Brassica juncea
Brassica napus
BB
AABB
AAAACC
BBCC
CC
picture sources: various www.
Allopolyploidy may lead to speciation
Example: Speciation in the cabbage family

10.  Allopolyploidy has three major applications in
crop improvement
 as bridging species in the transfer of character
from one species into another. In the production
of new crop species,
 for widening the genetic base of existing
allopolyploid crop species.

11.  The effects of allopolyploidy cannot be
predicted. The allopolyploids have some
features from both the parental species, but
these features may be the undesirable ones,
e.g. Raphanobrassica, or the desirable ones,
e.g., Triticale.

12.  Newly synthesized allopolyploids have many
defects, low fertility, cytogenetic and genetic
instability, other undesirable features, etc.
 The synthetic allopolyploids have to be
improved through extensive breeding at the
polyploid level. This involves considerable
time,labour and other resources.

13.  Only a small proportion of allopolyploids are
promising; a vast majority of them are
valueless for agricultural purposes (except for
their use as a bridging species). Thus a costly
trial and error has to be done before one is
likely to come across a promising
allopolyploid combination that can be
improved through breeding to yield a new
crop species.