6. Isozyme diversity in Oryza australiensis

B. G. de los REYES, D. S. MULTANI, D. S. BRAR and G. S. KHUSH

International Rice Research Institute, P.O. Box 933, Manila, Philippines

The wild species of rice are distributed in various geographical regions of the world. Oryza australiensis (2n=24 EE) is distributed in Australia. In O. australiensis the gene pool is limited to only a few accessions. The available 10 accessions of O. australiensis were analyzed. Very little morphological diversity exists in these accessions, hence we investigated isozyme variability.

The available 10 accessions O. australiensis were analyzed for 12 isozyme loci, Sdh-1, Pgi-1, Pgi-2, Amp-1, Amp-2, Amp-3, Amp-4, Adh-1, Pgd-1, Pgd-2, Got-1, Got-3, using starch gel electrophoresis. Of these 12 loci, 4 were monomorphic (Sdh-1, Pgd-2, Got-1, Got-3) and the other 8 showed polymorphism (Table 1). The allozyme pattern for 8 isozymes is given in Table 2. Considerable isozyme diversity was detected amongst various accessions. Each accession of O. australiensis showed unique allozymic combination for the 8 isozymes studied (Fig. 1). The results indicate that each accession of O. australiensis can be identified on the basis of isozyme profile.


Table 1. Isozyme polymorphism in O. australiensis
Enzyme                               Isozyme locus       No. of allozymes
Shikimate dehydrogenase              Sdh-1                         1
Phosphoglucose isomerase             Pgi-1                         2
                                     Pgi-2                         2
Aminonentidase                       Amp-1                         3
                                     Amp-2                         4
                                     Amp-3                         3
                                     Amp-4                         4
Alcohol dehydrogenase                Adh-1                        2
Phosphogluconate dehydrogenase       Pgd-1                         2
                                     Pgd-2                         1
Glutamate oxaloacetate transaminase  Got-1                         1
                                     Got-3                         1

Table 2. Allelic constitution for 8 isozyme loci among 10 O. australiensis
Acc.No.  Pgi-1  Pgi-2  Amp-1  Amp-2  Amp-3  Amp-4  Adh-1  Pgd-1*
100882    a      b      a      b      a      a      c      a
101397    a      b      a      b/d    b/c    b/d    c      a
101410    b      b      a      d      b/c    b/d    c      b
101144    a      b      b      c      a      b      c      b
103318    a      b      a      d      a      b      c      b
104090    a      a      c      a      a      b      c      b
105264    a      a      a      b      c      b/c    b      b
105269    a      a      a      b      b      b      a/c    b
105270    a      b      a      a/b    b      b      b/c    b
105272    a      a      a      b      b      b      c      b
* Mobility pattern a<b<c<d