39. Isozyme diversity in some tetraploid wild species of rice

B.G. DE LOS REYES, D.S. BRAR and G.S. KHUSH

International Rice Research Institute, Manila, Philippines

The genus Oryza to which the cultivated rice belongs has 24 wild species. Of these, seven are tetraploids (2n = 48), namely O. punctata, O. minuta, O. latifolia, 

Table 1. Isozyme ploymorphism between O.sativa and 33 accessions of O.minuta
===============================================================================
                             Isozyme pattern
===============================================================================
Species Sdh-1 Pgi-1 Pgi-2 Amp-1 Amp-3 Amp-4 Pgd-1 Pgd-2 Got-1 Est-5 Mdh-1 Mdh-3

O.sativa   F    F     F     F     F     F    S      S      F    I     F     F
(IR31917-45-3-2)

O.minuta   S    F,S   F,S   F,S   F,S   F,S  F      F   F,I,S  F,S   F,S  F,S
===============================================================================
F=fast mobility;  S=slow mobility;  I=intermediate mobility


Table 2. Isozyme variation in 33 accessions of O. minuta
==============================================================================
Isozyme loci                                      Accessions
==============================================================================
Monomorphic
   Sdh-1, Pgi-2, Amp-2, Amp-3, Amp-4    100887,  101080, 101082, 101084,
   Adh-1, Pgd-1, Pgd-2, Got-3, Mdh-1,   101086,  101094, 101098, 101100,
   Mdh-2, Mdh-3, Est-5                  101101,  101128, 101129, 101133,
                                        101134,  101141, 101387, 103865,
                                        103874,  103875, 103876, 103877,
                                        103878,  103979, 103880, 103881,
                                        104674,  104676, 105123, 105124,
                                        105125,  105126, 105130, 105132,
                                        105253
Polymorphic
  Pgi-1        FF                       101128,  101129,  101387,  103874,
                                        103875,  103878,  103879,  103880,
                                        104674,  105123,  105126,  105130,
                                        105253
               SS                       101082,  101084,  101086,  101094,
                                        101100,  101133,  101134,  101141,
                                        103865,  103876,  103877,  103881,
                                        104676,  105125,   105121   
               FS                       100887,  101080,  101098,  101101,
                                        105124
  Amp-1        SS                       105123,   105153
               FF                         all accessions except two
                                          (105123,   105153)
  Got-1        SI                         all accessions except two (101134
               FS                          101134)
===============================================================================
FF= fast mobility;  SS=slow mobility;  FS, SI=heterozygous
O. alta, O. grandiglumis, O. ridleyi and O. longiglumis. Seeds of these species were obtained ftom the International Rice Germplasm Centre, IRRI. We analyzed isozyme diversity at 16 loci in 33 accessions of O. minuta, 6 of O. grandiglumis, 10 of O. punctata and 9 of O. alta using the procedure for starch gel electrophoresis described by Glaszmann et al. (1988).

The results on isozyme pattern of 33 accessions of O. minuta and O. sativa (IR31917-45-3-2) are given in Tables 1 and 2. Oryza minuta is distributed only in the Philippines. Of the 16 loci surveyed, O. sativa and O. minuta were polymorphic at 12 loci (Table 1). No polymorphism was observed between O. sativa and O. minuta for Anip-2, Adh-1, Got-3, and Mdh-2. As determined by the isozyme pattern, O. minuta accessions showed very narrow genetic diversity. All 33 accessions were monomorphic for 13 isozyme loci (Table 2). Only few accessions showed variation for three isozyme loci namely Pgi-1, Got-1, Amp-I (Table 2). On the other hand, O. grandiglumis from Brazil showed variation in several isozyme loci. Similarly extensive variation was observed in isozyme pattern amongst various accessions of O. punctata and O. alta.

The results on isozyme analysis indicate very low level of genetic diversity amonst 33 accessions of O. minuta and extensive variation in other three tetraploid species such as O. grandiglumis, O. punctata and O. alta. RFLP analysis of O. minuta accessions would be important to reveal genetic diversity.

References

Glaszmann, J.C., B.G. delos Reyes and G.S. Khush, 1988. Electrophoretic variation of isozymes in plumules of rice (O. sativa L.)-a key to the identification of 76 alleles of 24 loci. IRRI Research Paper Series, No. 134, 14 pp.