Study of interrelationship among A-genome species of the genus Oryza through isoenzyme variation.

The interrelationships among ten different A-genome species of the genus Oryza were studied based on variations in the electrophoretic pattern of isoenzymes of two non-specific enzymes, esterase and peroxidase. There were 16 isoenzymes of esterase and 14 of peroxidase. The esterase pattern could be classified into 3 different Zymograms 1e, 2e & 3e based on the presence and/or absence of bands at particular Rf values. The pattern le was found exclusively among the species and varietal groups of sativa complex, whereas 2e and 3e were distributed exclusively among the species of the glaberrima complex and related wild forms. The peroxidase pattern also fell into 3 different zymograms viz. 1p, 2p and 3p. Unlike esterase, all three zymograms were present in both the sativa and glaberrima complexes.The similarity indices (S) between the different pairs of entries were computed taking into account the presence as well as the relative intensity of the corresponding isoenzyme bands. The varieties and sub-species of 0.sativa showed very high similarity values with the Asian perennis (O.perennis sub sp. balunga), lending evidence for the probable differentiation of the former from the latter. The African cultivated species O.glaberrima showed very high similarity to the African perennis form O.pevennis sub sp. barthii, O.breviligulata and O.stapfii. The only cubensis form studied had the same esterase and peroxidase pattern as that of the species of the glaberrima complex and also a very high similarity with this group. Thus, the entire A-genome species could be broadly grouped into the sativa and glaberrima complexes, and within the group there was a lot of overlapping in similarity values making it difficult to identify and pin-point species or subspecies based on their isoenzyme patterns and similarity values.