9. Intra- and interspecific variability in grain protein distribution pattern in cultivated and wild species of Oryza

Department of Botany, University of Kerala, Kariavattom, Trivandrum-695 591, India

It is estimated that about 29% of the total protein content in rice grains is usually lost during milling and polishing due to the concentration of protein in the peripheral aleurone and sub-aleurone layers (Grist, 1959). A deep seated and diffused protein distribution pattern would be highly desirable for retaining the nutritive value of milled rice (Kaul et al., 1969). Though we have information on the intraspecific variability for this character involving mainly advanced cultivars of Oryza sativa and their induced mutants (Vilawan and Siddiq, 1973), there seems to have been no report on the situation among land races of O. sativa particularly from South India and accessions of wild species of Oryza. Earlier studies in this department involving land races collected mainly from the hill tracts of Kerala had revealed considerable intraspecific variability for this character (Nair, P.G., Nair, P.N.C. and Cyriac, K.J., unpublished). The present report deals with the variability for this character among some recent collections of O. sativa and accessions of six wild species of Oryza.

A total of 38 accessions including 9 land races and improved strains of O. sativa, 8 accessions of O. malampuzhaensis, 2 accessions of tetraploid O. punctata and 1 accession each of O. eichingeri, O. granulata and O. officinalis were studied using the protein specific bromophenol blue stained microscopic screening method standardized by Kaul et al. (1969). The preparations were scored and classified into 5 major types according to the procedure described by Vilawan and Siddiq (1973), as follows:

Type 1:-Big protein bodies, coalesced or closely arranged in the peripheral, subperipheral and outer layers of middle zones with medium sized and small bodies in the subperipheral, middle and central zones.

This idealmost protein profile with deep seated and diffused protein distribution was seen in the upland medicinal variety of O. sativa var. Navara and an improved strain Jyothi.

Type 2:-Big protein bodies less closely arranged in the peripheral and sub-peripheral regions and medium sized and small bodies more or less uniformly arranged in the subperipheral and middle zones and sparsely in the central zone.

Four accessions of O. sativa/rufipogan complex, the two accessions of O. punctata (Fig. 1C), one accession of O. eichingeri and O. officinalis (Fig. 1D) belong to this type.

Type 3:-Big protein bodies less closely arranged in the peripheral and subperipheral regions and medium sized or small protein bodies or very small protein granules distributed in the subperipheral and middle regions. The central region is devoid of protein bodies.

Type 4:-Big protein bodies less closely arranged in the peripheral and sub-peripheral regions and small protein bodies distributed in the sub-peripheral region. The middle and central region are devoid of protein bodies.

Six land races (Cherumodan, Kuruva, Black Chityani, Nayaruvithu, Kutticheradi, and Panamkurava), three improved cultivars (No. 20, H-4 and Ponmoni) and 3 accessions of O. sativa/rufipogon complex showed this pattern of protein distribution.

Type 5:-Big protein bodies very sparsely arranged in the peripheral and occasionally in the sub-peripheral regions.

Eight accessions of O. malampuzhaensis (Fig. 1F) and one accession of O. granulata had this type of protein profile.

Due to the small number of accessions represented in each group, an extensive analysis of intra and interspecific variations was not possible in the present study. However, the study has shown in corroboration with early reports that there is considerable intraspecific variation regarding grain protein distribution pattern among both land races and advanced cultivars of O. sativa. A traditional upland medicinal variety Navara (Fig. 1A) and an improved high yielding semidwarf popular variety Jyothi (Fig. 1B) were found to show the ideal protein distribution pattern. Earlier studies in this department (loc. cit) had identified a few primitive land races which possessed desirable deep seated and diffused protein distribution and Choramodan collected from Kodanad forest Range in Kerala state had, in addition, dwarf plant type, short duration and drought resistance.

Among the wild species, accessions of O. sativa/rufipogon complex showed considerable variation with Type 2, Type 3 and Type 4 protein profiles. O. malampuzhaensis, an endemic polymorphic species of S. India (Annie and Nair, 1990) showed the least intraspecific variation among the eight accessions screened, all having the most undesirable protein profile. One accession of O. granulata, another endemic wild species also showed the undesirable distribution similar to O. malampuzhaensis. The two accessions of tetraploid O. punctata (Fig. 1C) and one accession each of O. eichingeri and O. officinalis (Fig. ID) had good protein profile (Type 2).

The present study shows that there exists interspecific variability regarding this character among the wild species of Oryza. The present report also points to the necessity of undertaking an extensive screening of the land race rice germplasm of Kerala for characters like protein distribution pattern for future utilization in breeding programmes.

We thank Prof. Susan Abraham, Head, Botany Department, Kerala University for providing facilities. P. T. Annie acknowledges the associateship received under the UGC Departmental Special Assistance Programme.

Annie, P. T. and P. C. Nair, 1990. Polymorphism in Oryza malampuzhaensis. intern. Rice Res. Newsl. 15: 1.

Kaul, A. R., R. D. Dhar and M. S. Swaminathan, 1969. Microscopic screening of rice grains for protein characteristics. Curr. Sci. 38: 524-531.

Vilawan, S. and E. A. Siddiq, 1973. Study on mutational manipulation of protein characteristics in rice. Theor Appl Genet 43: 276-280.