Shikimate Dehydrogenase-12 Allozyme as a Marker for High Seed Protein Content in Rice
1990
Shenoy, V. V. | Seshu, D. V. | Sachan, J. K. S.
Recent studies at the International Rice Research Institute (IRRI) on the N-assimilating isozymes in rice (Oryza sativa L.) showed that shikimate dehydrogenase high mobility allozyme (specified by the Sdh-1² allele) was associated with higher protein accumulation. This study was conducted to verify such association in FI and F₂ progenies derived from a cross involving parents differing in Sdh-1 alleles and seed protein content, and to examine the influence of the Sdh-1² allele on the Osborne's solubility fractions of total seed proteins. The female parent IR36 was characterized by the Sdh-11 allele and low seed protein content, and the male parent IR480-5-9-3-3, by the Sdh-1₂ allele and high seed protein content. The results indicated that the Sdli-1 locus assorted in a monogenic mendelian fashion expressing codominance, while the seed protein content segregated in a polygenic manner. When F₂ individuals were divided into three groups based on their Sdh-1 allozyme pattern as determined by starch gel electrophoresis of seeds and tillers, the mean protein content per seed was highest (120.3 g kg⁻¹ brown rice, BR) for Sdh-1² homozygotes, intermediate (106.0 g kg− BR) for Sdh-lˡ/Sdh-1² heterozygotes, and lowest (91.9 g kg-a BR) for Sdh-1¹ homozygotes. Accumulation of the oryzenin fraction in the heterozygotes and Sdh-1² homozygotes was significantly higher than in Sdh-P homozygotes. Since oryzenin is the major component of seed storage proteins in rice, the Sdh-1² allozyme can be an effective marker in screening for higher seed protein content among different cultivars or segregants from hybrid progenies. The study was supported partially by IARI-IRRI collaborative postgraduate training program.
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