Genetic Effects on the Proportions of Conglutin γ and a Subunit of Conglutin β in the Storage Proteins of Lupinus angustifolius L. Seeds

Abstract

The genetic variability in the proportions of conglutin β and γ components of lupin seed storage proteins was explored in F₁, F₂ and F₃ families generated from a cross between two genotypes of Lupinus angustifolius cv. Uniharvest and a white-seeded selection from CPI 47644. The levels of conglutin γ differed by a factor of two in these parents, but varied continuously in the F₂ and F₃ families, indicating that the parental difference is due to several genes. These parents also differed in the level of a major conglutin β subunit, with a molecular weight of 30 000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the storage globulins from individual F₁, F₂ and F₃ seeds showed that the high level in cv. Uniharvest is controlled by an incompletely dominant allele, Bsc, at one locus, whereas the low level in CPI 47644 (white-seeded) is due to homozygosity for the recessive allele, bsc. The partial dominance of the Uniharvest gene suggests that the locus has a regulatory or processing function, so it has been designated beta subunit controller. F₃ families differed significantly in the level of the conglutin β subunit in Bsc/- seeds, indicating that other loci with smaller effects also influence the proportion of this subunit. The proportion of the β subunit in any seed depends largely on its own genotype, and not on the genotype of the maternal plant. The proportion of conglutin γ in the storage proteins varied inversely with the proportion of the β subunit. The implications of these results for the genetic improvement of the biological value of lupin protein are discussed.