From Discovery of High Lysine Barley Endosperm Mutants in the 1960-70s to New Holistic Spectral Models of the Phenome and of Pleiotropy in 2008

As documented by eight IAEA/FAO symposia (1968-82) on nutritionally improved seeds, a wide range of high lysine endosperm mutants were isolated in maize, sorghum and barley. These mutants observed by new spectroscopic screening methods can now be exploited to advance basic biological research and theory. Since 1982, effective methods to overview the physiochemical composition of seeds by Near Infrared Spectroscopy evaluated by chemometric data analysis have developed. Spectroscopic analyses by calibration have now substituted the wet analyses in the industry. In genetics there has traditionally been a differentiation between major genes for qualitative and minor 'polygenes' for quantitative traits. This view has been coupled with an incomplete understanding of pleiotropy. It is shown that seed spectra from isogenic barley endosperm mutants represent a coarse-grained physiochemical overview of the phenome that can be classified by chemometrics. Pleiotropy expressed by a gene is quantified as a whole pattern by the gene specific mutant spectrum subtracted by the spectrum of the parent variety. Selection for an improved plumpness (starch) in a breeding material with the lys3.a mutant visualizes in spectra the effect of enriching 'minor polygenes' for an increased content of starch in a mutant gene background. Morphological, spectroscopic and chemical analyses suggest that mutant genes have both qualitative and quantitative expressions. They produce qualitative pleiotropic phenomenological patterns that can be observed as more or less severe changes in macro and microstructures of the plant and seed phenotype. Behind are quantitative chemical changes that by spectroscopy and chemometrics can be transferred to qualitative patterns. In fact, one major gene for a qualitative trait can act as several apparent minor polygenes for quantitative variables. This explains the reduced need for the previously expected several hundred thousands of genes and gene modifiers down to the about 30,000 genes that are now sequenced in barley. (author)