Allozymes of phosphoglucoisomerase (PGI) in cultivars of barley (Hordeum vulgare L.)

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Abstract
SUMMARY: The 65 spring and 14 winter cultivars of barley on the 1981 U.K. National List were examined electrophoretically for allozyme variants of phosphoglucoisomerase (PGI). Two different banding patterns were observed, a ‘fast’ and a ‘slow’ migrating type. With the exception of six spring cultivars in which the ‘slow’ type was found, all the cultivars were classified as ‘fast’. F2 progeny of crosses between ‘fast’ and ‘slow’ plants were used to interpret the banding patterns as resulting from the dimeric isozymes of two alleles (allozymes) each producing a triple band pattern, the faster two bands of which were considered to be ‘secondary’ or artefact bands. With the notable exception of Dragon and its sister line RPB 1115–75 all of the other ‘slow’ cultivars and breeders' selections were found to have the ‘slow’ cultivar Midas in their breeding history. Midas was bred using material from three ‘fast’ cultivars and a γ-ray mutant strain, the irradiation which produced this strain being regarded as the likely cause of the ‘slow’ isozyme. Unlike all the other cultivars tested, Midas was found to be a mixture of genotypes comprising 73% ‘slow’ and 27% ‘fast’ plants, a ratio which was most probably due to founder effects caused by the breeders' selection programme. In the light of the present investigation and other reports it is concluded that it is not an uncommon occurrence to find plants with different electrophoretic banding patterns within inbred cultivars.This result has serious implications for cultivar registration as there is a possibility of selecting electrophoretically distinct plants from within existing registered cultivars. It is concluded therefore that the protection afforded to plant breeders under Plant Breeders' Rights schemes could be seriously threatened by the use of electrophoretic characters for cultivar registration except in some specific incidences where it may be possible to apply appropriate safeguards. The implications for plant breeders of the existence of isozymes of PGI, of possibly different efficiencies, within commercial cultivars of the genus Hordeum are also discussed.