Inheritance of polymorphic isoenzymes in grape cultivars [Vitis vinifera]

The inheritance of nine polymorphic lsoenzyme systems encoded by 10 loci was studied in pollen of grape cultivars. The inheritance was inferred from the segregation in the F1 progenies of crosses made by hand pollination. The pattern of segregation of allozyme bands suggests that aliozymes belonging to the same enzyme system are controlled by single loci. An unusual phenotypic pattern was observed in two crosses for the enzymes peptldase-2 and tetrazolium oxldase, and two other crosses produced a segregation ratio for tetrazolium oxidase that did not conform to the one-locus Mendolian expecta tions. The latter cases may be interpreted as resulting from either a two-locus control or control by a gene duplication. The great amount of genic heterozygosity observed in grape cuitivars suggests that the majority of them, if not all of them, are single or multiple hybrids.