Analysis of glutamate oxaloacetate transaminase (GOT) isozyme variants in diploid tuberous Solanum; inheritance and linkage relationships to ds1 (desynapsis), y (tuber flesh colour), cr (crumpled) and yc (yellow cotyledon)

Abstract

Employing polyacrylamide gradient-gel electrophoresis, the genetic control of leaf glutamate oxaloacetate transaminase (GOT) isozyme variants and their linkage to ds1 (desynapsis), y (tuber flesh colour), cr (crumpled) and yc (yellow cotyledon) were studied in diploid tuberous Solanum species hybrids. Leaf GOT isozymes proved to be dimeric and under the control of two independently segregating loci (Got-1 and Got-2) with two (1 s , 1 f ) and three (2 s , 2 f , 2 n )alleles respectively. The 2 n allele was concluded to encode a 2 fallozyme subunit capable of forming heterodimeric but no homodimeric active molecules. As expected with Got-1 and Got-2 isozymes being localized in different cellular compartments, no intergenic heterodimer formation was observed. In contrast to earlier studies, a gradual rather than discrete transition between the tuber flesh colour classes white and yellow was observed in segregating progenies. Adopting a standardized classification method, however, monogenic recessive inheritance of white tuber flesh was confirmed. Got-1, ds1 and cr were found to represent a single linkage group. Among the presently studied marker loci no further linkages were detected. As to linkage analysis, the difficulties imposed by gametophytic incompatibility in nearly all diploid potato species and by the frequent occurrence of recessive (sub)lethal genes are discussed.