THE GENETICS OF SOME ISOZYME VARIANTS IN TETRAPLOID WHEATS (TRITICUM TURGIDUM L.)

Progeny arrays obtained from crosses involving tetraploid wheat landrace genotypes which differed in their isozyme phenotypes, were assayed for the enzyme systems: Aconitate hydratase (Aco), esterase (Est), and cathodal peroxidase (Prx). The observed segregations fitted the expectations for monogenic Mendelian segregations in most of the cases, and the chi-square goodness of fit tests confirmed that the isozyme phenotypes in all the activity zones of aconitase, esterase, and in one zone of peroxidase, are controlled by different loci with codominant alleles. Concerning the phenotypes in the other two zones of peroxidase, evidence for monogenic segregation with dominance was found. Generally, the different regions of activity in each enzyme correspond to separate loci, which showed the presence of two aconitase, three esterase, and three peroxidase loci in the parental landrace genotypes. Joint segregation tests revealed that five locus pairs are linked and the extent of linkage between two pairs is tight while that between the remaining ones is moderate to loose. The distribution of these loci in the different chromosomes makes them potentially useful genetic markers in tetraploid wheats. Zygotic stage selection was believed to be responsible for the aberrant segregations observed.