Inheritance and linkage relationships of glutamate oxaloacetate transaminase isoenzymes in apple : 1. The gene GOT-1, a marker for the S incompatibility locus.

Four zones of enzymatic activity for glutamate oxaloacetate transaminase (GOT) were found in apple tissue. A dimeric gene, GOT-1, determining the fastest migrating zone, was identified. Six alleles were found, including a near null allelle which produced detectable heterodimeric bands but not homodimeric bands. A marked deficit or absence of certain geno-types in all backcrosses and in some crosses between unrelated varieties was attributed to the close linkage (r=0.02±0.005) of GOT-1 with the incompatibility S locus. GOT-1 was also closely linked with the isocitrate dehydrogenase locus IDH-1 (0.03±0.01). Proposed incompatibility genotypes for four cultivars, and the linked GOT-1 alleles are 'Cox': S 1 b/S 2 d, 'Idared': S 3 a/S 4 c, 'Fiesta': S 3 a/S 2 d and 'Kent': S 3 a/S 1 b.