Linkage relationships as a useful tool to state interspecific gene homology: Case study with isozyme loci in Austrocedrus chilensis (Cupressaceae)

Abstract

Linkage relationships among 12 polymorphic isozyme loci were analyzed in Austrocedrus chilensis (D. Don) Florin et Boutelje. Double or multiple heterozygous individuals were chosen from a general genetic inventory of 403 trees. Twenty-nine out of 66 possible pair-wise combinations were found. Between 21 to 187 macrogametophytes per tree were subjected to horizontal starch gel electrophoresis. Linkage was proved through individual and pooled data between four pairs of genes. Three of them showed a tight linkage: Aat2similar to6Pgdh2 (frequency of recombination R = 0.122 +/- 0.036), Aat3similar toSod (R = 0.125 +/- 0.021) and Aat1similar toPgi2 (R = 0.143 +/- 0.030), while a moderate linkage was found with respect to the pair Idh2similar toSkdh (R = 0.333 +/- 0.052). The inheritance of two allozyme gene loci was additionally proved: Aat2 and Pgi2, each locus with at least two alleles. Thus, two new isozyme markers are reported for this species. Different considerations for the establishment of a correct homology of gene loci before doing interspecific comparisons are discussed. The relative migration distance of isozymes on zymograms is proven as non sufficient evidence of homology of the encoding genes between species. On the other hand, linkages are shown to be a good tool for this purpose due to the highly conservative arrangement of the genes among related species.