Inheritance of isozyme variants in Austrocedrus chilensis (D. Don) Florin et Boutelje

Austrocedrus chilensis (D. DON) FLORIN et BOUTELJE, ''Cipres de la Cordillera'' is a dioecious conifer (Cupressaceae) that occupies a very wide precipitation range in the southern Andes Cordillera of South America. The drastic reduction of its natural distribution area in the last two centuries and its actual importance as a forest tree, make it essential to know the present range of its genetic variation in order to conserve and use it properly. To solve this through an allozymic approach the first step is to determine gene markers. Seeds of 368 trees from 15 populations mainly from the center of the natural distribution area, Megagametophytes (haploid tissue) from subjected to horizontal starch gel electrophoresis. Twenty enzyme systems were analyzed. Data from six polymorphic systems were tested for MENDELian segregation ratios resulting in 10 controlling loci codifying for 23 alleles. Thirty five percent of them are rare alleles with a frequency less than 0.01, determining minor polymorphism as the predominant genetic profile of this species for the analyzed loci. Phosphoglucomutase (PGM), leucine-amino peptidase (LAP) and glutamate dehydrogenase (GDH) reveal invariant electrophoretic patterns. In glutamate-oxalacetate transaminase (GOT) three zones were found; one invariant and the other two controlled by one locus each with three and two alleles respectively. Superoxide dismutase (SOD) showed a multiplebanded phenotype where one gene-locus controlling two alleles is postulated. Two zones revealed B- phosphogluconate dehydrogenase (6-PGDH), one of them controlled by one locus with three alleles. Five zones were found in malate dehydrogenase (MDH). Three of them showed variation with two, three and two alleles respectively. Isocitrate dehydrogenase (IDH) showed two zones, and both of them with two allelic variants. It was not possible to confirm statistically the variation observed in shikimate dehydrogenase (SDH). The importance of a planned sampling when determining gene markers is discussed.