The genetic basis of enzymatic variation was investigated in Salix exi
gua Nutt., a widespread North American willow species. Biochemical var
iation of 26 enzyme systems in the parental clones and full-sib famili
es of a 2 x 2 balanced factorial design was assayed, employing starch
gel electrophoresis. Results suggested that 14 enzymes are encoded by
multilocus systems, while 12 enzymes are under single gene control. A
total of 51 structural genes were revealed. Genetic determinism studie
s verified disomic inheritance, Mendelian genetic control and codomina
nt allelic expression in 13 loci. In the other 38 cases putative loci
were assigned. Segregation distortion was detected in Pgi-2 and Ppo-1.
In general, Salix exigua seems to be functionally diploidized.