Genetic Diversity of Synthetic Alfalfa Generations and Cultivars Using Tetrasomic Inherited Allozyme Markers

Enzyme electrophoresis was used to measure genetic variation within, and divergence
among, three generations of recently bred synthetic alfalfa generations (Syn1, Syn2, and
Syn3) originating from a polycross of 12 selected parents and several cultivars. Three
isozyme loci, exhibiting tetrasomic inheritance in 10-day seedlings, were detected from five
enzymatic systems analyzed by polyacrylamide slab gel electrophoresis for about 100
individuals of each alfalfa population. Very high levels of heterozygosity (ranging from
0.521 to 0.699) were observed within alfalfa populations, using polymorphic loci. The
reduction in heterozygosity was about 5% from Syn1 to Syn2 and from Syn2 to Syn3. The
last open pollinated generation was found to be in W-H equilibrium as well as Gharayonja,
a native ecotype under examination, using c2-test. Application of Wright's Fstatistics
revealed that the estimated overall inbreeding coefficient, (FIT), of 9.4% was
mainly related to inbreeding or double reduction in alfalfa (FIS= 8.61%) rather than
random genetic drift or population differentiation (FST= 1.6%). Therefore, due to very
large intra-population diversity, the breeding program of the synthetic alfalfa did not
generate a large variety differentiation. However, the use of seedling allozymic loci can be
applied successfully for estimation of the population genetic parameters.