Ca. Kimbeng et Et. Bingham, Population improvement in lucerne (Medicago sativa L.): genetic analyses in original and improved populations, AUST J EX A, 39(5), 1999, pp. 549-554
Most quantitative genetics analyses are limited to the first (mean) and sec
ond (variance) degree statistics and their derivatives. Analyses based on t
hird (skewness) and fourth (kurtosis) degree statistics can be useful espec
ially for detecting and characterising the nature of gene interactions. Thi
rd and fourth degree statistics were analysed and used to interpret differe
nces in forage yield among S-1 families of lucerne derived from double-cros
s populations that were synthesised before (OGDC) and after (AGDC) improvem
ent via inbreeding and selection. Higher levels of genetic load (deleteriou
s alleles) were revealed in the OGDC population compared with the improved
population. The analyses also revealed the importance of gene interaction f
or forage yield in lucerne. In the unselected OGDC population, interaction
between alleles in repulsion phase linkages was more important, whereas, in
the selected AGDC population, interaction between alleles linked in coupli
ng phase assumed greater importance. The above results suggest that inbreed
ing and selection in lucerne can accumulate favourable alleles over generat
ions of selection and result in population improvement. Skewness and kurtos
is are relatively easy to compute and interpret and should serve as valuabl
e tools in tetraploid quantitative genetics analyses.