Genetic variation for growth, quality and persistency characteristics
was assessed in six breeding populations of perennial ryegrass. Respon
se to multitrait selection was predicted in each population using a se
lection index based on 10 traits. Predicted response was compared with
that observed after one generation of half-sib family selection based
on breeder's preference. There was generally good agreement between p
redicted and observed response and it was possible to use predictions
to identify populations with good potential to meet breeding objective
s. For two of the breeding populations, observed selection responses a
fter three generations of recurrent selection and in the progeny of su
rvivors from cut and grazed plots were used to estimate selection pres
sures on individual traits. It appears that greater selection pressure
s are imposed on heading date and summer regrowth under grazing compar
ed with cutting managements. The results illustrate the value of a mul
tivariate approach in predicting the progress of breeding programmes a
nd in identifying traits most affected by natural selection pressures.