A total of thirteen F₁ ryegrass families, produced by crossing
genetically unrelated self -incompatible plants, were studied.
These included diploid and tetraploid F₁ families which displayed
a range of growth habits. The seven diploid F₁ families included
annual (L. rigid.um, Gaud.), biennial (L. multiflorum, L.), and
perennial species (L. perenne, L.). The six tetraploid F1
families included biennial and perennial species and, in addition,
the interspecific hybrid between L. perenne and. L. multiflorum.
Plants in each F1 family were crossed in a diallel array using
the petri dish technique and pollen tube penetration of stigmas
was observed by staining with aniline blue followed by fluorescence
microscopy. Differential pollen behaviour was observed on some
stigmas in all F1 families which indicated gametophytic determination
of pollen behaviour, Each F1 family displayed a complicated
pattern of compatible, incompatible and one way compatible
reactions and twelve P1 families had more than sixteen different
mating types. Thus, the self -incompatibility system appeared
to be controlled by more than two loci. In addition, three
levels of one ;ray compatibility were observed in some of the F₁
families. Plants which were reciprocally incompatible in both
diploid and tetraploid F₁ families frequently displayed different
mating types which indicated that not all the alleles in pollen
and pistil had to be matched to produce an incompatible reaction.
Pollen viability was estimated by staining pollen grains
with fluorescein diacetate and by culturing pollen grains
in vitro. While pollen from all F1 families tested could be
stained only pollen from non - annual Fi families was successfully
cultured in vitro. A low frequency of cytological abnormalities
which did not affect pollen viability, were observed in autoand
allotetraploid plants during pollen mother cell meiosis.