Self-incompatibility in Lolium species

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