Search

The two-locus gametophytic incompatibility system in perennial ryegrass (Lolium perenne L.) is not always fully effective: obligate selfing of plants sieves self-compatible pollen mutants, and self-fertility becomes fixed in subsequent generations. Self-compatibility (SC) was investigated in an F2 family. In vitro self-pollinations were analysed and recorded and plants were classified as being either partially or fully compatible. Distorted segregation ratios of markers on linkage group (LG) 5 were found, which indicate the possible presence of a gametophytic SC locus. Interval linkage analysis of pollen compatibility after selfing confirmed that this distortion was due to a locus (T) analogous to the S5 locus of rye. However, even though markers in this region were, on average, less than 1?cM apart, the minimum number of plants possessing the unfavoured allele was never less than 6%for any marker locus. We proved that this was because of the presence of another SC locus, exhibiting gametophytic selection, segregating in this population and identified by interval mapping analysis of compatibility classes of in vitro self-pollinations. This locus was located on LG1, and probably corresponds to the S locus. We show that the T locus, a relic of a multilocus system, functions through interaction with the S locus: F2 segregation of incompatibility phenotypes and linked markers demonstrated that the S/t pollen genotype combination, expected to be compatible on selfing, was sometimes incompatible. Further evidence is presented to show that this interaction must be dependent on yet another locus located on LG2. A prime candidate would be the Z incompatibility locus.Heredity (2005) 94, 356-363. doi:10.1038/sj.hdy.6800582 Published online 29 September 2004 [ABSTRACT FROM AUTHOR]

Genomic in situ hybridization (GISH) on mitotic chromosome preparations of two diploid Lolium multiflorum-like drought-resistant plants derived from a L. multiflorum × Festuca arundinacea hybrid is described. With F. arundinacea DNA as probe, each introgression line was found to carry a single Festuca recombinant chromosome segment. In both plants, the introgressed Festuca chromosome segment was on the long arm of chromosome 2 of the L. multiflorum-like hybrid derivative. A DNA probe of E pratensis, which is one of the progenitor species of F. arundinacea, hybridized with the introgressed E arundinacea chromosome segment. It is likely that genes that confer drought resistance have been transferred from the F. pratensis subgenome of F. arundinacea to L. multiflorum. It follows that the F. pratensis chromosome in F. arundinacea which is homoeologous to chromosome 2 in L. multiflorum carries genes for drought resistance. [ABSTRACT FROM AUTHOR]