INTROGRESSION, TAGGING AND EXPRESSION OF A LEAF SENESCENCE GENE IN FESTULOLIUM

A mutation of a gene (discovered in Festuca pratensis Huds. and design ated sid) confers indefinite greenness on senescing leaves. Via interg eneric hybrids with Lolium multiflorum L. and Lolium perenne L., the m utant gene (sid(y)) has been introgressed into a range of Lolium backg rounds. Using genomic in situ hybridization we have identified segment s carrying sid(y) in recombinant chromosomes of Lolium-Festuca introgr ession lines. We also used L. perenne lines segregating 1:1 for the st aygreen character to tag the gene with molecular markers. In two mappi ng populations a total of 84 genotypes were screened with isoenzymes, RAPD primers, RFLP probes and AFLP primer pairs. Over 180 polymorphic loci were identified, representing 10 linkage groups spanning 600 cM. Two AFLP markers are linked to sid at 4.6 and 14.9 cM, close enough to be usable for marker-assisted selection. Introgression of sid(y) into Lolium temulentum L. resulted in the production of near-isogenic inbr eeding lines suitable for comparative studies of gene expression. Usin g a variation of the method of representational difference analysis a very small number of cDNAs have been identified as promising candidate s for sid, or genes directly regulated by sid.