IDENTIFICATION OF A MAIZE LINKAGE GROUP-RELATED TO APOMIXIS IN BRACHIARIA

A bulked segregant analysis using RFLPs and RAPDs was carried out to i dentify molecular markers co-segregating with apomixis in a Brachiaria F-1 population. The test population used was a cross between sexual B . ruziziensis R44 and the aposporous apomictic Brachiaria brizantha cv Marandu. The Brachiaria genome was systematically scanned using 61 cD NA and genomic maize clones detecting 65 loci located at 40 cM, on ave rage, one from each other in the maize genome. The finding of a clone that presented a polymorphic band co-segregating with apomixis (umc147 ) led to the identification of another marker within the same area (um c72). The clones belong to a duplicated linkage group that maps to the distal part of maize chromosome-1 long arm and chromosome-5 short arm . RAPD analysis using 184 primers from Operon sets yielded one more ma rker (OPC4) significantly linked to the trait mapping the same locus. OPC4 had been previously reported as a potential marker for apospory i n Pennisetum A map of the region was constructed using additional clon es that belong to the same maize linkage group. Since that was the onl y genomic region that presented an apomixis-linked polymorphism our ob servations support the existence of a single locus directing apospory in Brachiaria.