POTENTIAL OF TRISPECIES BRIDGE CROSSES AND RANDOM AMPLIFIED POLYMORPHIC DNA MARKERS FOR INTROGRESSION OF MEDICAGO-DAGHESTANICA AND M-PIRONAE GERMPLASM INTO ALFALFA (M-SATIVA)

This report describes the production and cytology of the first intersp ecific hybrids between cultivated alfalfa (Medicago sativa L.) at the diploid level (2n = 2x = 16) and the diploid (2n = 2x = 16) perennial species M. daghestanica and M. pironae. An ovule-embryo culture techni que was required to rescue hybrid embryos and all hybrids were diploid . Predominately bivalent chromosome pairing was observed at meiotic me taphase. All F1 hybrids were male and female sterile and no species ba ckcross progeny could be produced. We discovered that trispecies hybri ds could be efficiently recovered via crossing diploid F1 interspecifi c hybrids of M. sativa X M. rupestris with either M. daghestanica or M . pironae. Ovule-embryo culture was also required to recover these tri species hybrids with recovery efficiency of trispecies hybrids about 1 0 times greater than for bispecies hybrids. Most chromosomes paired as bivalents in the trispecies hybrids. Importantly, progeny can be reco vered from crossing the trispecies hybrids with M. sativa. Therefore, the M. sativa X M. rupestris hybrids provide a bridge cross to potenti al introgression of M. daghestanica or M. pironae germplasm. Analysis of randomly amplified polymorphic DNA (RAPD) markers in the trispecies hybrids indicates that RAPD markers offer considerable potential for assaying germplasm introgression following complex hybridizations of t he type reported here.