ABSENCE OF THE J-GENOME IN LEYMUS SPECIES (POACEAE, TRITICEAE) - EVIDENCE FROM DNA HYBRIDIZATION AND MEIOTIC PAIRING

To test the presence of a J genome in the type species of Leymus, L. a renarius, its total genomic DNA and that of tetraploids L. mollis, L. salinus ssp. salmonis, L. ambiguus, L. chinensis, L. secalinus, L. ala icus ssp. karataviensis, and L. innovatus were probed with the 277-bp insert of pLeUCD2, which can hybridize with the J, S, and P but not wi th the N, R, V, Q, I, T, and ABD genomes. The DNA probe hybridized wit h PalI- or TaqI-digested total DNAs from Thinopyrum elongatum (J(e)J(e ) diploid) and T. elongatum X Psathyrostachys juncea (J(e)N hybrid), b ut not with those from L. arenarius (NNNNXXXX octoploid) and all tetra ploid Leymus species (NNXX). Attempts to cross diploid Thinopyrum and tetraploid Leymus species yielded only one triploid hybrid, T. elongat um X L. salinus ssp. salmonis. Meiotic chromosome associations at meta phase I of pollen mother cells in the triploid hybrid averaged 19.69 u nivalents, 0.64 bivalents, and 0.01 trivalents per cell. Chromosome pa irings in the tetraploid hybrids of L. mollis X L. salinus ssp. salmon is, and the reciprocal cross, indicate that L. mollis and L. salinus s sp. salmonis shae the same genomic constitution. Both the DNA probe an d genome analysis results confirm the absence of the J genome in the s even additional Leymus species tested. Meiotic data indicated that tet raploid Leymus species could not have the genome formula N1N1N2N2; thu s their genome formulas should remain as NNXX until the source of X is identified.