RESISTANCE TO BARLEY YELLOW-DWARF-VIRUS DISEASE IN DERIVATIVES OF CROSSES BETWEEN HEXAPLOID WHEAT AND SPECIES OF LOPHOPYRUM (TRITICEAE, POACEAE)

Among the wheatgrasses that are possible sources of genetic resistance for wheat to barley yellow-dwarf-virus disease (BYD) are those that h ave been commonly subsumed under the name Agropyron elongatum (Host) P . Beauv. Two of these wheatgrass species are the diploid Lophopyrum el ongatum (Host) A. Love (2n = 2x = 14) and the decaploid L. ponticum (P odp.) A. Love (2n = 10x = 70). These two species, the addition and sub stitution lines of L. elongatum chromosomes in hexaploid wheat (Tritic um aestivum L.), and derivatives of hybrids between hexaploid wheat an d L. ponticum, were screened for resistance to BYD, as defined by visu al symptoms in held-grown plants, The two species, an amphiploid deriv ed from L. elongatum x 'Chinese Spring' wheat, and the derivatives inv olving L. ponticum chromosomes were all highly resistant. The substitu tion and addition lines of L. elongatum chromosomes in 'Chinese Spring ' revealed that the genetic control of resistance in L. elongatum must be complex, with more than one critical locus involved. Chromosomes 2 E and 5E are involved and there are lesser contributions to resistance from the remaining wheatgrass chromosomes. One highly resistant deriv ative was determined to have only three pairs of L. ponticum chromosom es. It has a wheat-like morphology and shows promise for further chara cterization.