Introgression of genes from Canada wildrye to slender wheatgrass: cytology and fertility of backcross progeny

Abstract

Partially fertile synthetic amphiploids (2n = 8x = 56) of Canada wildrye × slender wheatgrass F1 hybrid were crossed to slender wheatgrass and tetraploid lines resembling slender wheatgrass were recovered after four backcrosses. The BC1 progeny was hexaploid, while the BC2 and BC3 progenies were aneuploids with chromosome numbers ranging from 31 to 38. Tetraploid lines were recovered in the BC4 generation along with 29- and 30-chromosome types. Multivalents (mostly trivalents) resulting from intergenomic pairing were fequently encountered in BC1 and BC2 plants. The multivalent frequencies declined with each succeeding backcross. Pairing in the 28-chromosome BC4 plants was completely regular with 14 bivalents. Intergenomic pairing in the backcross progeny promoted introgression from Canada wildrye to slender wheatgrass.Key words: Elymus, intergenomic pairing, trivalents, recombination.