HYBRID NECROSIS AS A BARRIER TO GENE-TRANSFER IN HEXAPLOID WINTER-WHEAT X TRITICALE CROSSES

An interspecific wheat x triticale hybridization program was initiated with the scope of widening and improving the winter wheat gene pool. However, progress was hampered by severe necrosis that caused the deat h of F-1 hybrids from crosses between the most winterhardy wheat and t riticale cultivars. This paper describes hybrid necrosis as the main b arrier to gene transfer between winter wheat cultivars Borden, Augusta and Ruby, and hexaploid winter triticales OAC Wintri and K9-6. Crosse s with tester lines revealed that the three winter wheats were carrier s of the necrotic Ne2 allele. High temperature (30 degrees C) treatmen t until heading stage permitted to only partially circumvent the probl em. A study of cross direction effects at the backcross level showed t hat the conventional method (F-1 x wheat) was more efficient for plant recovery, but plants produced by the alternative backcross system (wh eat x F-1) were more self-fertile. Within the most winterhardy germpla sm, hybrid necrosis is a major problem for transferring genes between winter wheat and triticale. The use of non-necrotic winter wheat lines such as MC11N, a local winter wheat selection, may have a special val ue as a bridge to circumvent the necrosis problem.