Hybrid necrosis as a barrier to gene transfer in hexaploid winter wheat × triticale crosses

Abstract

An interspecific wheat × 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 death of F1 hybrids from crosses between the most winterhardy wheat and triticale cultivars. This paper describes hybrid necrosis as the main barrier to gene transfer between winter wheat cultivars Borden, Augusta and Ruby, and hexaploid winter triticales OAC Wintri and K9-6. Crosses with tester lines revealed that the three winter wheats were carriers of the necrotic Ne2 allele. High temperature (30 °C) treatment until heading stage permitted to only partially circumvent the problem. A study of cross direction effects at the backcross level showed that the conventional method (F1 × wheat) was more efficient for plant recovery, but plants produced by the alternative backcross system (wheat × F1) were more self-fertile. Within the most winterhardy germplasm, 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 value as a bridge to circumvent the necrosis problem. Key words: Hybrid necrosis, Ne genes, wheat × triticale hybrids, cross direction