INHERITANCE IN HEXAPLOID WHEAT OF SEPTORIA-TRITICI BLOTCH RESISTANCE AND OTHER CHARACTERISTICS DERIVED FROM TRITICUM-TAUSCHII

In an attempt to find new sources of resistance to the disease septoria tritici blotch (STB) of wheat, we have evaluated a worldwide collection of the diploid species Triticum tauschii for their reaction to infection by pycindiospores of Mycosphaerella graminicola, the pathogen causing this disease. We have also screened a selection of synthetic hexaploid wheats, produced by hybridizing T. tauschii with tetraploid wheats, as well as the first and second generations of hybrids between some of these synthetics and commerical wheats. Almost 90% of the T. tauschii accessions and two-thirds of the synthetic hexaploids were resistant to STB. In the intercrosses with susceptible commerical wheats (e.g. Egret), the STB resistance was effectively transmitted as a single dominant gene, as indicated by a 3:1 ratio of resistant: susceptible plants in F2 progenies. In crosses with the STB-resistant wheat, M1696, a 15:1 ratio in F2 progenies indicated that the two resistance genes were different. F2 progenies involving the wheat cultivar Teal were more ambivalent. Other genetic traits also segregated in these plants although not all showed easily distinguishable phenotypic differences. Non-beneficial characters included genes for height, hybrid necrosis, grass clump dwarfism, tenacious glumes or threshability, speltoid head shape, and dark seed colour. Other genes controlled the more neutral characters coleoptile colour, hairy glumes and glume colour. Beneficial genes include resistance to septoria tritici blotch.