INHERITANCE IN HEXAPLOID WHEAT OF LEAF RUST RESISTANCE AND OTHER CHARACTERS DERIVED FROM AEGILOPS SQUARROSA

Abstract

The inheritance of seedling leaf rust resistance and several morphological characters derived from Aegilops squarrosa (2n = 14 = DD) was investigated in a synthetic hexaploid wheat. The hexaploid was obtained by combining the tetraploid component (2n = 28 = AABB) extracted from the common wheat cultivar Canthatch with Ae. squarrosa var. meyeri R.L. 5289.A major, partially dominant gene was identified that gives good resistance (type 0;1 reaction) to leaf rust races 1, 5, 9, 11, 15, 30, 58 and 126a. This gene was shown to be different from the resistance genes Lr1, Lr2, Lr3, Lr10, Lr16, Lr17 and Lr18. A minor second gene was also detected which gives resistance (type 2 reaction) to race 9 and slight resistance to some of the other races.Each of the characters purple coleoptile, non-waxy foliage, brown glumes, and non-free threshing (tenacious glumes) of the synthetic wheat was monogenically inherited. The gene for threshability may be different from other genetic systems known to affect this character. The gene for brown glumes was linked with the major gene for leaf rust resistance with a recombination value of 3.1 ± 1.1%. The genes for non-waxy foliage and non-free threshing were associated with an estimated linkage value of 15.1 ± 2.6%.The results effectively demonstrated the relative ease with which genetic variation may be incorporated into common hexaploid wheat from its ancestral diploid, Ae. squarrosa, by means of a synthetic hexaploid intermediary. The method avoids the difficulties and complications often encountered with the transfer of genes from more distantly related species which do not have a genome in common with T. aestivum.