Differential Nucleo‐Cytoplasmic Interactions Involving Aegilops longissima Cytoplasm and Nuclei of Emmer and Common Wheat 1

Previous attempts to substitute euploid nuclei of Triticum durum Desf. and T. aestivum L. into the cytoplasm of Aegilops longissima S. & M. failed because one alien chromosome always remained fixed in the wheat nucleus. However, the alien chromosome was absent or the action of the gene(s) on this chromosome was modified in an exceptional progeny after eight backcrosses (BC 8 ) to T. durum which contained four exceptional 29‐chromosome male‐sterile plants with 14”+1’. In BC 9 and BC 10 generations, these plants produced a small number of viable seeds, and 29‐chromosome plants of material constitution were obtained. In this study, these plants were used as the cytoplasmic source to develop alloplasmic euploid T. aestivum with Ae. longissima cytoplasm. However, euploid T. durum with Ae. longissima cytoplasm was not obtained either from the use of these alloplasmic T. aestivum plants or from F 1 hybrids of 29‐chromosome plants ✕ euploid T. aestivum . Both sets of progenies from backcrosses with T. durum as the recurrent male parent, contained all 29‐chromosome plants, where the Ae. longissima chromosome was replaced by one D‐genome chromosome from T. aestivum . Like the Ae. longissima chromosome, this D‐genome was also maternally transmitted to all viable progeny. Thus, one chromosome of Ae. longissima or a D‐genome chromosome from T. aestivum was essential to have viable T. durum plants with Ae. longissima cytoplasm, even though euploid T. aestivum with Ae. longissima cytoplasm had normal fertility and plant vigor. These results show that euploid nuclei of T. durum and T. aestivum have differential interactions with the cytoplasm Ae. longissima . Therefore, Ae. longissima is cytoplasmically different from the emmer and common wheats, and Ae. longissima may not be the diploid B‐genome progenitor of emmer wheats.