Genetic Analysis of the Species Cytoplasm Specific Gene (scs[superscript d]) Derived from Durum Wheat

The action of species cytoplasm specific (scs) gene(s) can be observed when a durum (Triticum turgidum L.) nucleus is placed in the Aegilops longissimum S. & M. cytoplasm. This alloplasmic combination, (lo) durum, results in nonviable progeny. A scs gene derived from T. timopheevii Zhuk. (scs[superscript ti]) produced compatibility with the (lo) cytoplasm. The resulting hemizygous (lo) scs[superscript ti]- durum line was male sterile and when crossed to normal durum produced a 1:1 ratio of plump, viable (PV) seeds with scs[superscript ti] and shriveled inviable (SIV) seeds without scs[superscript ti]. In a systematic characterization of durum lines an unusual line was identified that when crossed to (lo) scs[superscript ti]- produced all PV seeds. When planted these PV seeds segregated at a 1:1 ratio of normal vigor plants (NVPs) and low vigor plants (LVPs). The LVP senescence before full maturity. The NVPs were male sterile and when crossed to common durum lines resulted in all plump seeds that again segregated at a 1:1 ratio of NVPs to LVPs. The crosses of these NVPs to common durum lines resulted in a 1:1 ratio of PV to SIV seeds. This study was extended to 317 individuals segregating for scs[superscript ti] and the new locus, derived from durum wheat (scs[superscript d]), establishing the allelic relationship of these two genes.