| Additional cytoplasmic male sterility-fertility restoration
systems in Triticum1) S. S. MAAN and Karl LUCKEN Department of Agronomy, North Dakota State University, Fargo, U. S. A. Cytoplasmic male sterility in wheat has been obtained by substituting the Triticum nucleus into the tytoplasm of Aegilops caudata (KIHARA, 1951), Ae. ovata (FUKASAWA, 1953) and T. timopheevi (WILSON and Ross, 1962). Also, the T. durum nucleus substituted into T. timopheevi cytoplasm gives male sterile plants (present authors, unpublished). This paper reports two additional cytoplasmic male sterility-fertility restorer systems in Triticum. When the nucleus of the common wheat variety Justin was substituted into T. zhukovskyi cytoplasm, male sterile plants were produced. The T. durum uncleus substituted into a diploid wheat cytoplasm (2n=14, genome AA) produced male stetile 2n=28 chromosome plants. Fertility restoration factor (s) for these two sources of male sterility are believed to have been recovered during the substitution backcrossing. The diploid wheat used in these studies was a T. boeoticum-type of an unknown origin. One plant of this diploid was found in an F2 population from the cross mst-Selkirk2 x Chinese Spring mono-iso-7 D. This F2 population was grown from the seed set on a male fertile F1 plant with 20II + iso + 1I. This diploid plant and its progeny were morphologically distinguishable from T. monococcum and T. boeticum. This study was initiated to test the possible cytoplasmic effects of the T. durum nucleus substituted into the cytoplasm of this "derived diploid" and other diploid species of Triticum. A more detailed account of these investigations will be published elsewhere. Observations Chromosome Parring : T. zhukovskyi (2n=42) has the genome constitution of AAAAGG (BOWDEN, 1959). The metaphase-1 chromosome pairing in the PMC of the F1 hybrids of T. aestvum varieties " Justin " and " Chris" with T. zhukovskyi and the amphidiploid (T. timopheevi x Aegilops squarrosa)2, respectively, is given in Table 1. In the F1 hybrid (AAAGBD) with T. zhukovskyi an average of 9.4 univalents per PMC was observed, and the remaining chromosome formed bivalents and other complex associations including 1-2III and 1-2IV per cell. The F1 hybrid (AABGDD) from the cross with the amphidiploid had an average of 4.9 univalents, and a few PMC with no univalent chromosomes were observed. Also in this hybrid 1-2III and 1IV per PMC were common. The F1 hybrid (AAABBGD) from a cross between an amphidiploid (T. timopheevi x T. durum)2 and T. aestivum variety "Justin" had an average of 5.6 univalents and several trivalents per cell. Therefore, in these hybrids the majority of the B, G and D genome chromosomes were paired or otherwise associated with other chromosomes in most of the PMC. The chromosome pairing in the F1 hybrids from crosses of the T. boeoticum-type with T. durum, T. aestivum and T. monococcum, etc., is given in Table 1. The T. zhukovshyi, T. timopheevi, and the amphidiploids (T. timopheevi x Ae. squarrosa)2 and (T. timopheevi x T. durum)2 used in this study were obtained from Dr. B. C. JENKINS, Department of Plant Science, University of Manitoba, Winnipeg, Canada. |
| 1) Published with the approval of the Director, North Dakota Agricultural Experiment Station as Journal Article No. 87. |
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