FERTILITY OF THE FIRST GENERATION HYBRIDS FROM CROSSES OF CYTOPLASMIC MALE STERILE BISON AND CHINESE SPRING ANEUPLOIDS

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Abstract
Male sterile winter wheat Bison in Triticum timopheevi cytoplasm (mst-BisonlO) was crossed with ''Chinese Spring (control crosses), and with ''Chinese Spring'' tetrasomics or trisomics and isosomics or telosomics. F1 hybrids were studied for chromosome number and pairing at metaphase 1 of meiosis in pollen mother cells, and for seed set in spikes on the main tillers. A marked variation in seed set among and within the F1 progenies occurred in the control crosses. In spite of this unexplained variation in seed set in control crosses, an addition or a deficiency of a chromosome or a chromosome arm influenced the amount of seed set on the F1 plants from crosses of mst-Bison1O with ''Chinese Spring'' aneuploids. In general, F1 trisomic-1B, -5B, -6B, or -6A, and those with 41 + iso-5B, iso-6B or telo-6A were partially fertile. The F1 plants with 41 + telo-1B (non-SAT arm), and monosomie-1B and -6A were sterile. A minimum dose of 2 of chromosomes 1B, 5B, 6B and 6A was necessary for partial male fertility restoration and an extra dose of 1B, 5B, 6B or 6A did not induce male sterility. A deviation from disomic condition involving any 1 of the 9 chromosomes, 1A, 3A, 5A, 2B, 1D, 2D, 3D, 4D, or 5D, resulted in complete male sterility or in a very low partial fertility. Chromosomes 2A, 4A, 4B, 7A, 7B, 6D and 7D in 1 extra dose inhibited male fertility, but depending on which arm of a particular chromosome was missing or duplicated, partial male fertility was restored in certain F1 plants with 41 + iso or telo of some of these 7 chromosomes.