The number of seeds and seed setting in the main spike were studied in primary octoploid triticale obtained from crosses between the common wheat cultivar Chinese Spring and 66 inbred rye lines. In some rye lines, the mutations of self-fertility were identified in the S, Z, or T incompatibility loci. The number of seeds was determined under controlled self-pollination of the main spike. In the set of triticale examined, each trait exhibited high variation. Hence, the rye lines were suggested to carry gene alleles both increasing and decreasing these traits in triticale. All the traits studied were significantly influenced by environmental conditions. Ten triticale lines were identified, which had the largest seed setting under self-pollination. Seven out of ten samples with the high number of seeds carried mutations in the T locus and in the three samples, the unidentified self-fertility mutations were present. The triticale lines with mutations in the S and Z loci displayed much lower self-fertility on average. The ways and means of identifying and mapping the rye gene responsible for distinctions between the triticale quantitative traits are discussed.