EVALUATION OF THE MALE-STERILE CYTOPLASM, MSM1, FOR USE IN HYBRID BARLEY SEED PRODUCTION (HORDEUM)

Possible maintainer lines were selected from CC XXXII and crossed onto cytoplasmically male-sterile plants. Complete male sterility was maintained in both the F₁ and BC₁ generations of 46.4% of the lines. Four cultivars with maintainer genotypes that were in both normal and msm1 cytoplasm were intercrossed using the male-sterile forms as the female parents. All F₁'s were completely male-sterile. Restoration of male fertility by 22 lines selected from CC XXXII was shown in each case to be due to a single dominant gene. In some lines, restoration was influenced by environment and genetic background. Partial restoration was observed in cultivars in the World Collection and lines selected from CC XXXII. Partial restoration appeared to be due to several genes that were subject to environmental influence. Accumulation of some of these genes increased the amount of restoration. There was no evidence that cytoplasmic factors were passed through the pollen. Twenty-two F₁ hybrids were produced by crossing restorer lines onto male-sterile msm1 lines. The 22 hybrids, their 44 parental restorer and maintainer lines and six check cultivars were grown in a four-replication yield trial. Total yield, 1000-seed weight and hectaliter weight were measured for each plot. All the F₁ hybrids outyielded their midparent values and 17 of the hybrids outyielded their high parents. Half of the F₁'s outyielded the high check cultivar, which yielded about 9,130 kg/ha. Twenty-one F₁'s had greater 1000-seed weights than their midparent values while only 11 F₁'s had greater 1000-seed weights than their high parents. The high check cultivar had the greatest 1000-seed weight, 49.0 gm. The hybrids with the greatest 1000-seed weights were not the hybrids with the greatest yields. Eighteen of the F₁'s had greater hectaliter weights than the midparent values, but only seven had greater hectaliter weights than their high parents. The high check cultivar had the greatest hectaliter weight, 75 kg. The hybrids with the greatest hectaliter weights were not the highest yielding hybrids