Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 1997
Publication Date: N/A
Interpretive Summary: In order to make commercial forage sorghum hybrids, some system of cytoplasmic-male-sterility must be used (sorghum cannot be detasseled like corn). Nearly all commercial sorghum hybrids are made on lines male-sterilized with A1 cytoplasm. However, not all potential seed parent lines can be male sterilized in A1 cytoplasm. Alternate male-sterile ecytoplasms have recently become available and increase possibilities for hybrid testing and/or production. One alternate cytoplasm, A3, has very few know restorers of fertility. Hybrids made on A3 cytoplasmic male-sterilized seed parents would be expected to be sterile if grown in isolation (away from) from other sources of sorghum pollen. This study evaluates sorghum x sudangrass hybrids in A1 and A3 cytoplasm. Cytoplasm did not effect days to bloom, height, forage yield, or forage quality of the hybrids. Seed set under selfing bags (fertility restoration) in A3 hybrids was observed, was higher than expected for some lines implying that an additional source of A3 fertility restoration may be present in the sudangrass pollinators used in this study.
Technical Abstract: Several sorghum lines male-sterilized in A3 cytoplasm have been available since the early 1990's. Currently, no information is available comparing the agronomic performance of A1 cytoplasm and A3 cytoplasm sorghum sudangrass hybrids. However, based on other sorghum research results, A3 sorghum sudangrass hybrids would be expected to be male-sterile. If grown in isolation, these hybrids would not set seed, possibly providing high quality forage. The objectives of this study were to compare the effects of A1 and A3 cytoplasm on the maturity, fertility, height, forage yield, and forage quality of sorghum sudangrass hybrids. In 1989, pollen from a bulk of eight sudangrass populations (NP22, NP23, NP25, NP28, NP29, NP30, NP31, and NP35) was used to pollinate four sorghum lines that had been male-sterilized in both A1 and A3 cytoplasm (A1Martin and A3Martin, A1Redbine 58 and A3Redbine 58, A1Wheatland and A3Wheatland, and A1KS24 and A3KS24). Hybrids were grown at the University of Nebraska Field Laboratory, Ithaca, NE (Sharpsburg silty clay loam; fine montmorillonitic, mesic Typic Agriudoll) in 1990 and 1991 in a split plot design with inbreds (females) treated as whole plots and cytoplasms treated as subplots. Observed differences among hybrids for days to 50% anthesis were expected due to known maturity differences in the inbreds used as females. Cytoplasm had no effect on days to 50% anthesis, height, forage yield, in vitro dry matter disappearance (IVDMD), or crude protein. Seed set under selfing bags (fertility restoration) in A3 hybrids was observed, with interaction among A3 cytoplasm sources and various lines crossed into these cytoplasm sources.