Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/28/2006
Publication Date: 5/3/2007
Citation: Tang, H.V., Pedersen, J.F., Chase, C.D., Pring, D.R. 2007. Fertility restoration of the sorghum A3 male-sterile cytoplasm through a sporophytic mechanism derived from sudangrass. Crop Science. 47:943-950. Interpretive Summary: Efficient hybrid grain sorghum production in the U.S. is dependent on the use of cytoplasmic male sterility (CMS), a trait that renders sorghum lines male-sterile. Male-sterile plants are pollinated with normal sorghum, and the resultant hybrid seed is sold to the farmer. Currently one source of CMS is used for essentially all grain sorghum production. Alternative sources of CMS must be compatible with seed production practices and be efficiently restored to fertility in the field. The IS1112C source of CMS has been shown to require two genes for fertility restoration. ARS scientists in Nebraska observed that certain sudangrass populations could confer fertility restoration. We recovered and characterized these lines and observed that the fertility restoration mechanism was different from that previously described, identifying an alternative means to restore fertility to this potentially useful source of CMS. These observations should be of interest to geneticists and plant breeders concerned with sorghum breeding and seed production.
Technical Abstract: Fertility restoration of sorghum lines carrying the IS1112C (A3 group) sorghum male-sterile cytoplasm in the line A3Tx398 has been documented as a two-gene gametophytic mechanism involving complementary action of restoring alleles designated Rf3 and Rf4, as derived from IS1112C. Fertility restoration capability has also been reported from sudangrass populations. We describe characteristics of a fertility restoration system derived from sudangrass. In this system, male-sterile individuals were observed at high frequency in backcross and F2/segregating populations. Segregation analyses of the derived restoration were generally consistent with a sporophytic restoration system involving two complementary genes. Pollen iodine stainability of certain of the progeny, however, was characteristic of gametophytic restoration. Possible silencing of restoring alleles through paramutation may be operative in these examples. Sudangrass-derived fertility restoration did not involve enhanced transcript processing of the chimeric mitochondrial open reading frame orf107. Thus male sterility induced by the A3 cytoplasm can be restored through different mechanisms.