Genetic characterization of the partial restorer of fertility gene, <i>Rf8</i>, in T cytoplasm maize

Meyer, Julie
Journal Title
Journal ISSN
Volume Title
Source URI
Research Projects
Organizational Units
Journal Issue

Texas (T) cytoplasm maize (Zea mays L.) is a model system for studying cytoplasmic male sterility and fertility restoration. The mitochondrial gene responsible for male sterility is T-urf13. Fertility is restored to T cytoplasm maize by the combined action of two nuclear genes, Rf1 and Rf2a. Rf1 is associated with the accumulation of additional 1.6/0.6 kb T-urf13 transcripts while Rf2a is an aldehyde dehydrogenase and not involved in transcript accumulation. There are also partial restorers of fertility for T cytoplasm. Rf8 and Rf*, with the combined action of Rf2a, restore partial fertility and are associated with the accumulation of additional 1.42/0.42- and 1.4/0.4-kb T-urf13 transcripts, respectively. Rf8 was positioned on the long arm of chromosome 2 near white pollen (whp1) using a segregating backcross population. PCR markers were developed to map Rf8. Flanking PCR markers that span a physical distance of 4.56 Mb in the B73 maize genome sequence correspond to a genetic distance of 8.28 ± 3.25 cM. This region includes seven pentatricopeptide repeat genes. Partially male-fertile plants segregated for the presence or absence of the Rf8-associated transcripts, indicating that presence of the 1.42/0.42-kb transcript is not necessary for anther exertion. Fertility phenotypes decreased with successive generations of backcrossing to (N) W64A, where as re-introducing the (N) wx1-m8 background increased fertility. The day after planting to the first flowering was observed for partially fertile and mostly fertile plants. Mostly male-fertile plants flowered 2.7 to 3.4 days earlier than partially male-fertile plants. These results demonstrate the flanking region rf8 is located in and the possibility that male fertility is under the control of more than one nuclear locus.

cytoplasmic male sterility, fertility restoration, linkage, maize, pentatricopeptide repeat, RNA processing