Fig 1.
Tassel fertility of CMS-C inbreds and F1 crosses.
(A) CMS-C line C-PH269ARf4Rf4 has sterile tassels. (B) F1 cross C-PH269A Rf4Rf4 x N-PH2FP0 Rf4Rf4 has fertile tassels. (C) CMS-C line C-PH2F3VRf4Rf4 has sterile tassels. (D) F1 cross C-PH2F3VRf4Rf4 x N-PH480C Rf4Rf4 has fertile tassels.
Fig 2.
Positional cloning recombinants and gene content within fine mapping interval.
(A) Region on chromosome 2 identified by whole genome QTL mapping which encompasses a PPR gene cluster containing known maize Rf genes. (B) The number of recombinants in each marker interval from the combined fine mapping populations. (C) PPRs located within the gene clusters. PPR names were collected from maizegdb.org as cataloged by Wei and Han 2016. The three candidate genes in the complementation test are indicated with hashed lines.
Table 1.
Degree of tassel fertility in C-PH269A BC1F1 mapping population.
χ2 test for Mendelian segregation of sterile to fertile (1:1). Scores of 1 and 2 are considered functionally sterile and 3 to 5 are considered functionally fertile.
Table 2.
F1 allelism crosses created with PH2F3V.
F1 crosses made with PH2F3V. Rf4 indicates restoring allele, and rf4 indicates non-restoring allele. Ppr153 indicates the presence of the PPR153 gene, and ppr153 indicates the absence of the PPR153 gene. One dose of each gene is required for tassel fertility.
Fig 3.
Complementation test demonstrates PPR153 is capable of restoring CMS-C in the presence of Rf4.
The plant on the left is hemizygous for PPR153 gene in the C-PH2F3VRf4Rf4 background and has restored fertility. The plant on the right is the null segregant within the C-PH2F3VRf4Rf4 population and is sterile.
Fig 4.
Anthers, pollen, and tassels from the PPR153 complementation test compared to Normal fertile cytoplasm.
(A) Anthers of the PPR153 null segregants are shriveled, whereas the PPR153 hemizygous anthers resemble Normal fertile cytoplasm anthers. (B) No pollen developed in the PPR153 nulls, as expected from unrestored CMS-C plants. The PPR153 hemizygous pollen and Normal cytoplasm pollen were full size and starch-filled when observed under a light microscope after 1% I2-KI solution staining. (C) PPR153 null segregants had no extruded anthers, whereas the PPR153 hemizygous and Normal fertile cytoplasm plants had extruded anthers.
Table 3.
Fertility score ratings of 7 PPR153 transgenic events.
The hemizygous plants were associated with restored fertility, and the null plants remained sterile.
Table 4.
Presence of PPR153 within NAM diversity lines.
For each NAM line, the presence of the PPR153 gene is indicated, and when present the gene name from MaizeGDB.org is listed. GDUSHD is growing degree day heat units to pollen shedding in Johnston, Iowa. Table is sorted by from early to late GDUSHD.
Table 5.
NAM population phenotyping to identify restoring ability linked to the chromosome 2 PPR cluster.
All plants contained restoring Rf4. NAM lines containing the PPR153 gene are indicated. Only the plants containing the chromosome 2 NAM haplotypes were phenotyped for tassel fertility scores. A score of 1 to 2 is considered functionally sterile, and a score of 3 to 5 is considered functionally fertile. The percent fertile plants associated with the NAM haplotype was calculated.