Submitted to: Helia
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/10/2003
Publication Date: 12/1/2003
Citation: Jan, C.C. 2003. Silencing of fertility restoration genes in sunflower. Helia. 26(39):1-6. Interpretive Summary: Sunflower hybrid production requires both stable male-sterile cytoplasm and fertility restoration genes. The restoration genes will restore the fertility in hybrids for seed production. New cytoplasmic male-sterile lines have been identified in wild sunflower PI 413178 and PI 413180, and corresponding fertility restoration lines have been developed. However, the effectiveness of the fertility restoration genes were adversely affected when crossed with certain cultivated sunflower lines. It is believed that those lines such as HA89, RHA266, and RHA274 possess gene(s) which suppress, or silence the expression of the restoration genes. Successful utilization of the new cms and fertility restoration lines depends on the effectiveness of selecting both lines free of the silencing genes. Restoration lines containing silencing genes can be identified and the silencing genes eliminated. Molecular marker development would assist in identifying cms lines without silencing genes.
Technical Abstract: Single dominant genes for fertility restoration of cytoplasmic male-sterile cmsANN2 have been identified in PI 413178, P21, and RCMG3, while PI 413180, P21, RHA801, RCMG1, and RHA280 were identified as restoration sources for cmsANN3. However, some cms plants were observed in progenies of homozygous restoration lines crossed with HA89, RHA266, and RHA274. It is believed that HA89, RHA266, and RHA274 possess gene(s) which suppress, or silence the expression of some Rf genes. HA821 does not have silencing gene(s), thus producing all male-fertile progenies after crossing with the restoration lines. F2 progenies of the half-diallel crosses among the three restoration lines for cmsANN2 and among the five restoration lines for cmsANN3 were nearly all male-fertile, suggesting a single Rf gene for each of the cms sources. However, testcross progeny families from crosses of half-diallel F1 with respective cmsANN2 and cmsANN3 were not all male-fertile, with most families having all male-sterile plants or segregating for both male-sterile and male-fertile plants. This could happen if cmsANN2(HA89) and cmsANN3(HA89) contain silencing gene(s) obtained from backcrossing with HA89. Restoration lines containing silencing genes can be identified and the silencing genes eliminated. Hidden silencing gene(s) in cms lines is a problem, and lines without these genes, such as HA821, should be used to develop maintainer lines. Gene silencing appears to be simply inherited. Molecular marker development would assist in identifying lines without silencing genes.