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 resto ration 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 hav ing 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.