Abstract
Various kinds of reproductive barriers have been reported in intraspecific and interspecific crosses between the AA genome Oryza species, to which Asian rice (O. sativa) and African rice (O. glaberrima) belong. A hybrid seed sterility phenomenon was found in the progeny of the cross between O. sativa and O. meridionalis, which is found in Northern Australia and Indonesia and has diverged from the other AA genome species. This phenomenon could be explained by an egg-killer model. Linkage analysis using DNA markers showed that the causal gene was located on the distal end of chromosome 1. Because no known egg-killer gene was located in that chromosomal region, this gene was named HYBRID SPIKELET STERILITY 57 (abbreviated form, S57). In heterozygotes, the eggs carrying the sativa allele are killed, causing semi-sterility. This killer system works incompletely: some eggs carrying the sativa allele survive and can be fertilized. The distribution of alleles in wild populations of O. meridionalis was discussed from the perspective of genetic differentiation of populations.
Highlights
IntroductionA hybrid seed sterility phenomenon was found in the progeny of the cross between O. sativa and O. meridionalis, which is found in Northern Australia and Indonesia and has diverged from the other AA genome species
Graduate School of Agriculture, Forestry and Fisheries, Kagoshima University, 1-21-24 Korimoto, Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Graduate School of Life Science, Tohoku University, Sendai 980-8577, Miyagi, Japan; Institute of Gene Research, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Kagoshima, Japan; Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Aomori, Japan; Abstract: Various kinds of reproductive barriers have been reported in intraspecific and interspecific crosses between the AA genome Oryza species, to which Asian rice (O. sativa) and African rice (O. glaberrima) belong
S5-i derived from indica and S5-j derived from japonica, S5-i and S5-j respectively act as killer allele and abortive allele, leading to semi-sterility, with about half of the seeds being sterile
Summary
A hybrid seed sterility phenomenon was found in the progeny of the cross between O. sativa and O. meridionalis, which is found in Northern Australia and Indonesia and has diverged from the other AA genome species This phenomenon could be explained by an egg-killer model. The interspecific crosses between O. sativa and the African rice O. glaberrima show hybrid vigor but are highly sterile both in pollen and seeds [14] Some causes of this hybrid sterility are explained by a gametic eliminator model [14,15,16]: In a heterozygous state of killer allele and abortive allele, both the eggs and pollen carrying the abortive allele are killed in the gametic eliminator model, causing semi-sterility in both spikelet and pollen. This divergence is reflected by the low pollen fertility of the hybrid between O. meridionalis and the other
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