New Hybrid Spikelet Sterility Gene Found in Interspecific Cross between Oryza sativa and O. meridionalis

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.

Seed abortion caused by the combination of two duplicate genes in the progeny from the cross between <i>Oryza sativa</i> and <i>Oryza meridionalis</i>

“…Oryza meridionalis is a wild rice with an AA genome native to Australia, offering a unique evolutionary path compared to other AA genome species (Brozynska et al 2017, Cheng et al 2002, Stein et al 2018, Zhang et al 2014. Reproductive barriers have been reported in a number of crosses between O. meridionalis and other AA genomic species (Banaticla-Hilario et al 2013, Ichitani et al 2022, Juliano et al 2005, Li et al 2018, Naredo et al 1997. In our previous study, we observed that no homozygote of O. meridionalis alleles for the loci closely linked with HD1 on chromosome 6 appeared in progenies from crosses between O. meridionalis and O. sativa (Toyomoto et al 2019).…”