Abstract
Wild rice relatives having the same AA genome as domesticated rice (Oryza sativa) comprise the primary gene pool for rice genetic improvement. Among them, O. meridionalis and O. rufipogon are found in the northern part of Australia. Three Australian wild rice strains, Jpn1 (O. rufipogon), Jpn2, and W1297 (O. meridionalis), and one cultivated rice cultivar Taichung 65 (T65) were used in this study. A recurrent backcrossing strategy was adopted to produce chromosomal segment substitution lines (CSSLs) carrying chromosomal segments from wild relatives and used for trait evaluation and genetic analysis. The segregation of the DNA marker RM136 locus on chromosome 6 was found to be highly distorted, and a recessive lethal gene causing abortion at the seed developmental stage was shown to be located between two DNA markers, KGC6_10.09 and KGC6_22.19 on chromosome 6 of W1297. We name this gene as SEED DEVELOPMENT 1 (gene symbol: SDV1). O. sativa is thought to share the functional dominant allele Sdv1-s (s for sativa), and O. meridionalis is thought to share the recessive abortive allele sdv1-m (m for meridionalis). Though carrying the sdv1-m allele, the O. meridionalis accessions can self-fertilize and bear seeds. We speculate that the SDV1 gene may have been duplicated before the divergence between O. meridionalis and the other AA genome Oryza species, and that O. meridionalis has lost the function of the SDV1 gene and has kept the function of another putative gene named SDV2.
Highlights
Rice (Oryza sativa) is one of the most important staple crops in the world
For Jpn1, both BC3 F2 (Jpn1) and BC4 F2 (Jpn1) showed that normal gene segregation occurred around the HD1 locus (Figures 1 and 2). These results indicated that the two Australian O. meridionalis strains, W1297 and Jpn2, carry a recessive lethal gene causing abortion at the seed developmental stage, which was located between the two DNA markers, KGC6_10.09 and KGC6_22.19, spanning 12 Mb on chromosome 6, and that the Australian O. rufipogon strain Jpn1 does not carry such a gene
There have been many genes conferring hybrid seed sterility, hybrid pollen sterility, and segregation distortion found on Oryza chromosome 6 in inter-and intra-specific crosses, most of which O. sativa is involved with [21,22,23,24,25,26,27]
Summary
Rice (Oryza sativa) is one of the most important staple crops in the world. It feeds about one-third of the world population. Wild rice relatives having the same AA genome as domesticated rice comprise the primary gene pool for rice genetic improvement and include the following species; O. rufipogon, O. meridionalis, O. glumaepatula, O. barthii, O. longistaminata. Though there are several reproductive barriers among these species as described below, transfer of useful genes such as disease resistance gene from AA genome Oryza species to rice has been successful via hybridization.
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