Fine mapping of S37, a locus responsible for pollen and embryo sac sterility in hybrids between Oryza sativa L. and O. glaberrima Steud

Abstract

Hybrid sterility locus S37 between Oryza glaberrima and Oryza sativa results in both pollen and embryo sac sterility. Interspecific crossing between African cultivated rice Oryza glaberrima and Oryza sativa cultivars is hindered by hybrid sterility. To dissect the mechanism of interspecific hybrid sterility, we developed a near-isogenic line (NIL)-S37 using Dianjingyou1 (DJY1) as the recipient parent and an African cultivated rice variety as the donor parent. Empty pollen and embryo sac sterility were observed in F1 hybrids between DJY1 and NIL-S37. Cytological analyses showed that pollen abortion in the F1 hybrids occurred at the late binucleate stage due to a failure of starch accumulation in pollen grains. In addition, partial abortion of the embryo sac in the F1 hybrid was observed during function megaspore developing into mature embryo sac. Molecular analysis revealed that the semi-sterility was largely caused by the abortion of male and female gametophytes carrying the S37 allele from DJY1. A population of 25,600 plants derived from the hybrid DJY1/NIL-S37 was developed to fine map S37. Based on the physical location of molecular markers, S37 locus was finally delimited to a region of 205 kb on the short arm of chromosome 1 in terms of reference sequences of cv. Nipponbare. Interestingly, an about 97-kb DNA segment was deleted in the NIL-S37 based on BAC clone information of O. glaberrima. Fifty-four open reading frames (ORF) were predicted in this 205-kb region of DJY1, whereas only 31 ORFs were in that of NIL-S37. These results are valuable for cloning of S37 gene and further breaking reproductive isolation between Oryza glaberrima and Oryza sativa cultivars, as well as marker-assisted transferring of the corresponding neutral allele in rice breeding programs.

Lineage-specific gene acquisition or loss is involved in interspecific hybrid sterility in rice

“…To date, more than 10 loci for hybrid sterility between O. sativa and O. glaberrima have been reported (24)(25)(26). Among them, the HYBRID STERILITY 1 (S 1 ) locus on chromosome 6 has frequently been detected, suggesting that the S 1 locus is the major cause of the sterility barrier (11,13,14).…”

Anther culture in rice proportionally rescues microspores according to gametophytic gene effect and enhances genetic study of hybrid sterility

“…Eleven HS loci are currently known to be HS factors involved in pollen sterility in interspecific F 1 hybrids between O. sativa and O. glaberrima [ 6 – 15 ] (Table 1 ). Heterozygotes of gamete eliminator loci S 1 and S 37 (t) and pollen killer loci S 3 , S 19 , and S 20 preferentially transmit O. glaberrima alleles ( g ) to progenies, whereas heterozygotes of pollen killer locus S 21 transmit O. sativa alleles ( s ) [ 7 , 16 , 17 , 36 , 37 ].…”

Deployment of wild relatives for genetic improvement in rice (Oryza sativa)

“…(2015) developed NERICA lines for low land ecology derived from crossing O. glaberrima accessions viz., TOG5681, TOG5674 and TOG5675 with indica rice varieties IR64 and three elite breeding lines of O. sativa . Researchers have been utilizing this wild species for trait improvement and discovery of genes/QTLs through generating mapping populations for BB resistance (Gupta, 2010), BPH resistance (Ram, et al., ), green rice leafhopper (Fujita et al., 2010), rice stripe necrosis virus resistance (Gutiérrez et al., 2010), rice yellow mottle virus resistance (Pidon et al., 2017), resistance to root‐knot nematode (Galeng‐Lawilao et al., 2018; Lawilao et al., 2019; Petitot et al., 2017), drought tolerance (Wambugu et al., 2015), iron toxicity tolerance (Sikirou et al., 2016), salinity tolerance (Mondal, et al., 2018; Mondal, et al., 2018; Platten et al., 2013; Prodjinoto et al., 2018), flooding tolerance (Agbeleye et al., 2019) and sterility loci (Li et al., 2018; Shen et al., 2015). Recently a new gene for BB resistance xa45(t) (Neelam et al., 2020) and blast resistance Pi69(t) (Dong et al., 2020) has been mapped from an introgression line derived from O .…”