Stacking S5-n and f5-n to overcome sterility in indica–japonica hybrid rice

Abstract

Pyramiding of S5 - n and f5 - n cumulatively improved seed-setting rate of indica-japonica hybrids, which provided an effective approach for utilization of inter-subspecific heterosis in rice breeding. Breeding for indica-japonica hybrid rice is an attractive approach to increase rice yield. However, hybrid sterility is a major obstacle in utilization of inter-subspecific heterosis. Wide-compatibility alleles can break the fertility barrier between indica and japonica subspecies, which have the potential to overcome inter-subspecific hybrid sterility. Here, we improved the compatibility of an elite indica restorer line 9311 to a broad spectrum of japonica varieties, by introducing two wide-compatibility alleles, S5-n and f5-n, regulating embryo-sac and pollen fertility, respectively. Through integrated backcross breeding, two near isogenic lines harboring either S5-n or f5-n and a pyramiding line carrying S5-n plus f5-n were obtained, with the recurrent parent genome recovery of 99.95, 99.49, and 99.44 %, respectively. The three lines showed normal fertility when crossed to typical indica testers. When testcrossed to five typical japonica varieties, these lines allowed significant increase of compatibility with constant agronomic performance. The introgressed S5-n could significantly improve 14.7-32.9 % embryo-sac fertility in indica-japonica hybrids. In addition, with the presence of f5-n fragment, S5-n would increase the spikelet fertility from 9.5 to 21.8 %. The introgressed f5-n fragment greatly improved anther dehiscence, embryo-sac and pollen fertility in indica-japonica hybrids, thus leading to improvement of spikelet fertility from 20.4 to 30.9 %. Moreover, the pyramiding line showed 33.6-46.7 % increase of spikelet fertility, suggesting cumulative effect of S5-n and f5-n fragment in seed-set improvement of inter-subspecific hybrids. Our results provided an effective approach for exploiting heterosis between indica and japonica subspecies, which had a profound implication in rice breeding.

Genomic Breeding of Green Super Rice Varieties and Their Deployment in Asia and Africa

“…The combination of various NILs with different blast resistance genes resulted in the development of varieties with consistent agronomic traits and high and stable resistance. In addition, the S5-n and/or f5-n from the wide compatibility variety Dular were introduced into the restorer line 9311, and the rapid detection of its background with RICE6K revealed a background recovery rate as high as 99.4%, resulting in the generation of improved 9311 with wide compatibility (Mi et al 2016).…”

Accelerated molecular breeding of a novel P/TGMS line with broad-spectrum resistance to rice blast and bacterial blight in two-line hybrid rice

“…Additionally, Pi2 was confirmed using two flanking markers, RM527 and HC28 in the MF4 (Jiang et al 2012 ; Jiang et al 2012 ). Polymerase chain reaction (PCR) for detection of the amplified products showing small SSR variations were performed as described in the previous study (Mi et al 2016 ). For the SNP variation, two photoperiod-sensitive genes pms3 and PMS1 , and one thermo-sensitive gene tms5 , were analyzed by Sanger sequencing based on site-specific genomic PCR, according to previous reports (Ding et al 2012 ; Fan et al 2016 ; Zhou et al 2014 ).…”

Development and evaluation of near-isogenic lines for brown planthopper resistance in rice cv. 9311

“…With development of next generation sequencing technology, large numbers of SNPs became available, and two breeding chips RICE6K and RiceSNP50 with high-throughput SNP arrays were developed in China3031, making efficient whole-genome background selection a reality. Background selection with high resolution SNP markers was used in rice breeding to improve blast resistance and wide compatibility1632. In the present study, the breeding chip RICE6K was employed in background selection for improving BPH resistance.…”