A minimal genome design to maximally guarantee fertile inter-subspecific hybrid rice.

Hybrid rice has made considerable contributions to achieve the ambitious goal of food security for the world's population. Hybrid rice from indica/xian and japonica/geng subspecies shows much higher heterosis and is thereby an important innovation in promoting rice production in the next decade. However, such inter-subspecific hybrid rice has long suffered from serious hybrid sterility, which is a major challenge that needs to be addressed.

Identification of QTNs, QTN-by-environment interactions, and their candidate genes for grain size traits in main crop and ratoon rice.

Although grain size is an important quantitative trait affecting rice yield and quality, there are few studies on gene-by-environment interactions (GEIs) in genome-wide association studies, especially, in main crop (MC) and ratoon rice (RR). To address these issues, the phenotypes for grain width (GW), grain length (GL), and thousand grain weight (TGW) of 159 accessions of MC and RR in two environments were used to associate with 2,017,495 SNPs for detecting quantitative trait nucleotides (QTNs) and QTN-by-environment interactions (QEIs) using 3VmrMLM. As a result, 64, 71, 67, 72, 63, and 56 QTNs, and 0, 1, 2, 2, 2, and 1 QEIs were found to be significantly associated with GW in MC (GW-MC), GL-MC, TGW-MC, GW-RR, GL-RR, and TGW-RR, respectively.

Combinations of Ghd7, Ghd8, and Hd1 determine strong heterosis of commercial rice hybrids in diverse ecological regions.

Heterosis of grain yield is closely associated with heading date in crops. Gene combinations of the major heading date genes Ghd7, Ghd8, and Hd1 play important roles in enhancing grain yield and adaptation to ecological regions in rice. However, the predominant three-gene combinations for a specific ecological region remain unclear in both three-line and two-line hybrids.

Artificial Selection in Domestication and Breeding Prevents Speciation in Rice.

Speciation has long been regarded as an irreversible process once the reproductive barriers had been established. However, unlike in natural populations, artificial selection might either accelerate or prevent speciation processes in domesticated species. Asian cultivated rice is a target crop for both domestication and artificial breeding; it contains two subspecies of indica and japonica, which usually produce sterile inter-subspecific hybrids due to reproductive barriers.

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

Background: Breeding two-line hybrid rice with disease resistance is an effective approach to stabilize rice yield in commercial rice production of China.

Results: We improved the blast and bacterial blight resistance of Guangzhan63-4S, an elite photoperiod- and thermo-sensitive male sterile (P/TGMS) line widely used in two-line hybrid rice, by introducing the R genes Pi2 and Xa7 conferring resistance to rice blast and bacterial blight, respectively. Through the backcrossing and gene pyramiding breeding coupled with molecular marker-assisted selection, a new P/TGMS line Hua1228S carrying Pi2, Xa7, and tms5 was developed.

Three representative inter and intra-subspecific crosses reveal the genetic architecture of reproductive isolation in rice.

Systematic characterization of genetic and molecular mechanisms in the formation of hybrid sterility is of fundamental importance in understanding reproductive isolation and speciation. Using ultra-high-density genetic maps, 43 single-locus quantitative trait loci (QTLs) and 223 digenic interactions for embryo-sac, pollen, and spikelet fertility are depicted from three crosses between representative varieties of japonica and two varietal groups of indica, which provide an extensive archive for investigating the genetic basis of reproductive isolation in rice. Ten newly detected single-locus QTLs for inter- and intra-subspecific fertility are identified.

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

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.