Mapping and breeding value evaluation of a semi-dominant semidwarf gene in upland rice

Plant height is an important trait related to yield potential and plant architecture.A suitable plant height plays a crucial role in improvement of rice yield and lodging resistance.In this study,we found that the traditional upland landrace 'Kaowenghan'(KWH) showed a special semi-dwarf phenotype.To identify the semi-dwarf gene from KWH,we raised BC2 F4 semi-dwarf introgression lines(IL) by hybridization of the japonica rice cultivar 'Dianjingyou1'(DJY1) and KWH in a DJY1 background.The plant height of the homozygous semi-dwarf IL(IL-87) was significantly reduced compared with that of DJY1.The phenotype of the F1 progeny of the semi-dwarf IL-87 and DJY1 showed that the semi-dwarf phenotype was semidominant.QTL mapping indicated that the semi-dwarf phenotype was controlled by a major QTL q DH1 and was localized between the markers RM6696 and RM12047 on chromosome 1.We also developed near-isogenic lines(NIL) from the BC3 F3 population,and found that the yield of homozygous NIL(NIL-2)was not significantly different compared to DJY1.Breeding value evaluation through investigation of the plant height of the progeny of NIL(NIL-2) and cultivars from different genetic background indicate that the novel semi-dwarf gene shows potential as a genetic resource for rice breeding.

A hybrid sterile locus leads to the linkage drag of interspecific hybrid progenies

Interspecific hybridization plays an important role in rice breeding by broadening access to desirable traits such as disease resistance and improving yields.However,interspecific hybridization is often hindered by hybrid sterility,linkage drag,and distorted segregation.To mine for favorable genes from Oryza glaberrima,we cultivated a series of BC4 introgression lines(ILs)of O.glaberrima in the japonica rice variety background(Dianjingyou 1)in which the IL-2769(BC4F10)showed longer sterile lemmas,wider grains and spreading panicles compared with its receptor parent,suggesting that linkage drag may have occurred.Based on the BC5F2 population,a hybrid sterility locus,S20,a long sterile lemma locus,G1-g,and a new grain width quantitative trait locus(QTL),qGW7,were mapped in the linkage region about 15 centimorgan(cM)from the end of the short arm of chromosome 7.The hybrid sterility locus S20 from O.glaberrima eliminated male gametes of Oryza sativa,and male gametes carrying the alleles of O.sativa in the heterozygotes were aborted completely.In addition,the homozygotes presented a genotype of O.glaberrima,and homozygous O.sativa were not produced.Surprisingly,the linked traits G1-g and qGW7 showed similar segregation distortion.These results indicate that S20 was responsible for the linkage drag.As a large number of detected hybrid sterility loci are widely distributed on rice chromosomes,we suggest that hybrid sterility loci are the critical factors for the linkage drag in interspecific and subspecific hybridization of rice.

Natural alleles of a uridine 5'-diphospho-glucosyltransferase gene responsible for differential endosperm development between upland rice and paddy rice

Traditional upland rice generally exhibits insufficient grains resulting from abnormal endosperm development compared to paddy rice. However, the underlying molecular mechanism of this trait is poorly understood. Here,we cloned the uridine 5’-diphospho(UDP)-glucosyltransferase gene EDR1(Endosperm Development in Rice) responsible for differential endosperm development between upland rice and paddy rice by performing quantitative trait loci analysis and map-based cloning. EDR1 was highly expressed in developing seeds duringgrain filling. Natural variations in EDR1 significantly reduced the UDP-glucosyltransferase activity of EDR1 YZNcompared to EDR1 YD1,resulting in abnormal endosperm development in the near-isogenic line, accompanied by insufficient grains and changes in grain quality.By analyzing the distribution of the two alleles EDR1 YD1 and EDR1 YZNamong diverse paddy rice and upland rice varieties, we discovered that EDR1 was conserved in upland rice, but segregated in paddy rice. Further analyses of grain chalkiness in the alleles of EDR1 YD1 and EDR1 YZNvarieties indicated that rice varieties harboring EDR1 YZNand EDR1 YD1 preferentially showed high chalkiness, and low chalkiness,respectively. Taken together, these results suggest that the UDP-glucosyltransferase gene EDR1 is an important determinant controlling differential endosperm development between upland rice and paddy rice.

Interspecific Hybrid Sterility in Rice Is Mediated by OgTPR 1 at the S 1 Locus Encoding a Peptidase- like Protein

Dear Editor The Asian cultivated rice （Oryza sativa L. ssp japonica and ssp indica） is a staple food crop, and current rice breeding for the utilization of hybrid vigor （heterosis） mainly uses crosses within and between japonica and indica varieties （Chen and Liu, 2016）. However, another cultivated rice, African rice （Oryza glaberrima Steud）, has many important traits, such as tolerance to heat, drought, aluminum toxicity, and disease （Brar and Khush, 1997）. Hybrids from crosses between species, such as between African and Asian rice varieties, have stronger hybrid vigor and greater yield potential than those within subspecies;

Genome and Comparative Transcriptomics of African Wild Rice Oryza Iongistaminata Provide Insights into Molecular Mechanism of Rhizomatousness and Self-Incompatibility

Dear Editor, Oryza Iongistaminata is an African wild rice species with AA genome type possessing special traits that are highly valued for improving cultivated rice, such as strong resistance to biotic and abiotic stresses （Song et al., 1995） for improving resistance of cultivars, rhizomatousness for perennial breeding （Glover et al., 2010）, and self-incompatibility （SI） for new ways to produce hybrid seeds （Ghesquiere, 1986）. Deciphering the genome of O. Iongistaminata will be the key to uncovering the mechanism of these hallmark traits and improving cultivated rice.