RESUMEN
Oiltea-camellia (C. oleifera) is a widely cultivated woody oil crop in Southern China and Southeast Asia. The genome of oiltea-camellia was very complex and not well explored. Recently, genomes of three oiltea-camellia species were sequenced and assembled, multi-omic studies of oiltea-camellia were carried out and provided a better understanding of this important woody oil crop. In this review, we summarized the recent assembly of the reference genomes of oiltea-camellia, genes related to economic traits (flowering, photosynthesis, yield and oil component), disease resistance (anthracnose) and environmental stress tolerances (drought, cold, heat and nutrient deficiency). We also discussed future directions of integrating multiple omics for evaluating genetic resources and mining key genes of important traits, and the application of new molecular breeding and gene editing technologies to accelerate the breeding process of oiltea-camellia.
RESUMEN
The two-line rice hybrid "Super 1000" (GX24S × R900) represents a major landmark achievement of breeding for super-hybrid rice in China. However, both male parent R900 and hybrid "Super 1000" have an obvious defect of high susceptibility to rice bacterial blight (BB) and blast. Thus, improving disease resistance and maintaining the original high-yield capacity are essential for the sustainable application of "Super 1000." In this study, the application of closely linked single-nucleotide polymorphism (SNP) markers for foreground selection of dominant resistance gene loci together with genome-wide SNP markers for the background selection rapidly improved the disease resistance of R900 without disturbing its high-yield capacity. A series of improved R900 lines (iR900, in BC2Fn and BC3Fn generations) were developed to stack resistance genes (Xa23+Pi9, Xa23+Pi1+Pi2/9) by marker-assisted backcrossing and field selection for phenotypes, and further crossed with the female line GX24S to obtain improved hybrid variety Super 1000 (iS1000). The genetic backgrounds of iS1000 and "Super 1000" were profiled by using a 56 K SNP-Chip, and results showed that they shared 98.76% of similarity. Meanwhile, evaluation of the field disease resistance showed that the iR900 lines and iS1000 hybrids possess significantly enhanced resistance to both BB and rice blast. Resistance spectrum assays revealed that the iR900 lines and their derived hybrids exhibited high-level resistance to 28 Xoo strains tested, and enhanced resistance to leaf blast at the seedling stage when infected with 38 Magnaporthe oryzae isolates. Between 2019 and 2020, the multi-location field trials across the middle and lower reaches of the Yangtze River were launched and showed that the iS1000 slightly out-yielded than the original variety. In a large-scale demonstration site (6.73 ha, Yunnan, China), the iS1000 achieved 17.06 t/hm2 of yield in 2019. Moreover, the high similarity was observed in main agronomic traits and grain quality when comparing the improved lines/hybrids to original ones (iR900 vs. R900, iS1000 vs. S1000). This work presented a typical genomics-assisted breeding strategy and practice, which involves in directional introgression and rapid stack of multiple disease resistance genes, endowing the super-high-yield hybrid rice variety with holistic disease resistance but without yield penalty.
RESUMEN
Genomic selection is an efficient tool for breeding selection, especially for quantitative traits controlled by multiples genes with low heritability. To validate the application of genomic selection in hybrid rice breeding, the yield and grain quality traits of 404 hybrid rice breeding lines were investigated, and the same accessions were genotyped by using a 56 K SNP chip. There were wide variances among the tested accessions for all the measured traits, and most of the traits were correlated. A total of 67 significant loci were identified for the yield-related traits, and 123 significant loci were identified for the grain quality traits by GWAS. Two of these loci associated with increasing grain yield but decreasing grain quality. The GEBVs of all the yield and grain quality traits were calculated by using 15 different prediction algorithms. The plant height, panicle length, thousand grain weight, grain length and width ratio, amylose content, and alkali value have higher predictability than other traits. However, the predictive accuracy of different GS models is different for different traits. This study provided useful information for genomic selection of specific trait using proper markers and prediction models. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-022-01289-6.
RESUMEN
Revealing genomic variation of representative and diverse germplasm is the cornerstone of deploying genomics information into genetic improvement programs of species of agricultural importance. Here we report the re-sequencing of 239 japonica rice elites representing the genetic diversity of japonica germplasm in China, Japan and Korea. A total of 4.8 million SNPs and PAV of 35,634 genes were identified. The elites from Japan and Korea are closely related and relatively less diverse than those from China. A japonica rice pan-genome was constructed, and 35 Mb non-redundant novel sequences were identified, from which 1131 novel genes were predicted. Strong selection signals of genomic regions were detected on most of the chromosomes. The heading date genes Hd1 and Hd3a have been artificially selected during the breeding process. The results from this study lay the foundation for future whole genome sequences-enabled breeding in rice and provide a paradigm for other species.
