Breeding Science最新文献

Heading date (HD) is a crucial agronomic trait, controlled by multiple loci, that conditions a range of geographical and seasonal adaptations in rice (Oryza sativa L.). Therefore, information on the HD genotypes of cross parents is essential in marker-assisted breeding programs. Here, we used the Fluidigm 96-plex SNP genotyping platform to develop genotyping assays to determine alleles at 41 HD loci (29 previously characterized genes and 12 quantitative trait loci [QTLs], including a newly detected QTL). The genotyping assays discriminated a total of 144 alleles (defined on the basis of the literature and publicly available databases) and QTLs. Genotyping of 377 cultivars revealed 3.5 alleles per locus on average, a higher diversity of Hd1, Ghd7, PRR37, and DTH8 than that of the other loci, and the predominance of the reference ('Nipponbare') genotype at 30 of the 41 loci. HD prediction models using the data from 200 cultivars showed good correlation (r > 0.69, P < 0.001) when tested with 22 cultivars not included in the prediction models. Thus, the developed assays provide genotype information on HD and will enable cost-effective breeding.

Combining high-throughput genotyping data with the latest wheat genomic information provided more detailed information on the genetic diversity of the Japanese wheat core collection (JWC). Analysis of genomic population structure divided the JWC accessions into three populations: northeast Japan accessions, native and southwest Japan accessions, and modern accessions showing mixed breeding patterns. This indicates that Japanese wheat varieties have a background of native genomes from southwest Japan incorporating valuable genes from various exotic lines, which is supported by the history of Japanese wheat breeding. Association analyses of several agronomic traits have revealed how genes or alleles have been selected in Japanese wheat breeding and how they differ from those in other regions of the world. This analysis of the JWC collection is expected to contribute not only to the elucidation of genetic diversity in Japanese wheat accessions but also to future wheat breeding by providing a new genetic resource.

The awn is a bristle-like appendage that protrudes from the seed tip and plays a critical role in preventing feed damage and spreading habitats in many grass species, including rice. While all wild species in the Oryza genus have awns, this trait has been eliminated in domesticated species due to its obstructive nature to agricultural processes. To date, several genes involved in awn development have been identified in wild rice, Oryza rufipogon and Oryza barthii which are ancestral species of cultivated rice in Asia and Africa, respectively. However, the responsible genes for awn development have not been identified in other wild rice species even though multiple QTLs have been reported previously. In this study, we identified An7 gene responsible for awn development in two wild rice species, Oryza glumaepatula and Oryza meridionalis. An7 encodes a cytochrome P450 enzyme and is homologous to D2/CYP90D2, a known brassinosteroid biosynthesis enzyme in rice. The identification of An7 provides insight into a distinct molecular mechanism underlying awn development that occurs in geographically separated environments.

Wheat yellow mosaic disease is a soilborne disease caused by wheat yellow mosaic virus (WYMV). Symptoms include yellow mosaic coloring of leaves, stunting, and growth inhibition. Here we conducted a detailed analysis of resistance to this virus in winter wheat 'Hokkai 240' by carrying out inoculation tests of WYMV and conducting field tests. The resistance level observed in 'Hokkai 240' was compared with those in varieties harboring known resistance genes. In the inoculation tests, 'Hokkai 240' showed resistance to WYMV Pathotypes I and II and partial resistance to Pathotype III. This result was contrary to the sensitive responses to the three pathotypes exhibited by the variety harboring resistance gene on chromosome 2DL. In fields infected with WYMV Pathotypes II and III, 'Hokkai 240' plants exhibited few disease symptoms and little proliferation of the virus. By analyzing the quantitative trait loci (QTLs) in recombinant inbred lines from a cross between 'Hokkai 240' and 'Nanbukomugi', a single major QTL, Q.Ymhk, from 'Hokkai 240', which had significant effects on Pathotypes II and III of the virus, was detected in the proximity of snp4212 and snp4215 mapped on chromosome 2AS. These results indicate that Q.Ymhk may be useful for developing broad resistance to WYMV in wheat breeding programs.

Seed development is an essential phenomenon for all sexual propagative plant species. The functional allele at SEED DEVELOPMENT 1 (SDV1) or SEED DEVELOPMENT 2 (SDV2) loci is essential for seed development for Oryza sativa and Oryza meridionalis. In the present study, we performed fine mapping of SDV1, narrowing down the area of interest to 333kb on chromosome 6. Haplotype analysis around the SDV1 locus of O. meridionalis accessions indicated that they shared the DNA polymorphism, suggesting that they have a common abortive allele at the SDV1 locus. Linkage analysis of the candidate SDV2 gene showed that it was located on chromosome 4. The candidate SDV2 was confirmed using a population in which both the SDV1 and SDV2 genes were segregating. The chromosomal region covering the SDV1 gene was predicted to contain 30 protein-coding genes in O. sativa. Five of these genes have conserved DNA sequences in the chromosomal region of the SDV2 gene on chromosome 4, and not on chromosome 6, of O. meridionalis. These results suggest that these five genes could be candidates for SDV1, and that their orthologous genes located on chromosome 4 of O. meridionalis could be candidates for SDV2.

In mechanically harvested soybean, green stem disorder (GSD) is an undesirable trait that causes green-stained seeds, which are graded lower in Japan. To obtain DNA markers for reduced GSD, we conducted a quantitative trait locus (QTL) analysis for 2 years using F₄ and F₅ lines from a cross between 'Suzuotome' (less GSD) and 'Fukuyutaka' (more GSD). We validated the effect of a detected QTL for GSD by first identifying F₄ or F₅ plants in which one or more markers in the QTL region were heterozygous. The F₅ or F₆ progeny of each plant was used to form a pair consisting of two groups in which the QTL region was homozygous for either the 'Suzuotome' or 'Fukuyutaka' allele in a similar genetic background, and the two groups within each pair were compared for GSD. Over 3 years of testing, the 'Suzuotome' allele of a QTL on chromosome 6 was found to reduce the level of GSD. This novel QTL was mapped to the region around DNA marker W06_0130, and was not closely linked to QTLs for important agronomic traits including yield components. Using this marker, the low level of GSD from 'Suzuotome' could be conferred to 'Fukuyutaka' or other high-GSD cultivars.

Salt tolerance has been an important issue as a solution for soil salinization and groundwater depletion. To challenge this issue, genetic diversity of wild plants must be harnessed. Here we report a discovery of a candidate gene for salt tolerance in Vigna nakashimae, one of the coastal species in the genus Vigna. Using intraspecific variation, we performed a forward genetic analysis and identified a strong QTL region harboring ~200 genes. To further narrow down the candidate genes, we performed a comparative transcriptome analysis, using the genome sequence of azuki bean (V. angularis) as a reference. However the detected differentially-expressed genes (DEGs) did not include those related to salt tolerance. As we suspected that the target gene in V. nakashimae is missing in V. angularis, we sequenced the whole genome sequence of V. nakashimae with long-reads. By re-analyzing the transcriptome data with the new reference genome, we successfully identified POCO1 as a candidate gene, which was missing not only in V. angularis but also in the salt-sensitive accession of V. nakashimae. Further comparative analysis revealed that the tolerant genotypes conserved the ancestral form of the locus, while the sensitive genotypes did not. We also emphasize the pitfalls in our study, such as position effect in a growth chamber, missing important genes in the reference genome, and limited reproducibility of RNA-seq experiments.

DNA markers serve as essential tools in breeding selection and genetic analysis. However, developing DNA markers can be time-consuming and labor-intensive due to the need to identify polymorphisms between cultivars/lines and to design suitable primers. To address these challenges, we have developed DNAMarkMaker, a tool designed to automate the process of primer design for Amplification Refractory Mutation System (ARMS) and Cleaved Amplified Polymorphic Sequences (CAPS) markers, utilizing resequencing data. One key feature of DNAMarkMaker is its user-friendly graphical user interface (GUI), ensuring its accessibility and ease of use, even for researchers not well-versed in bioinformatics. We confirmed DNAMarkMaker's applicability by developing DNA markers for rice, potato, and turnip-each representing distinct genome structures: homozygous diploid, heterozygous autotetraploid, and heterozygous diploid, respectively. DNAMarkMaker will contribute to the rapid and efficient development of DNA markers, accelerating breeding and genetic analysis in various crops.

Flowering time is an important agronomic trait that is highly correlated with plant height, maturity time and yield in mungbean. Up to present, however, molecular basis of flowering time in mungbean is poorly understood. Previous studies demonstrated that flowering time in mungbean is largely controlled by a major QTL on linkage group 2 (LG2). In this study, the QTL on the LG2 in mungbean was investigated using F₂ and F_2:3 populations derived from a cross between mungbean cultivar Kamphaeng Saen 2 (KPS2) and wild mungbean accession ACC41. The QTL was narrowed down to a genome region of 164.87 Kb containing a phytochrome gene, designated VrPHYE, encoding phytochrome E (phyE), a known photoreceptor modulating flowering time. Compared to VrPHYE of the wild ACC41, VrPHYE of KPS2 contained several single nucleotide polymorphisms (SNPs) causing amino acid changes. Those SNPs were also found in other mungbean cultivars. Some amino acid changes were predicted to occur in the regulatory region of phytochromes. Gene expression analysis revealed that VrPHYE in KPS2 was expressed significantly higher than that in ACC41. These results showed that VrPHYE is the candidate gene controlling flowering time in the mungbean.

Data from breeding, including phenotypic information, may improve the efficiency of breeding. Historical data from breeding trials accumulated over a long time are also useful. Here, by organizing data accumulated in the National Agriculture and Food Research Organization (NARO) rice breeding program, we developed a historical phenotype dataset, which includes 6052 records obtained for 667 varieties in yield trials in 1991-2018 at six NARO research stations. The best linear unbiased predictions (BLUPs) and principal component analysis (PCA) were used to determine the relationships with various factors, including the year of cultivar release, for 15 traits, including yield. Yield-related traits such as the number of grains per panicle, plant weight, grain yield, and thousand-grain weight increased significantly with time, whereas the number of panicles decreased significantly. Ripening time significantly increased, whereas the lodging degree and protein content of brown rice significantly decreased. These results suggest that panicle-weight-type high-yielding varieties with excellent lodging resistance have been selected. These trends differed slightly among breeding locations, indicating that the main breeding objectives may differ among them. PCA revealed a higher diversity of traits in newer varieties.