Breeding Science最新文献

Over the last several years, foot rot caused by Diaporthe destruens has become the most destructive sweetpotato disease in the southernmost region of Japan. Breeding of cultivars resistant to foot rot is required for effective and low-cost management. Field tests are often used to evaluate resistance of cultivars, but this approach has several limitations, including a long test period of several months and the requirement of field isolation and labor-intensive procedures. To minimize these issues, we have developed an easier and faster laboratory method using stem cuttings for the resistance test by optimizing four parameters: the number of unfolded leaves per cuttings, the positions of stems from which a cutting was prepared, the adequate number of culture days after inoculation, and the density of conidia of D. destruens at inoculation. Significant correlation was detected between the resistance indices of the laboratory test and the field test, namely, the length of the rotted part of a stem and the proportion of the plants rotted at the basal part of a stem, respectively. These results indicated that the laboratory test could indirectly evaluate the foot rot resistance of sweetpotato stems in the field and will be helpful to breed resistant cultivars.

Hybrid breakdown is a post-zygotic reproductive isolation that hinders genetic exchange between species or populations in both animals and plants. Two complementary recessive genes, temperature sensitive hybrid breakdown1 (thb1) and thb2, cause hybrid breakdown in rice (Oryza sativa). The present study delimited the THB1 locus to a 9.1-kb sequence, containing a single gene encoding a putative transmembrane protein with unknown functions. Haplotype analysis of THB1 in the two core collections of 119 accessions revealed that these accessions were divided into 22 haplotypes. A test cross with thb2 carrier showed that haplotype2 (H2) was assigned to thb1 and was restricted to temperate japonica. A nonsynonymous nucleotide polymorphism (SNP) specific to H2 was identified as a causal mutation in thb1. A test cross with thb1 carrier indicated that six accessions, including temperate japonica, tropical japonica, and indica, carried thb2. These results suggest that thb1 has recently evolved in temperate japonica, whereas thb2 arose in an ancient japonica and introgressed into the present three subgroups. Furthermore, we developed a derived cleaved amplified polymorphic sequence (dCAPS) marker to detect causal SNP in THB1. Our findings provide new insights into reproductive isolation and may benefit rice breeding.

This study focused on cucumbers' multi-pistillate flower (MPF) trait, which is essential for high yields. A genetic linkage map was constructed using a population of 219 F₂ plants to analyze quantitative trait loci (QTL) associated with MPF traits. Crossbreeding of EWSCU-809 (MPF) with EWSCU-989 (single pistillate flower: SPF) generated an F₁ hybrid that self-pollinated to form an F₂ population. Based on 244 single nucleotide polymorphic markers across seven cucumber chromosomes, a linkage map facilitated QTL analysis considering average pistillate flowers (PFs) per node and nodes with MPF traits. The results indicated a 9:6:1 epistatic ratio in the F₂ populations, revealing recessive allele control of the MPF trait in gynoecious plants. Three QTLs (qMP2.1, qMP3, qMP7) on chromosomes 2, 3, and 7 were associated with average PFs per node, explaining 5.6 to 10.3% of phenotypic variation. Four QTLs (qMP2.2, qMP3, qMP4, qMP7) on chromosomes 2, 3, 4, and 7 were linked to the presence of nodes with MPF traits, explaining 5.8 to 10.6% of phenotypic variance. Notably, QTL regions overlapped between the two datasets, suggesting pleiotropic effects, particularly on chromosomes 3 and 7. These reliable QTLs have the potential to improve breeding programs, enhance PF development, and increase cucumber yields.

The brown planthopper (BPH; Nilaparvata lugens Stål) is a devastating pest that causes severe rice yield losses in Asia. Introducing multiple BPH resistance genes into rice cultivars is an effective and sustainable way to mitigate yield losses. A traditional rice cultivar, 'Rathu Heenati', has durable BPH resistance due to multiple resistance genes (including BPH3 and BPH17) and quantitative trait loci (QTLs). However, these genes have not been used in Japanese rice breeding owing to limited genetic information. To identify markers tightly linked to BPH3 and BPH17 introgressed into the 'Sagabiyori' (susceptible) genetic background, we performed substitution mapping. BPH3 was delimited between RM3132 and RM589 on chromosome 6, and BPH17 between RM16493 and RM16531 on chromosome 4. We also performed QTL analysis to identify additional BPH resistance genes from 'Rathu Heenati' and detected a QTL, denoted as qBPH3.1, on chromosome 3. The effect of pyramiding BPH3 and BPH17 was significantly greater against virulent BPH populations than that of either gene alone. The combination of BPH3, BPH17 and qBPH3.1 from 'Rathu Heenati' might be facilitated to improve commercial Japanese cultivars with more robust BPH resistance.

As an essential grain, oil, and feed crop worldwide, soybean plays a crucial role. Developing high-yielding and high-quality soybean varieties is a critical goal for breeders. The grain weight per plant and 100-grain weight directly impact the soybean yield. This study combined genotypic data from the population with phenotypic data. Based on genome-wide association analysis (GWAS), GLM and MLM analysis models were used to locate the Gm04_21489088, Gm04_15703616, and Gm04_46466250 are loci related to soybean grain weight per plant, and find the Gm09_20334173, Gm04_39518612 and Gm04_39518624 are loci related to 100-seed weight. After performing a reference comparison, we conducted gene annotation and identified candidate genes Glyma.04G203400 and Glyma.04G125600, potentially associated with grain weight per plant in soybeans. These genes are primarily involved in protein synthesis and cell differentiation processes. The candidate gene Glyma.09G109100, associated with the 100-grain weight trait, was successfully annotated. The analysis revealed that the gene primarily involves enzyme activity, suggesting its potential role in regulating grain weight. These findings offer valuable insights into the mechanism of soybean yield and serve as a critical theoretical foundation and genetic resource for cultivating new soybean germplasm with high yield. These findings are of immense significance for future research endeavors to achieve high-yielding soybean varieties.

Pearl millet (Pennisetum glaucum (L.) R. BR.) is a cereal crop mainly grown in India and sub-Saharan Africa. In pearl millet, genes and genomic regions associated with traits are largely unknown. Pearl millet parental lines bred at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) are useful for the production and breeding of pearl millet. However, the phenotypic diversity of these lines has not been fully evaluated. In this study, 16 traits of 107 of those parental lines were assessed with field trials in Japan, and a genome-wide association study (GWAS) was performed using these phenotypic data to identify the genomic regions and genes associated with those traits. The GWAS revealed genomic regions associated with culm height and pigmentation of the shoot basal part (PS). The genomic region associated with PS contained a homolog of PHENYLALANINE AMMONIA LYASE 2 (PAL2), a gene involved in anthocyanin accumulation in Arabidopsis thaliana. The PAL2 homolog can be a candidate for a gene involved in regulating PS in pearl millet. These results provide a better understanding of the phenotypic diversity of pearl millet and its genetic background.

An experiment was conducted comprising of six corn hybrids that were subjected to drought and irrigated environment in separate columns in soil-plant-atmosphere-research (SPAR) cubes. The treatments and hybrids in SPAR cubes were replicated four times and a two factorial randomized complete block design (RCBD) was used to analyze the effect of drought on hybrids and their effects on traits. Significant drought × hybrid interactions were observed for most of the parameters. All the traits observed under this study were affected by drought conditions. Root volume (RV) and root shoot ratio (RSR) increased, and number of root tips (NRT), number of root forks (NRF), and number of root crossings (NRC) were drastically reduced under drought conditions. The photosynthetic rate (Phot) declined by 57.96% and electron transport rate (ETR) by 54.60% and was negatively correlated with plant height (PH) and root number (RN) during drought stress. Chlorophyll content (SPAD) showed a non-significant correlation with all the traits. As per results, there were significant differences among corn hybrids for different traits studied under the SPAR setup, which indicates that this setup successfully creates differences in treatments. A cumulative drought stress response index (CDSRI) was worked out. DKC-6581 and N61X-3110 were found to be highly drought tolerant as per our findings.

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.