Genetic diversity of Japanese sugar beet elite inbred line diversity (JSBDIV) set consisting of 63 lines was investigated using 33 cleaved amplified polymorphic sequence and 38 simple sequence repeat analyses. JSBDIV set was significantly subdivided into six (pedigree information), seven (Neighbor-Joining method) or 12 (population structure analysis) groups. The highest value of a pairwise population differentiation estimate, ΦPT value, among groups was yielded from population structure analysis with explained variation 32%. Some of the groups defined in this study exhibited close association with ancestral open-pollinated varieties (OPVs), suggesting that inter-OPV cross was rare during the establishment of JSBDIV set. On the other hand, low ΦPT values between some groups suggest that genetic backgrounds of ancestral OPVs had historically overlapped to some extent. Phenotypic traits showed significant differences both among and within groups. A nearly identical group was identified as the highest sugar content group irrespective of the grouping methods. Groups with Aphanomyces root rot resistance are associated with an OPV ‘Tmm-1’, suggesting it as a source of this trait. ‘Tmm-1’ is also associated with Cercospora leaf spot resistance, but an exceptional resistant line with no association of ‘Tmm-1’ supports a notion that different genetic resources exist for this trait.
To unveil the mechanism of the compatibility of odd-allotetraploid lily (LAAA) as female with diploid male lily, the differences of expressed unigenes in the ovaries and leaves between LAAA × AA and LAAA × LL were investigated using transcriptome analysis. The results showed the fruits of LAAA × AA well developed, while those of LAAA × LL aborted. The number of differentially expressed genes was less in the ovaries of LAAA × AA than those of LAAA × LL, but it showed opposite trend in those of leaves. The unigenes related with auxins, cytokinins, gibberellins, antioxidants, expansins, chlorophylls, carbohydrates, transport proteins were usually up-expressed in the ovaries and leaves of LAAA × AA but not in LAAA × LL; while those of abscisic acid, ethylene, jasmonic acid, and salicylic acid were increased in the ovaries or leaves of LAAA × LL but not in LAAA × AA. The up-expressed unigenes in the ovaries and leaves of LAAA × AA played positive roles in its fruit development because the products of the genes, like phytohormones and antioxidants, had functions protecting leaves from senescence or scavenging ROS, and thus LAAA was compatible with AA, while those of LAAA × LL played negative roles and caused its fruits aborted, and hence LAAA was incompatible with LL.
The Mutsu-Isuzu cytoplasmic male sterility (MI CMS) system is one of the three-line hybrid systems used in China. As we know, the hybrid system is tightly associated with the yield variation in F1 heterosis, while the restorer gene for the MI CMS (Rfm) has not been finely mapped for further application in marker-assisted selection (MAS). In this study, the sets of near-isogenic lines (NILs) of Rfm in two different genetic backgrounds were hybridized with the genome-wide 60 K single-nucleotide polymorphism (SNP) chip of Brassica for screening the possible associated genomic region of Rfm. Through screening genotypes with SNP loci and sequencing the candidate loci, one 2.5 Mb physical region (covering three scaffolds) on chrA09 was identified as the candidate for the Rfm region. Then, the SSR markers for the target scaffolds were used to detect the recombination in an F2 population and narrowed the Rfm gene within the genetic distance of 0.52 cM, equivalent to a 350 kb physical segment. Moreover, the markers were tested to improve new elite restoration lines and to assess the percentage of hybrid seeds. Our results could potentially accelerate the map-based cloning of the Rfm gene to benefit rapeseed breeding.
Soybean (Glycine max) seeds are prone to imbibition injury caused by a rapid uptake of water. Genetic variation in imbibition injury tolerance is well documented, but the underlying mechanisms remain unclear. The aim of this study was to clarify the role of the aleurone layer of seed coat in the tolerance and its structural differences between tolerant and susceptible cultivars. Imbibition injury tolerance was closely related to the water absorption rate of seeds, which was regulated by the aleurone layer of the seed coat. Cryo-scanning electron microscopy analysis revealed that water absorbed in seed coats entered the seed preferentially through the aleurone layer of the top area above the raphe. In susceptible cultivars, the cell walls of the aleurone layer facing the cotyledon in this area were thin and the surface showed shallow depression-like structures, a distinct structure different from those of the tolerant cultivars, which had aleurone cells with thick outer cell walls and smooth and stripe-like deposits. The differences in the structural features of the cell walls and surfaces of aleurone cells in the top area of the seed may be responsible for the difference in the extent of imbibition injury between susceptible and tolerant cultivars.
To evaluate and utilize potentially valuable quantitative trait loci or genes of wild relatives in the genetic background of domesticated crop species, chromosome segment substitution lines (CSSLs) are a valuable tool. CSSLs can be constructed through the exchange of chromosome segments of AA genome species of the genus Oryza with cultivated rice, Oryza sativa L. Here we report the development of three sets of CSSLs carrying segments of AA genome species closely related to Oryzasativa—O. glaberrima (IRGC 103777 from Mali), O. rufipogon (W1962 from China), and O. nivara (IRGC 105715 from Cambodia)—in the genetic background of ssp. japonica cultivar Taichung 65 through the use of 101 to 121 simple-sequence-repeat markers in whole-genome genotyping and marker-assisted selection. The materials are available via the National Bioresource Project (Rice) Oryzabase Web page.
DNA methylation is an epigenetic modification that can affect gene expression and transposable element (TE) activities. Because cytosine DNA methylation patterns are inherited through both mitotic and meiotic cell divisions, differences in these patterns can contribute to phenotypic variability. Advances in high-throughput sequencing technologies have enabled the generation of abundant DNA sequence data. Integrated analyses of genome-wide gene expression patterns and DNA methylation patterns have revealed the underlying mechanisms and functions of DNA methylation. Moreover, associations between DNA methylation and agronomic traits have also been uncovered. The resulting information may be useful for future applications of natural epigenomic variation, for crop breeding. Additionally, artificial epigenome editing may be an attractive new plant breeding technique for generating novel varieties with improved agronomic traits.
IR64 is one of the world’s most popular rice cultivars. To collect genetic factors involved in controlling its heading date, we developed 70 reciprocal advanced-backcross populations with a total of 6284 individuals at the BC4F2 generation from crosses between Koshihikari and IR64. We detected 29 QTLs associated with heading date on chromosomes 3, 5–8, 10, and 12. Twenty QTLs were located in the same chromosome regions as previously isolated heading date genes (Hd1, Hd6, Hd16, Ghd7, DTH8, Hd17, and Hd18). The rest were located in other chromosome regions. We found more number of QTLs than previous studies using mapping populations of IR64. Fine mapping in additional advanced-backcross populations clearly revealed that QTLs on the long arm of chromosome 7 are overlapping and seem to be a novel genetic factor for heading date because of their different locations from OsPRR37. Our results suggest that the difference in heading date between IR64 and Koshihikari is genetically controlled by many factors, and that a non-functional allele of Hd1 contributes to early heading of IR64 in the genetic background of functional alleles of other heading date QTLs and genes such as Hd6 and Hd16.
The fusarium yellows resistance (YR) gene FocBo1was previously identified and the DNA markers were developed to assist the breeding of YR cultivars in Brassica oleracea. However, the further analysis revealed discrepancies between the phenotypes and the genotypes predicted by those DNA markers in cabbage commercial cultivars. Since this discrepancy seemed to be due to unknown susceptible alleles of focbo1, we sequenced the gene in 19 accessions to determine the sequence variations between alleles and found that there were two resistant FocBo1 alleles and six susceptible alleles in the investigated population. The newly designed PCR markers detected three mutations in the susceptible alleles that generate premature termination codons. These were shown to accurately distinguish resistant and susceptible alleles in more than 200 accessions of B. oleracea inbred lines and cultivars. The study revealed that the locus is represented by 37.2% resistant and 62.8% susceptible alleles within seventy-eight commercial cultivars. Structural analysis of the gene revealed that a part of the allelic variation comes from intragenic recombination between alleles. Our results enable a more precise prediction of the phenotype by marker assisted selection, promoting the production of YR cultivars in B. oleracea.
We assessed genetic variation in rice germplasm in northern Laos and Vientiane province from polymorphism data of SSR markers. We classified 314 accessions into three clusters; Ia (corresponding to the lowland Japonica Group), Ib (upland Japonica Group) and II (Indica Group). The accessions of cluster Ib grew mainly in mountainous fields, and those of cluster II grew commonly in basins and along rivers. The few accessions of cluster Ia grew in only three provinces: Houaphanh, Xiangkhouang and Vientiane. Lowland cultivars in cluster II were predominant in Vientiane. Variations in heading date under short-day conditions in 2014 and long-day conditions in 2015 indicate that many accessions were sensitive to the photoperiod on account of complex genetic mechanisms underlying both photoperiod sensitivity and basic vegetative growth. A total of 219 among whole accessions were classified into 6 groups: E1–3 and L1–3. E2 and E3 were dominant in clusters Ib and II; E1 and L1–3 were minor groups. These results demonstrate characteristic distributions of the Indica and Japonica Group’s germplasms in northern Laos and their genetic variation in heading date.
Food contamination by cadmium (Cd) is a serious threat to human health. Thus, it is imperative to prevent Cd accumulation in staple crops like soybean. The development of low Cd accumulating cultivars is an effective solution. To this end, it is essential to identify the gene(s) controlling seed Cd accumulation. Although Glyma.09G055600 (GmHMA3) seems to be associated with Cd accumulation in soybean, it has not been established if it is responsible for seed Cd accumulation. In the present study, the effect of GmHMA3 on seed Cd accumulation in soybean was validated using three independent GmHMA3 mutants isolated from an ethyl methanesulfonate-induced soybean mutant library. Each of mutant had an amino acid substitution in GmHMA3 and segregating progenies were developed by crossing the original cultivar with each of the three mutants. The relationship between these three mutations and seed Cd accumulation was investigated. While two of them significantly increased seed Cd accumulation corresponding to previous reports of a natural missense mutation in GmHMA3, the other slightly decreased seed Cd accumulation. Overall, these results indicate that GmHMA3 is responsible for seed Cd accumulation in soybean.
High oleic acid composition is an important determinant of seed quality in peanut (Arachis hypogaea) in regard to its nutritional benefits for human health and prolonged shelf-life for peanut products. To improve the oleic acid content of popular peanut cultivars in China, four peanut cultivars of different market types were hybridized with high-oleic-acid donors and backcrossed for four generations as recurrent parents using fad2 marker-assisted backcross selection. Seed quality traits in advanced generations derived by selfing were assessed using near-infrared reflectance spectroscopy for detection of oleic acid and Kompetitive allele-specific PCR (KASP) screening of fad2 mutant markers. Twenty-four high-oleic-acid lines of BC4F4 and BC4F5 populations, with morphological features and agronomic traits similar to those of the recurrent parents, were obtained within 5 years. The genetic backgrounds of BC4F5 lines were estimated using the KASP assay, which revealed the genetic background recovery rate was 79.49%–92.31%. The superior lines raised are undergoing a multi-location test for cultivar registration and release. To our knowledge, this is the first application of single nucleotide polymorphism markers based on the high-throughput and cost-effective KASP assay for detection of fad2 mutations and genetic background evaluation in a peanut breeding program.
Although some studies have been conducted on the effects of foreign protein expression on rice, the results vary with foreign gene types and protein expression. This study reveals the effects of fibroblast growth factor 21 (FGF21) expression on mature rice seeds in various aspects. Results revealed that the grain weight of the transgene rice was lower than that of non-transgenic wild-type. The sucrose content and ADP-glucose pyrophosphorylase (AGPase) activity in transgenic FGF21 rice were higher than that in non-transgenic wild-type rice, while changes in the starch content, starch branching enzyme (SBE), sucrose synthase (SuS), superoxide dismutase (SOD) and peroxidase (POD) activity were lower in transgenic FGF21 rice compared to non-transgenic wild-type. The scanning electron microscope results revealed that mature seeds of the transgenic FGF21 rice contained fewer vascular bundles with irregular arrangement compared to the wild-type. The mature seeds of CK and T1 rice lines were collected for proteome analysis, and 167 differentially expressed proteins (DEPs) were found. In addition, the most enriched pathways in both rice lines were determined to be amino sugar and nucleotide sugar metabolism and starch and sucrose metabolism, etc. This study laid the foundation for revealing the effects of exogenous protein expression on rice bioreactors.
Genomic selection (GS) is the one of the new method for molecular marker-assisted selection (MAS) that can improve selection efficiency and thereby accelerate selective breeding progress. In the present study, we used the exotic germplasm LK1 to improve the shelling percentage of Qi319 by GS. Genome-wide marker effects for each trait were estimated based on the performance of the testcross and SNP data for F2 progenies in the training population. The accuracy of genomic predictions was estimated as the correlation between marker-predicted genotypic values and phenotypic values of the testcrosses for each trait in the validation population. Our study result indicated that selection response for shell percentage was 33.7%, which is greater than those for grain yield, kernel number per ear, or grain moisture at harvest. Selection response for tassel branch number and weight per 100 kernels was greater than 60%. The Higher trait heritability resulted in better prediction efficiency; Prediction accuracy increased with the training population size; Prediction efficiency did not differ significantly between SNP densities of 1000 bp and 55,000 bp. The results of the present research project will provide a basis for genome-wide selection technology in maize breeding, and lay the groundwork for the application of GS to germplasms that are useful in China.
Direct seeding of rice often results in poor crop establishment due to unlevelled fields, unpredicted heavy rains after sowing, and weed and pest invasion. Thus, it is important to develop varieties able to tolerate flooding during germination, also known as anaerobic germination (AG), to address these constraints. A study was conducted to identify QTLs associated with AG tolerance from an IR64/Kharsu 80A F2:3 mapping population using 190 lines phenotyped for seedling survival under the stress. Genotyping was performed using a genome-wide 384-plex Indica/Indica SNP set. Four QTLs derived from Kharsu 80A providing increased tolerance to anaerobic germination were identified: three on chromosome 7 (qAG7.1, qAG7.2 and qAG7.3) and one on chromosome 3 (qAG3), with LOD values ranging from 5.7 to 7.7, and phenotypic variance explained (R2) from 8.1% to 12.6%. The QTLs identified in this study can be further investigated to better understand the genetic bases of AG tolerance in rice, and used for marker-assisted selection to develop more robust direct-seeded rice varieties.
To overcome a limitation to the breeding of autogamous crops, recurrent selection using transgenic male sterility (RSUTMS) has been proposed. In this system, negatively or positively selectable marker traits are required along with dominant transgenic male sterility. Anthocyanin pigmentation is an excellent marker trait. Two regulatory genes forMYB and bHLH and a structural gene for DFR are required for anthocyanin pigmentation in rice. Therefore, to apply anthocyanin pigmentation as a marker trait in various rice genotypes, coordinated expression of the three genes is required. In this study, we developed a leaf sheath–specific promoter and introduced three genes—DFR and C1/Myb, driven by the 35S promoter, and OsB2/bHLH, driven by the leaf sheath–specific promoter—into the rice genome. Leaf sheath–specific pigmentation was confirmed in all seven genotypes tested, which included japonica and indica cultivars. Analysis of genome sequence data from 25 cultivars showed that the strategy of conferring leaf sheath–specific anthocyanin pigmentation by introduction of these three genes would be effective for a wide range of genotypes and will be applicable to RSUTMS.