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Additional index words. Brassica oleracea var. capitata, 'Zaoxia 16' (F1), codominant marker Abstract. Four molecular marker systems—RAPD (random amplified polymorphic DNA), ISSR (intersimple sequence repeat), SRAP (sequence-related amplified poly- morphism), and SSR (simple sequence repeat)—were used to evaluate seed genetic purity of a hybrid cabbage cultivar 'Zaoxia 16'. Genetic relationships of the F1 hybrids and their parents were analyzed with 157 RAPD primers, 54 ISSR primers, 84 SRAP primer combinations, and 44 SSR primers. Three RAPD primers (NAURP2006, NAURP2020, and NAURP2031), two ISSR primers (NAUISR1058 and NAUISR1062), one SRAP primer combination (NAUSR04/NAURS05), and two SSR primers (NAUSSR1011 and NAUSSR1031), which produced male and female parent-specific markers simulta- neously, were selected for testing the genetic purity of the F1 seeds. A total of 210 'Zaoxia 16' hybrid individuals were investigated with these eight selected primers. Of these, 12 appeared to be false hybrids. Nine of the 12 putative false hybrids, confirmed with all eight primers, exhibited similar banding patterns to the female parent, suggesting that they could be derived from selfing of the female parent. The results were in accordance with those from field evaluations. This study showed that RAPD, ISSR, SRAP, and SSR markers are highly efficient and reproducible for genetic purity testing of cabbage commercial hybrid seeds. more...

This study aims to establish the discrimination of F1 hybrid seeds from their parental lines and rapid selection of proteinrich lines from inbreeding lines of corn using FT-IR spectroscopy combined by multivariate analysis. Eight individual seeds from the maternal and paternal lines of Gwangpyeongok and their F1 progeny seeds were subjected to FT-IR spectroscopy. A total of 176 corn inbreeding lines including commercial corn cultivars were subjected to FT-IR spectroscopy. To establish the prediction model for total protein content from corn seed, 33 corn inbreeding lines out of 176 were randomly selected and total seed protein contents using Bradford assay were examined. PLS-DA (partial least square regression discriminant analysis) could clearly discriminate F1 hybrid seeds from their parental lines. PC (principal component) loading values show that 1,700 – 1,500 cm−1 and 1,200 – 900 cm−1 regions of FT-IR spectra are significantly important for discrimination of corn lines. The prediction model for total protein contents was established by PLS (partial least square regression) algorithm, and its accuracy was confirmed by cross-validation test (R2 = 0.94). After external validation fromexternal 25 corn inbreeding lines, regression coefficient (R2) was 0.78 which indicated that the prediction model had relatively good accuracy. Thus, considering these results we suggest that FT-IR combined with multivariate analysis could be applied as a novel tool for high-throughput screening of F1 hybrid seeds from their parental lines and protein-rich lines for breeding of silage corn cultivar. more...

Relevance. Biologically active compounds are widely used at the modern vegetable production, and especially at the seed production. Influence of Micephyt preparation in the mixed with Etrel is evaluated at the first time. The goal of the study is evaluation the effect of Micephyt in the mixed of Etrel on the obtaining of hybrid seeds of the squash ( Cucurbita pepo var. giramontia Duch.). Materials and methods . Studies were carried out at the experimental plot Transnistrian State University named T.G. Shevchenko (Tiraspol) during 2010-2012. The object of studies was maternal line F 1 (166/5x98/5) of squash (analog of commercial hybrid F 1 Lenutsa). Materials of study were preparations: Etrel (c= 0 and 300 ppm) and Micephyt in the mixed with Etrel (c= 10 and 100 ppm). There were 2 treatments of squash plants with these preparations: at the stage 2-3 leaves, and at the stage of 6-7 leaves. Results. Treatments maternal line of squash F 1 with mixed preparation “Etrel-300 ppm + Micephyt-10 ppm” show the positive effect on the seed productivity of plants. We observed the significant increasing main components of seed productivity during three years of study. The mass of 1000 seed was increased on 10.1%; the quantity of seed fruits was increased on 9.0%; the quantity of fruits on the plant was increased on 11.8% and the seed productivity was increased on 33.0%. Seed yields of F 1 squash were increased in 1.37 times on the standard (“Etrel-300 ppm”) after plant treatment with mixed preparation “Etrel-300 ppm + Micephyt-10 ppm”. High quality of seeds was maintained. The profitability of additional costs associated with the use of the preparation Micephit for the treatment of the maternal line 166/5 squash was 343%. So, the treatment of squash plants with mixed preparation “Etrel-300 ppm + Micephyt-10 ppm” is economic effective element the technology of F 1 squash hybrid seed production. more...

With increasing LM soybean import, the concern about unintentional gene flow from LM soybean to wild soybean and consequential weedy risk has been growing. Therefore, we conducted this study to characterize seed traits including germination of hybrids resulted from gene flow from LM soybean to wild soybean in comparison with their parents, LM soybean and wild soybean. Pollen-donor LM soybean seeds were much greater and heavier (about 15.0 g of 100 seed weight) than F2 hybrid (5.7 g), while pollen-recipient wild soybean and F1 hybrid seeds were smallest and lightest (about 2.5 g). F2 hybrid was brown, intermediate between yellow LM soybean seed and black wild soybean seed. These findings indicate that F1 hybrid seeds show similar characteristics with wild soybean, while F2 hybrid seeds show intermediate color and size between two parents. F2 hybrid seed showed intermediate traits between two parents in germination and dormancy rates, which were 35% and 65%, respectively. LM soybean showed no dormancy, while wild soybean showed greater than 90% dormancy. This finding indicates that F2 hybrid show intermediate characteristics in seed germination with high dormancy trait, suggesting a potential weediness of hybrids resulted from gene flow from LM soybean to wild soybean. more...

Cabbage (Brassica oleracea L. var. capitata) is an important vegetable worldwide. Most Japanese commercial cultivars of cabbage use an F1 hybrid seed production system. The purity of F1 hybrid seeds is important and the assessment of purity based on DNA markers can be highly accurate. In addition, selection of agronomically important traits such as disease resistance based on DNA markers is useful for breeding of cabbage. The aim of this study is to demonstrate the effectiveness of DNA marker-assisted selection in cabbage. In this study we distinguished the parental S haplotypes in 35 F1 hybrid cultivars by combining several linked DNA markers. Thirty-one highly polymorphic simple sequence repeats (SSR) markers were screened from 175 reported SSR markers, which are useful for assessment of the purity of F1 hybrid seeds. We examined the relationship between the DNA marker based genotype and the phenotype by an inoculation test of clubroot disease. A co-dominant PCR–RFLP marker was developed for selection of Fusarium yellows resistance and the genotypes using this marker were consistent with inoculation test in all tested samples. more...

The hybrid purity of melon (Cucumis melo L.) was tested by polymerase chain reaction (PCR) assay based on simple sequence repeat (SSR) markers in two F1 melon hybrids (‘Dongfangmi 1’ and ‘Dongfangmi 2’) and their parental lines. Twelve pairs of SSR primers for ‘Dongfangmi 1’ and three pairs for ‘Dongfangmi 2’ were selected. Results showed that self-inbred seeds were effectively distinguished from F1 hybrid seeds using these SSR primers, a finding that was consistent with the results recorded from field tests. ‘Dongfangmi 1’ and ‘Dongfangmi 2’ were identified from their parental lines, and seven other uterine hybrid lines by multiplex primers MS48+MS60 and MS4+MS20, respectively. Contamination of F1 hybrid seeds caused by self-inbred and other unknown pollens can be effectively and more reliably detected by PCR assays with multiplex SSR primers. more...

Self-incompatibility as well as male sterility is successfully used for the production of F1 hybrid seeds in Brassica vegetables. Since the first commercial F1 hybrid cultivars in cabbage and Chinese cabbage were released by a Japanese seed company using a self-incompatibility system in 1950, many F1 hybrids of various Brassica vegetables have been developed by the same breeding methodology. Although the use of self-incompatibility has a problem of a contamination of selfed seeds in the F1 seeds due to instability of self-incompatibility, many seed companies still adopt self-incompatibility because of their higher yield of the F1 hybrid seeds than the use of the male sterility. more...

Characterization of a novel and valuable CMS system in Brassicarapa. Cytoplasmic male sterility (CMS) is extensively used to produce F1 hybrid seeds in a variety of crops. However, it has not been successfully used in Chinese cabbage (Brassicarapa L. ssp. pekinensis) because of degeneration or temperature sensitivity. Here, we characterize a novel CMS system, BVRC-CMS96, which originated in B.napus cybrid obtained from INRAE, France and transferred by us to B.rapa. Floral morphology and agronomic characteristics indicate that BVRC-CMS96 plants are 100% male sterile and show no degeneration in the BC7 generation, confirming its suitability for commercial use. We also sequenced the BVRC-CMS96 and maintainer line 18BCM mitochondrial genomes. Genomic analyses showed the presence of syntenic blocks and distinct structures between BVRC-CMS96 and 18BCM and the other known CMS systems. We found that BVRC-CMS96 has one orf222 from ‘Nap’-type CMS and two copies of orf138 from ‘Ogu’-type CMS. We analyzed expression of orf222, orf138, orf261b, and the mitochondrial energy genes (atp6, atp9, and cox1) in flower bud developmental stages S1-S5 and in four floral organs. orf138 and orf222 were both highly expressed in S4, S5-stage buds, calyx, and the stamen. RNA-seq identified differentially expressed mRNAs and lncRNAs (long non-coding RNAs) that were significantly enriched in pollen wall assembly, pollen development, and pollen coat. Our findings suggest that an energy supply disorder caused by orf222/orf138/orf261b may inhibit a series of nuclear pollen development-related genes. Our study shows that BVRC-CMS96 is a valuable CMS system, and our detailed molecular analysis will facilitate its application in Chinese cabbage breeding. more...

A cytoplasmic male sterility (CMS) system is one of the most efficient ways to produce F1 hybrid seeds in pepper (Capsicum annuum). Restorer-of-fertility (Rf) genes are a critical component within the CMS/Rf system. The inheritance of Rf genes in pepper by joint segregation analysis was examined. The inheritance of Rf genes in the two progenies was controlled by two major additive-dominant epistatic genes and additive-dominant epistasis polygene. The two major genes had high additive effects and dominant effects. In addition, there existed significant epistatic effects between the two major genes. The major genes had high heritability in F2, BC1, and BC2 generations. Also, the fertility restorer characteristic can be selected during early generations of the breeding cycle. more...

Cytoplasmic male-sterility (CMS) has been exclusively used to produce F1 hybrid seeds of onion (Allium cepa L.). A single nuclear locus, Ms, is known to restore male-fertility of CMS in onions. Unstable male-sterile onions producing a small amount of pollen grains have been identified in a previous study. When such unstable male-sterile onions were crossed with stable male-sterile onions containing CMS-T cytoplasm, male-fertility was completely restored, although genotypes of the Ms locus were homozygous recessive. Inheritance patterns indicated that male-fertility restoration was controlled by a single locus designated as Ms2. A combined approach of bulked segregant analysis and RNA-seq was used to identify candidate genes for the Ms2 locus. High resolution melting (HRM) markers were developed based on single nucleotide polymorphisms (SNPs) detected by RNA-Seq. Comparative mapping of the Ms2 locus showed that Ms2 was positioned at the end of chromosome 2 with a distance of approximately 70 cM away from the Ms locus. Although 38 contigs containing reliable SNPs were analyzed using recombinants selected from 1,344 individuals, no contig showed perfect linkage to Ms2. Interestingly, transcription levels of orf725, a CMS-associated gene in onions, were significantly reduced in male-fertile individuals of segregating populations. However, no significant change in its transcription level was observed in individuals of a segregating population with male-fertility phenotypes determined by the Ms locus, suggesting that male-fertility restoration mechanism of Ms2 might be different from that of the Ms locus. more...

Plant mitochondrial genomes sometimes carry cytoplasmic male sterility (CMS)-associated genes. These genes have been harnessed in agriculture to produce high-yielding F1 hybrid seeds in various crops. The gene orf352 was reported to be an RT102-type CMS gene in rice (Oryza sativa), although a causal demonstration of its role in CMS is lacking. Here, we employed mitochondrion-targeted transcription activator-like effector nucleases (mitoTALENs), to knock out orf352 from the mitochondrial genome in the cytoplasmic male sterile rice RT102A. We isolated 18 independent transformation events in RT102A that resulted in genome editing of orf352, including its complete removal from the mitochondrial genome in several plants. Sequence analysis around the mitoTALEN target sites revealed the repair of their induced double-strand breaks via homologous recombination. Near the 5ʹ target site, repair involved sequences identical to orf284, while repair of the 3ʹ target site yielded various new sequences that generated new chimeric genes consisting orf352 fragments. Plants with a new mitochondrial gene encoding amino acids 179 to 352 of ORF352 exhibited the same shrunken pollen grain phenotype as RT102A, whereas plants either lacking orf352 or harboring a new gene encoding amino acids 211 to 352 of ORF352 showed partial rescue of pollen viability and germination, although they failed to set seed. These results demonstrated that disruption of orf352 partially restored pollen development, indicating that amino acids 179 to 210 from ORF352 may contribute to the establishment of pollen abortion. more...

Plant mitochondrial genomes sometimes carry cytoplasmic male sterility (CMS)-associated genes. These genes have been harnessed in various crops to produce high-yielding F1 hybrid seeds. The gene open reading frame 352 (orf352) was reported to be an RT102-type CMS gene in rice (Oryza sativa), although the mechanism underlying its role in CMS is unknown. Here, we employed mitochondrion-targeted transcription activator-like effector nucleases (mitoTALENs) to knockout orf352 from the mitochondrial genome in the CMS rice RT102A. We isolated 18 independent transformation events in RT102A that resulted in genome editing of orf352, including its complete removal from the mitochondrial genome in several plants. Sequence analysis around the mitoTALEN target sites revealed their induced double-strand breaks were repaired via homologous recombination. Near the 5ʹ-target site, repair involved sequences identical to orf284, while repair of the 3ʹ-target site yielded various new sequences that generated chimeric genes consisting of orf352 fragments. Plants with a chimeric mitochondrial gene encoding amino acids 179–352 of ORF352 exhibited the same shrunken pollen grain phenotype as RT102A, whereas plants either lacking orf352 or harboring a chimeric gene encoding amino acids 211–352 of ORF352 exhibited partial rescue of pollen viability and germination, although these plants failed to set seed. These results demonstrated that disruption of orf352 partially restored pollen development, indicating that amino acids 179–210 from ORF352 may contribute to pollen abortion. more...

Maize (Zea mays) starch is an important agricultural commodity that serves as food, feed, and a raw material for industrial purposes. It is organized into starch granules (SG) inside amyloplasts and is highly accumulated in endosperms. Maize hybrids, which exhibits heterosis over their parents, are globally grown due to higher vigor of the F1 plants. However, the parental effect on the size of SG in F1 hybrid seeds remains unclear. Here we compared the seed SG sizes among two parental inbred lines (Chang7-2 and Zheng58) as well as their reciprocal hybrids. SG was observed in situ and in vitro with SEM. The size of seed SG in hybrids was more like that of female parents, especially for large SG population. Thus, the control of SG size exhibits a maternal inheritance trend in the context of plastid (amyloplast) inheritance. Our results provide some insight on selecting parental inbred lines for breeding maize hybrids with different SG sizes. more...

Chinese cabbage (Brassica rapa L. var. pekinensis) is an economically important vegetable providing nutrients such as fiber, calcium and vitamins. Most cultivars of Chinese cabbage are F1 hybrids with vegetative heterosis, and harvesting of commercial F1 hybrid seeds makes use of self-incompatibility or cytoplasmic male sterility. Production of Chinese cabbage is always threatened by abiotic and biotic stress; climate change and increasing numbers of races and varieties of pathogens are also serious problems. The demand for abiotic or biotic resistant cultivars is growing year by year. An effective breeding method is desired, and marker-assisted selection (MAS) is a leading candidate. To apply MAS, identification of the causative gene or the locus linked to the causative gene controlling a trait for breeding is required. We review the recent research using molecular biology approaches and discuss how this information can apply to Chinese cabbage breeding. more...

Background Cytoplasmic male sterility (CMS) has been widely used for commercial F1 hybrid seeds production. CMS is primarily caused by chimeric genes in mitochondrial genomes. However, which specific stages of anther development in cabbage are affected by the chimeric genes remain unclear. Results In the present study, the complete mitochondrial genomes were sequenced and assembled for the maintainer and Ogura CMS cabbage lines. The genome size of the maintainer and Ogura CMS cabbage are 219,962 bp and 236,648 bp, respectively. There are 67 and 69 unknown function ORFs identified in the maintainer and Ogura CMS cabbage mitochondrial genomes, respectively. Four orfs, orf102a, orf122b, orf138a and orf154a were specifically identified in the Ogura CMS mitochondrial genome, which were likely generated by recombination with Ogura type radish during breeding process. Among them, ORF138a and ORF154a possessed a transmembrane structure, and orf138a was co-transcribed with the atp8 and trnfM genes. orf154a is partially homologous to the ATP synthase subunit 1 (atpA) gene. Both these genes were likely responsible for the CMS phenotype. In addition, cytological sections showed that the abnormal proliferation of tapetal cells might be the immediate cause of cytoplasmic male-sterility in Ogura CMS cabbage lines. RNA-seq results showed that orf138a and orf154a in Ogura CMS might influence transcript levels of genes in energy metabolic pathways. Conclusions The presence of orf138a and orf154a lead to increased of ATPase activity and ATP content by affecting the transcript levels of genes in energy metabolic pathways, which could provide more energy for the abnormal proliferation of tapetal cells. Our data provides new insights into cytoplasmic male-sterility from whole mitochondrial genomes, cytology of anther development and transcriptome data. more...

'Yotsuboshi', a seed propagating type F1 hybrid strawberry cultivar adaptable for year-round production, was developed from the collaborative breeding program including four institutes of Mie, Kagawa and Chiba prefectures and National Agriculture and Food Research Organization (NARO) in Japan. The behavior of flower initiation is quite unique. 'otuboshi' exhibits stable extra earliness under natural condition with a lower temperature and shorter day-length, while it possesses the ever-bearing gene which results in the induction of flower initiation under long-day condition. Thus 'Yotsuboshi' is adaptable for year-round production including both forcing culture in autumn to spring and summer-autumn cultivation across Japan. 'Yotsuboshi' has several attractive traits such as a clear red fruit color, excellent fruit shape and size, high yielding ability, and superior taste with a high content of sugar and moderate acidity. The practical production system of F1 hybrid seeds and the DNA marker system for certifying the uniformity of seeds have already been established. The seeds and/or plug tray seedlings will be commercially provided from this summer for the member of the 'Research society for seed propagating type strawberries in Japan'. more...

Breeding work carried out during the period 1971–85 by the Coffee Research Institute, Ruiru, Kenya resulted in the release of a new improved hybrid Coffea arabica named Ruiru 11. The cultivar combines resistance to coffee berry disease (CBD) and leaf rust, with high yield and good cup quality attributes. The propagation by F1 hybrid seeds production, cuttings, and tip grafting do not produce enough planting materials. There was a need to explore alternative methods and tissue culture offers potential options. The objective of the study was to evaluate the effect of explant sources and cytokinins on induction and regeneration of somatic embryos. Eight different explants were cultured on half-strength Murashige and Skoog (MS) medium supplemented with 10 µm benzylaminopurine (BAP). The effect of kinetin, N6-(2-isopentyl) adenine (2iP) evaluated at (0, 0.5, 5, or 25 µm) or thidiazuron (TDZ) (0, 0.5, 1.0, or 5 µm) added in separate experiments was also evaluated. The percentage of embryogenic cultures and the numbers of embryos per explant were determined after 3 months’ culture. The explant type had a significant effect (P > 0.05) on the induction of somatic embryos. Explants from in vitro-germinated seedlings produced the highest embryogenic cultures (90%) and the highest mean number of embryos (19.36) per explant. Cytokinins strongly enhanced induction and regeneration of somatic embryos. TDZ at 1 µm produced the highest embryogenic cultures (100%) and the highest mean number of embryos (24.2). The embryos were germinated on half-strength MS medium without any hormones. A high (98%) survival rate of the regenerated plantlets was recorded over all the treatments in the greenhouse. This is the first report on induction of high-frequency direct somatic embryos from coffee juvenile tissues. This is of great significance in tissue culture and indeed molecular biology manipulations because it allows regeneration of coffee from several explants. more...

Genic male sterility (GMS) is a very important approach of heterosis exploitation in sesame (Sesamum indicum L.). Visible marker-trait linked to GMS is necessary since it can facilitate the breeding of new GMS lines and the production of F1 hybrid seeds. We have successfully developed such a GMS line showing wrinkled-leaf (JQA) from a mutant identified in a multiple-cross population in sesame. However, the underlying genetic basis for this JQA line is unclear. To understand the inheritance patterns, near-isogenic line (NIL) together with F2 and BC1 populations segregating for both pollen-fertility and leaf-shape was constructed. Morphology investigation indicated that the JQA line was controlled by a single recessive gene, Sims5. By combining bulk-segregant analysis and next-generation sequencing technology (BSA-Seq) in the NIL population, seven and four chromosome regions putatively associated with traits variation were identified by SNP and InDel markers, respectively. A 1,817.6-kb consensus region on chromosome 12 was obtained by intersecting these intervals, which was most likely the target region containing the candidate gene(s) responsible for pollen-fertility and leaf-shape. The consensus region was further narrowed down to only 219.7 kb by fine mapping in a BC1 population using SSR and InDel markers. Real-Time qRT-PCR analysis of genes within this region showed that four (XM_011097706.2, XM_011097714.2, XM_020698411.1 and XM_011097719.2) and one (XM_020698321.1) genes were highly suppressed in the anther and leaf of mutant plant, respectively, suggesting their important role in pollen and leaf development. These findings not only lay a solid foundation for the isolation and functional analysis of genes for pollen-fertility and wrinkled-leaf but also provided valuable genetic resources and molecular markers for the breeding of new sesame hybrid varieties. more...

The performance of first‐generation hybrids determines to a large extent the long‐term outcome of hybridization in natural populations. F1 hybrids can facilitate further gene flow between the two parental species, especially in animal‐pollinated flowering plants. We studied the performance of reciprocal F1 hybrids between Rhinanthus minor and R. major, two hemiparasitic, annual, self‐compatible plant species, from seed germination to seed production under controlled conditions and in the field. We sowed seeds with known ancestry outdoors before winter and followed the complete life cycle until plant death in July the following season. Germination under laboratory conditions was much lower for the F1 hybrid formed on R. major compared with the reciprocal hybrid formed on R. minor, and this confirmed previous results from similar experiments. However, this difference was not found under field conditions, which seems to indicate that the experimental conditions used for germination in the laboratory are not representative for the germination behaviour of the hybrids under more natural conditions. The earlier interpretation that F1 hybrid seeds formed on R. major face intrinsic genetic incompatibilities therefore appears to be incorrect. Both F1 hybrids performed at least as well as and sometimes better than R. minor, which had a higher fitness than R. major in one of the two years in the greenhouse and in the field transplant experiment. The high fitness of the F1 hybrids confirms findings from naturally mixed populations, where F1 hybrids appear in the first year after the two species meet, which leads to extensive advanced‐hybrid formation and introgression in subsequent generations. more...

Background The mitochondrial genomes of higher plants vary remarkably in size, structure and sequence content, as demonstrated by the accumulation and activity of repetitive DNA sequences. Incompatibility between mitochondrial genome and nuclear genome leads to non-functional male reproductive organs and results in cytoplasmic male sterility (CMS). CMS has been used to produce F1 hybrid seeds in a variety of plant species. Results Here we compared the mitochondrial genomes (mitogenomes) of Gossypium hirsutum sterile male lines CMS-2074A and CMS-2074S, as well as their restorer and maintainer lines. First, we noticed the mitogenome organization and sequences were conserved in these lines. Second, we discovered the mitogenomes of 2074A and 2074S underwent large-scale substitutions and rearrangements. Actually, there were five and six unique chimeric open reading frames (ORFs) in 2074A and 2074S, respectively, which were derived from the recombination between unique repetitive sequences and nearby functional genes. Third, we found out four chimeric ORFs that were differentially transcribed in sterile line (2074A) and fertile-restored line. Conclusions These four novel and recombinant ORFs are potential candidates that confer CMS character in 2074A. In addition, our observations suggest that CMS in cotton is associated with the accelerated rates of rearrangement, and that novel expression products are derived from recombinant ORFs. Electronic supplementary material The online version of this article (10.1186/s12864-018-5122-y) contains supplementary material, which is available to authorized users. more...

Cytoplasmic male sterility (CMS) is an important trait in the production of F1 hybrid seed of chili peppers. The creation and detection of CMS and maintainer lines by conventional methods require a lot of time and effort, and the accuracy is influenced by many factors. Therefore, the application of molecular markers is necessary to increase the efficiency of breeding. In this research, we investigated the specificity of four primer sets, coxIISCAR, atp6SCAR, RfSCAR and coxTri-M1 related to CMS trait in different lines of Chi Thien cultivar that is planted widely in Vietnam. The results showed that three of the four sets of primers (coxIISCAR, RfSCAR and coxTri-M1) could discriminate exactly the CMS and the maintainer lines, the two most important lines for the production of F1 hybrid seeds. These results showed the feasibility of the application of these primer sets to increase the effectiveness of the chili peppers breeding process in Vietnam. more...

DNA markers are powerful tools for molecular breeding or checking the genetic homogeneity of F1 hybrid seeds. For the simple and fast approach to detect DNA polymorphisms, simple sequence repeats (SSRs), which are tandem repeats of short sequence motifs (mainly 1–6 bases), are powerful markers because of their codominant mode of inheritance, higher reliability, and abundance in genomes. In Allium, GT/CA repeats are abundant than GA/CT repeats, and AAG/CTT motif is the most frequent in the trinucleotide SSRs. NGS technologies including public sequence data will be a mainstream for identifying new SSR markers. more...

To assess the dormancy associated weedy risk of the F1 hybrid generated by hybridization between Brassica juncea (maternal) and Brassica napus (paternal), seed germination, dormancy and longevity were examined sequentially after seed harvest. The F1 hybrids exhibited the intermediate characteristics of their parents in seed germination and dormancy with relatively high dormancy rate of 41.1%. In summer, F1 hybrid seeds buried in the 3 cm soil exhibited greater viability (52.4%) than those in the soil surface with greater seed longevity (74.6%) than its maternal (63.3%) and paternal (33.7%) parents at 100 days of over-summering in soil. In winter, F1 seeds buried in the soil surface were more viable than those in the 3 cm soil with greater seed longevity (83.5%) than its maternal (39.0%) and paternal (71.7%) parents at 100 days of over-wintering in soil. Therefore, it is concluded that F1 hybrid resulted from gene flow from OSR to mustard has high seed dormancy and longevity during summer and winter, suggesting its weedy risk potential. Further studies are required to examine the reproductivity and fitness cost of F1 hybrid to make a clearer conclusion of its weedy risk. more...

Genic male sterility conditioned by either photoperiod (PGMS) or temperature (TGMS) is the key trait that has enabled the establishment of the two-line hybrid rice (Oryza sativa L.) system. The PGMS trait is known to result from a C→G mutation in a long noncoding RNA gene (lncR) and the TGMS from a premature stop codon mutation (TC/GC→TA) in an RNase Z gene (RNZ). To develop an efficient genotyping method capable of distinguishing all potential genotypes for the loci of lncR and RNZ, the present study explored the capacity of four approaches in high-resolution melting (HRM) curve analysis, viz. amplicon scanning, amplicon scanning with pre-PCR addition of mutant DNA template or inclusion of an unlabeled oligonucleotide probe, and melting analysis by competitive amplification of differentially melting amplicons (CADMA). The former three approaches were demonstrated to be able to differentiate only a few genotypes; in contrast, CADMA was shown to be able to discriminate all possible genotypes of both genes. For the lncR locus, HRM curves of three possible genotypes (PGMS, wild-type line and their hybrid) had peak fluorescence differences (ΔFs) of ~0.075 to ~0.20, significantly greater than the threshold (>0.05) for differentiation. For the RNZ locus, the five genotypes that would be of interest to breeders and seed technologists were separated according their HRM curves with ΔFs > ~0.1 between any two genotypes. The usefulness of the CADMA-based approach was further validated by analyzing a number of uncharacterized genotypes including P/TGMS lines, F1 hybrid seeds and F2 plants derived from crosses of P/TGMS lines with wild-type lines. Taken together, the present study proved the usefulness of CADMA in plant genotyping and established a CADMA-based HRM analysis method for high-throughput P/TGMS genotyping, which can be applied not only to marker-assisted selection of PGMS and TGMS rice but also to seed purity testing in the two-line hybrid rice system. more...

Genomic imprinting often results in parent-of-origin specific differential expression of maternally and paternally inherited alleles. In plants, the triploid endosperm is where gene imprinting occurs most often, but aside from studies on Arabidopsis, little is known about gene imprinting in dicotyledons. In this study, we inspected genomic imprinting in castor bean (Ricinus communis) endosperm, which persists throughout seed development. After mapping out the polymorphic SNP loci between accessions ZB306 and ZB107, we generated deep sequencing RNA profiles of F1 hybrid seeds derived from reciprocal crosses. Using polymorphic SNP sites to quantify allele-specific expression levels, we identified 209 genes in reciprocal endosperms with potential parent-of-origin specific expression, including 200 maternally expressed genes and 9 paternally expressed genes. In total, 57 of the imprinted genes were validated via reverse transcriptase-polymerase chain reaction sequencing, and analysis of the genomic DNA methylation distribution between embryo and endosperm tissues showed significant hypomethylation in the endosperm and an enrichment of differentially methylated regions around the identified genes. Curiously, the expression of the imprinted genes was not tightly linked to DNA methylation. These results largely extended gene imprinting information existing in plants, providing potential directions for further research in gene imprinting. more...

Papaya (Carica papaya) is an important economic fruit crop in the tropical and subtropics. The world production of papaya in 2008 was over 9.1 million metric tons in 20 countries. Thailand ranged eighth, while India was first in the production of papaya followed by Brazil, Indonesia, Nigeria, Mexico, Ethiopia and others. In Thailand papaya is one of the most important fruit crops. The total cultivation area in Thailand covered about 17,430 ha. The eastern and the southern regions have the largest papaya area of 44 and 16%, respectively, in 2008, with an overall production volume of just over 201,099 t. The overall quantity of product exported in 2008 was about 3,458 t worth around Baht 111.89 mil. One of the main problems of papaya cultivation and the most ubiquitous and widespread is the Papaya ring spot virus (PRSV). The occurrence of PRSV disease was first observed in 1975 in the northeastern region has spread all over the country today. The Department of Agriculture (DOA), Ministry of Agriculture and Cooperatives have conducted papaya breeding since 1984. These programs were divided into two types, conventional breeding and genetic engineering. Conventional breeding included collection, selection and crossing of papayas. Papaya cultivars were collected from various sources, planted and selected for agricultural characteristics. They were self-pollinated to increase the purity of the lines. The DOA accepted and approved ‘Khaek Dam Si Sa Ket’ as a new cultivar in 1994. With regard to cross breeding, ‘Khaek Dam’ was crossed with ‘Coimbatire No. 2’ (CO2) cultivar. The cross breeding can be selected from the F1 hybrid papaya. The DOA approved this cultivar ‘Phichit’ in 1997. There is also a cross between the ‘Khaek Dam’ cultivar and the ‘Florida Tolerant’ cultivar. There were large amounts of F1 hybrid seeds which were grown, selected and self-pollinated for an inbred line. From this program, new cultivars, ‘Khaek Dam Tha Phra’ and ‘Khon Kaen 80’ were selected based on good agricultural traits and then they were approved in 1997 and 2010, respectively. Genetic engineering improvement under the DOA was in collaboration with Cornell University. The coat protein gene (CP gene) of PRSV was transferred into Thai papaya, ‘Khaek Dam’ and ‘Khaek Nuan’ cultivars. Potential resistant cultivars were selected for the R0 PRSV resistance, including one ‘Khaek Dam’ and four ‘Khaek Nuan’. Currently, one cultivar ‘Khaek Dam’ (R3 300KD) and two ‘Khaek Nuan’ (R3 319-1KN-180 and R3 319-1KN-181) cultivars were selected for the R3 PRSV resistance. more...

Wide crossing is a useful method for transferring traits of interest from wild Triticeae species to wheat. In this study, Aegilops sharonensis was successfully hybridized to three tetraploid wheat species with crossability varying from 0.86 to 1.76 %. F1 hybrids were verified by their display of intermediate characteristics in morphology, cytology, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis profiles. The exogenous x- and y-type subunits of high-molecular-weight glutenin subunits of Ae. sharonensis were expressed in F1 hybrid seeds and showed identical electrophoretic mobilities to those originally present in Ae. sharonensis. In F2 hybrids, the x-type subunit migrated faster, indicating that a decrease in molecular mass had occurred. Cloning of the open reading frames of subunit variants revealed that the x-type subunit had protein sequence variations, including single residue mutations, and insertions and deletions involving one or more repeat motifs. The two deletions causing the size reduction of the exogenous x-subunits of Ae. sharonensis in the F2 seeds were most likely the result of slip-mismatching. more...

For the maping of Cassava mosaic disease (CMD) resistance gene, CO2 and MNga-1 parents were used for hybridization to develop F1 hybrid seeds and 153 progenies were planted in the field for genotyping. Out of the 75 SSR primers used for parental polymorphism, 57 produced polymorphic bands between parents and these were used to screen the 153 progenies of the cross for genotyping. Out of these 57 SSR primer pairs SSRY32, SSRY36, SSRY83, SSRY339, NS149 and NS890 loci produced single marker which clearly distinguished the parents. Based on the said six primers, 12 progenies out of 153 were identified as self pollinated seeds of CO2 female parent. So these types of SSR markers were very much useful for identification of true hybrid seedlings in the early stage of growth and genotyping of the progenies more accurately for gene mapping. DOI: http://dx.doi.org/10.3329/bjb.v42i1.15906 Bangladesh J. Bot. 42(1): 155-159, 2013 (June) more...

Aim. Dynamics and synchronism of florescence of winter rape sterile and fertile forms were studied to obtain high-quality stock seeds of F1.hybrids.Material. Lines of Ogu-inra, Polima sterility types and eight fertile forms were studied. It was found that three periods could be distinguished in provision of sterile forms with pollen.Results. In the first period of florescence from the third ten-day interval of April to the third ten-day interval of May sufficient amount of pollen is produced. Over this period 89 % of floriferous fertile flowers accrue to 68.5 % of sterile flowers. It was revealed that at the end of florescence (the third ten-day interval of June) of sterile forms there was no pollen of fertile forms. Around 6 % of sterile flowers bear blossom during this period.Conclusions. In the production of F1 hybrid seeds the first period of florescence of sterile forms ensures obtainment of high-quality stock seeds, and biological contamination can be observed during the second and third periods. Recommendations regarding further investigation of paternal forms to improve winter rape F1 hybrid seed industry are given. more...

Polyploids are a potentially important germplasm source in seedless citrus breeding program. Seedlessness is one of the most promising traits of commercial mandarin breeds that mandarin triploid hybrids possess permanently. The formation of new constant triploid hybrids can be recovered through diploid species hybridization from the fusion of divalent gametes at low frequencyor intra-and inter-ploidy crosses. However, extensive breeding work based on small F1 hybrid seeds developed is impossible without a very effective aseptic methodology and ploidy event. In this study, in vitro embryo culture was employed to recover natural hybrids from monoembryonic diploid, open-pollinated mandarin. Flow cytometry was used to determine ploidy level. A total of 10,289 seeds were extracted from 792 fruits having approximately 13 seeds per fruit. Average frequency of small seeds developed was 7.1%, while the average frequency of small seeds per fruit were: 8.9% for ‘Clementine’ 10.2% for ‘Harehime’ 2.6% for ‘Kamja’ 3.1% for ‘Pyunkyool’ 2.8% for ‘Sadookam’ and 7.0% for ‘Wilking’ mandarin. Average size of a perfect seed was 49.52±0.07 mm2 (‘Clementine’) while the small seed measured 7.95±0.04 mm2 (‘Clementine’), which was about 1/6 smaller than the perfect seed. In total, 731 small seeds were obtained and all of them contained only one embryo per seed. The efficiency of ‘Clementine’ was 14 times higher than ‘Wilking’ and more than 109 times higher than ‘Pyunkyool’. The basic information on spontaneous polyploidy provides for the hybridization of constant triploids and increases the efficiency of conventional cross. more...

In F1 hybrid breeding of Brassica vegetables utilizing the self-incompatibility system, identification of S genotypes in breeding lines is required. In the present study, we developed S-tester lines of 87 S haplotypes, i.e., 42 S haplotypes in B. rapa and 45 S haplotypes in B. oleracea. With these materials, we established a simple, efficient, and reliable dot-blot technique for S genotyping for 40 S haplotypes of B. rapa and and 33 of B. oleracea using allele-specific oligonucleotide probes and allele-specific primer pairs designed from sequences of each SP11 allele. In this method, DNA fragments amplified using multiplex primer pairs with digoxigenin-dUTP were hybridized with dot-blotted allele-specific oligonucleotide probes with distinct signals. In addition, we developed a screening method for identification of plants harboring a particular S haplotype using a labeled allele-specific oligonucleotide probe. This method is considered to be useful for purity testing of F1 hybrid seeds. more...

High oil content is one of the most important characteristics of rapeseed (Brassica napus L.) breeding. In order to understand the genetic basis of seed oil content, a series of reciprocal crosses between rapeseed parents with high oil content (53110, 61616 and 6F313), medium-oil content (Zhongshuang 9) and low oil content (51070 and 93275) were conducted. It was found that the oil content of F1 hybrid seeds in rapeseed was mainly controlled by the maternal genotype. The maternal effect value of oil content was estimated to be 0.86. The pollen parent had a xenia effect on oil content, estimated to be 0.14 which changed the mean value by 1.86 percent. The inheritance of oil content was studied in a set of 8 × 8 diallel crosses of different varieties. The results indicated that the inheritance of oil content could be explained by an additive-dominant-epistasis model. Although the dominant and additive effects played major roles and accounted for more than 70% of the total variance, there was also a small epistatic effect. The broad and narrow sense heritability of oil content was 83.88 and 36.94%, respectively. Based on the oil content differences between the reciprocal crosses in the same offspring generation (F1 and F2) in rapeseed, it could be concluded that there were significant cytoplasmic effects on oil content. In this study, two lines with significantly cytoplasmic effects, either positive or negative, were selected. more...

Cytoplasmic male sterility (CMS)/restorer-of-fertility (Rf) is an economical and efficient system to produce F1 hybrid seeds. Although the CMS/Rf system has been used to produce hybrid seeds of hot peppers, this system has never been used for sweet pepper seed production, presumably due to the inability to select stable restorer lines during the breeding process. To test the feasibility of the CMS/Rf system in sweet pepper breeding, we investigated the distribution of haplotypes of previously developed, CMS-associated markers (orf456, ψ atp6-2, CRF-SCAR, OPP13-CAPS, PR-CAPS, and PR-SNP) in 27 commercial sweet pepper F1 hybrids and 12 breeding lines. When CMS-associated cytoplasmic markers orf456 and ψ atp6-2 were applied, male sterile cytoplasm was not detected in commercial sweet pepper cultivars. When nuclear haplotype markers linked to Rf were applied, all sweet pepper cultivars showed haplotype 3, haplotype 1, and the rf genotype for OPP13-CAPS, PR-CAPS, and CRF-SCAR, respectively. In contrast, we were able to detect male sterile cytoplasm in some breeding lines, and we were also able to detect polymorphisms for PR-CAPS between stable and unstable maintainer lines. The 17T7-SNP also showed polymorphisms between unstable and stable maintainer (or restorer) lines. In conclusion, we expect that it will be possible to develop stable A, B, and C sweet pepper lines using CMS-associated markers and that this will eventually lead to successful implementation of the CMS/Rf system to produce F1 hybrid sweet pepper seeds. more...

Hybrid cauliflowers have been developed to exploit heterosis and to improve uniformity of production. Two breeding systems are commonly employed, self-incompatibility (SI) and cytoplasmic male sterility (CMS). Sibs, assumed to be self-inbred, often contaminate hybrid seed lots in the SI system and whilst self-inbreeding is not possible in the CMS system, plants that look like sibs occur. The objective of this study was to develop microsatellite markers for male and female cauliflower parent lines of both SI and CMS systems and to use them to screen sibs and aberrant plants in F1 hybrids. Fifty six pairs of microsatellite primers were screened and 8 primer pairs produced co-dominant markers in parent plants and two pairs of markers were chosen for purity testing of F1 hybrid seeds. Controlled pollinations were conducted in the glasshouse to produce hybrid and selfed-seeds. These seeds were grown in a field trial to identify morphologically normal and sib plants and to assess the reliability of microsatellite markers in detecting sib plants. Microsatellite analysis of morphological sib plants from the SI system revealed that these were not always self-inbred, in contrast, most self-inbred plants showed normal growth. Similarly, all morphological sibs from the CMS system showed hybrid bands. This suggests that morphological sibs were not always due to selfing but possibly to an interaction between genetic and environmental factors and this requires further investigation. more...

The objective of this study was to determine the genetic relationships among four types (A, B, C and D) of Panicum coloratum L. on the basis of the crossability and the amplified fragment length polymorphism (AFLP) variations among the types, and the meiotic chromosome pairing and fertility in F1 hybrids obtained from crosses between different types. F1 hybrids were obtained from crosses between P. coloratum L. var. makarikariense cv. Burnett (A) and P. coloratum L. PI 404632 (D), and between P. coloratum L. CPI 16794 (B) and P. coloratum L. cv. Solai (C). Other crosses failed to produce F1 hybrid seeds. F1 hybrids between Burnett (A) and PI 404632 (D) had 2n = 36 chromosomes and regular meiotic chromosome pairing with 18 bivalents per cell. They produced approximately 80% stainable pollen and normally set seeds. F1 hybrids between Solai (C) and CPI 16794 (B) had 2n = 45 chromosomes and a mean chromosome pairing of 9.50 univalents, 17.67 bivalents and 0.05 trivalents. The most frequent paring behavior was nine univalents and 18 bivalents, suggesting that Solai has two genomes homologous to those of CPI 16794 and one different genome. The F1 hybrids showed approximately 80% stainable pollen and approximately 20% seed fertility. Cluster analysis of polymorphic AFLP in five plants of each of the four types yielded two major clusters. Burnett (A) and PI 404632 (D) clustered together, while Solai (C) clustered with CPI 16794 (B). The results of hybridization studies and AFLP analysis of the four types of P. coloratum, and meiotic examination of the derived F1 hybrids demonstrate that types A and D are genetically differentiated from types B and C, and are reproductively isolated from these two types. more...

DNA markers are powerful tools for verifying the varietal identity and genetic homogeneity of F1 hybrid seeds. F1 varieties are becoming increasingly prevalent in bunching onion (Allium fistulosum L.) production in Japan because of the high uniformity of agronomic traits. However, bunching onion is an allogamous crop and suffers from severe inbreeding depression when selfed. It is considered that not only open-pollinated varieties but also the parental lines of F1 hybrids should maintain a certain degree of average heterozygosity and hence genetic heterogeneity. In the present study, the genetic homogeneity of eight bunching onion varieties, including six F1 hybrids, was evaluated using 14 SSR markers. Two or more polymorphic alleles were detected at all of the SSR loci examined in each variety. The number of alleles detected in the eight varieties ranged from 3 to 7 among the 14 SSR loci, and the polymorphism information content from 0.41 to 0.76. All the varieties examined displayed very low degrees of uniformity at all of these polymorphic loci. Based on these results, it may be impossible to determine an appropriate genotypic identity for any of the existing bunching onion varieties. To facilitate and enhance the accuracy of variety identification, we proposed here an “SSR-tagged breeding” scheme in which the plants homozygous at a few SSR loci would be selected out of a foundation seed field. This scheme may enable to achieve efficient variety identification and purity determination of F1 seeds not only in bunching onion but also in any allogamous crops exhibiting severe inbreeding depression. more...

Ergot or sugary disease of sorghum has become an important constraint in North and South American countries that rely on F1 hybrid seeds for high productivity. The objective of this research was to determine the vulnerability of various germplasm sources and publicly bred sorghum lines to sugary disease (Claviceps africana) in the United States. Flower characteristics associated with sugary disease resistance were also studied. A-/B-line pairs, R-lines, putative sources of resistance and their hybrid combinations with an A3 cytoplasmic male-sterile source were evaluated using a disease incidence, severity, and dual-ranking system. Trials were planted in a randomized complete block design with three replications and repeated in at least two planting dates. Planting dates and pedigrees had significant effects on overall ranking for resistance. A-lines were most susceptible to sugary disease. R-lines were more susceptible than B-lines with respect to incidence and severity of the disease. Newer releases of A- and B-lines were more susceptible to sugary disease than older releases. Sugary disease reaction of A-lines was a good indicator of disease reaction of B-lines. Tx2737, a popular R-line, was highly susceptible to sugary disease in spite of being a good pollen shedder because the stigma emerged from glumes 2±3 days before anthesis. The combination of flower characteristics associated with resistance were least exposure time of stigma to inoculum before pollination, rapid stigma drying after pollination, and small stigma. An Ethiopian male-fertile germplasm accession, IS 8525, had good levels of resistance. Its A3 male-sterile hybrid had the highest level of resistance in the male-sterile background. IS 8525 should be exploited in host-plant resistance strategies. more...

Several simple methods of DNA preparation from plant tissues were evaluated for PCR-RFLP analyses of SLG and SRK alleles, which can be used for the identification of S haplotypes of breeding lines in broccoli and cabbage (Brassica oleracea L.) and in purity tests of F1 hybrid seeds. On the five methods tested, the NaI method was found to be the most suitable for the amplification of the SLG and SRK alleles. This method enables the use of a single seed as testing material. Using this method, we identified S haplotypes of 31 broccoli and 31 cabbage cultivars. Ninety-four percent of the cultivars of broccoli and 97% of those of cabbage were-single cross F1 hybrids. Nine and 15 S haplotypes were found in broccoli and cabbage, respectively. The small number of S haplotypes in broccoli suggests the importance of incorporating new S haplotypes in the breeding program. more...

Genomic imprinting is an epigenetic phenomenon leading to parent-of-origin specific differential expression of maternally and paternally inherited alleles. In plants, genomic imprinting has mainly been observed in the endosperm, an ephemeral triploid tissue derived after fertilization of the diploid central cell with a haploid sperm cell. In an effort to identify novel imprinted genes in Arabidopsis thaliana, we generated deep sequencing RNA profiles of F1 hybrid seeds derived after reciprocal crosses of Arabidopsis Col-0 and Bur-0 accessions. Using polymorphic sites to quantify allele-specific expression levels, we could identify more than 60 genes with potential parent-of-origin specific expression. By analyzing the distribution of DNA methylation and epigenetic marks established by Polycomb group (PcG) proteins using publicly available datasets, we suggest that for maternally expressed genes (MEGs) repression of the paternally inherited alleles largely depends on DNA methylation or PcG-mediated repression, whereas repression of the maternal alleles of paternally expressed genes (PEGs) predominantly depends on PcG proteins. While maternal alleles of MEGs are also targeted by PcG proteins, such targeting does not cause complete repression. Candidate MEGs and PEGs are enriched for cis-proximal transposons, suggesting that transposons might be a driving force for the evolution of imprinted genes in Arabidopsis. In addition, we find that MEGs and PEGs are significantly faster evolving when compared to other genes in the genome. In contrast to the predominant location of mammalian imprinted genes in clusters, cluster formation was only detected for few MEGs and PEGs, suggesting that clustering is not a major requirement for imprinted gene regulation in Arabidopsis., PLoS Genetics, 7 (6), ISSN:1553-7390, ISSN:1553-7404 more...

The fatty acid composition of seed-oil of breeding lines and F1 hybrids of Matthiola incana was analyzed, using direct esterification and gas chromatography. The breeding lines tested differed significantly with respect to the levels of palmitic, oleic, linoleic and linolenic acids. Embryonic-stage heterosis in linolenic acid concentration was demonstrated by F1 hybrid seeds, derived from mating horticulturally different lines of M. incana. Linolenic acid content was negatively correlated with both oleic acid content (r=−0.85) and linoleic acid content (r=−0.66). None of the breeding lines or the F1 hybrids significantly passed the limit of 67% linolenic acid. Possible genetic and biochemical explanations for the above phenotypic data are discussed. more...

Plants, when exposed to sub-lethal stress (induction stress), develop the ability to withstand severe temperatures and this phenomenon is often referred to as acquired thermotolerance. Earlier it was reported that induction stress alters gene expression and brings greater adaptation to heat stress and that the genetic variability in thermotolerance is only seen upon induction stress. Based on this concept, the temperature induction response (TIR) technique has been developed to identify thermotolerant lines. By following the TIR technique, sunflower hybrid KBSH-1 parents were screened for high temperature tolerance. Seedlings of parental lines including CMS 234 A, CMS 234 B and 6 D-1 showed considerable genetic variability for thermotolerance and it was attributed to the expression of existing residual variability for stress responses. Thus, the existing variability forms the basis for identifying thermotolerant lines. The identified parental inbred lines were selected and established in the field and crossed to get F1 hybrid seeds. The KBSH-1 hybrid developed from selected variants of parental lines was compared with the original KBSH-1 for thermotolerance. The selected KBSH-1 was more tolerant compared with the original hybrid both at the seedling as well as at the plant level. The physiological and molecular basis of thermotolerance was studied in the KBSH-1 original and the hybrid developed from selected variants of parental lines. The selected hybrid exhibited high tolerance to Menadione (naphthoquinone)-induced oxidative stress. Even the methyl viologen-induced oxidative stress damage was relatively less in the selected hybrid population. The selected hybrid also showed enhanced expression of the heat shock proteins HSP 90 and HSP 104 and also accumulated higher levels of the heat shock transcription factor HSFA. more...

Broccoli (Brassica oleracea var. italica) is a vegetable cole crop of considerable interest to breeders and seed companies since its area of production has increased in recent years mainly due to improved nutritional qualities, e.g. anticancer properties. Breeding companies strive more and more to bring F1 hybrid seeds onto the market. F1cultivars ensure high uniformity, offer high yields due to heterosis, allow rapid production and selection of desired genotypes and provide protection of plant breeder’s rights and the markets of seed companies. The production of hybrid cultivars requires homozygous parental lines. Inbred lines in broccoli can be produced by recurrent selfing, a procedure that takes time (6 to 7 generations of selfing) and is labour intensive due to sporophitic self-incompatibility. An alternative way to obtain pure inbred lines in one generation is the production of doubled haploid (DH) lines by microspore culture. This protocol can also be applied to other cole crops such as head and tronchuda cabbages using small adaptations. more...

Brassicaceae crops include oil crops, vegetables, condiments, fodder crops, and ornamental plants. Most of these crops belong to or are closely related to the genus Brassica. The Brassicaceae also includes the most intensively studied model plant, Arabidopsis thaliana. In molecular genetic studies of Brassicaceae crops, information on A. thaliana genes is highly useful, and many genes important for plant breeding have been identified. Different species of Brassica have various numbers of chromosomes. The genome relationship of three monogenomic species and three digenomic species that are well known as U’s triangle was discovered in Japan, and relationships between different genera have also been studied (Mizushima 1980). In these studies, interspecific and intergeneric hybridizations have been performed, and some interspecific and intergeneric hybrids have been used as breeding materials. Studies on interspecific and intergeneric hybridization are reviewed by Kaneko and Bang in this special issue. Genome synteny relationships between different species in Brassica and closely related genera are complicated, as exemplified by the different numbers of chromosomes between species. The monogenomic species of Brassica and closely related genera have three copies, on average, of genes homologous to each A. thaliana gene, indicating whole genome triplication in the evolution of the ancestral species of Brassica and closely related genera. The recent development of next-generation sequencers has accelerated the determination of whole genome sequences from many species. A draft sequence of the Brassica rapa genome was published in 2011 (Wang et al. 2011), and whole genome sequences of other species of Brassicaceae crops will also be published soon. The progress with genome studies of Brassicaceae crops and genome relationships between them are described by Ashutosh et al. Many Brassicaceae crops have self-incompatibility, which is not common in other seed-propagated crops. Self-incompatibility is a commonly found trait in many angiosperm species, but self-compatible plants have been selected as crops. The genetics and molecular mechanisms of self-incompatibility have been most intensively studied using Brassica species, and this trait is also used as a tool for producing F1 hybrid seeds of Brassicaceae vegetables. Recent studies on Brassica self-incompatibility are introduced by Kitashiba and Nasrallah. On the other hand, the trait most widely used for F1 hybrid seed production in many crop species is cytoplasmic male sterility. Cytoplasmic male-sterile lines can be obtained by interspecific hybridization and repeated backcrossing with a paternal species, and this form of sterility is considered to be caused by incompatibility between the cytoplasm and nucleus. Cytoplasmic male sterility in Brassicaceae crops is discussed here by Yamagishi and Bhat. Brassicaceae crops generally contain glucosinolates, which are degraded to isothiocyanates by the endogenous enzyme myrosinase after disruption of cells. Isothiocyanates are pungent compounds, probably important for defense against herbivores, and they determine the taste or quality of vegetables, condiments, and feed. These compounds are reported to have anti-carcinogenic activity; therefore, Brassica vegetables are in the spotlight for medicinal uses. Studies on glucosinolates in Brassicaceae vegetables are presented by Ishida et al. Because of water deficit in farmland, probably due to global warming, drought tolerance has become increasingly important in rapeseed breeding. Drought is frequently accompanied by salinity; therefore, recent studies on rapeseed breeding for drought and salt tolerance are reviewed by Zhang et al. Furthermore, herbicide-tolerant cultivars developed by genetic engineering are an increasing percentage of rapeseed produced around the world. For the production of these genetically modified (GM) cultivars, pollen-mediated gene flow from GM cultivars to wild plants or landraces should be limited. Recent studies on the possibility of pollen-mediated gene flow from GM cultivars of rapeseed are described by Tsuda et al. After the Great East Japan Earthquake, the Rapeseed Project for Restoring Tsunami-Salt-Damaged Farmland was started by Tohoku University because of the high tolerance of Brassica crops to salinity. This project has been supported by Kureha Corporation and other companies. The cost of publication of these reviews is partially supported by this project. more...

A natural male sterile mutant of Salvia miltiorrhiza (Labiatae, Sh-B) was found during field survey in 2002. Our objective was to analyze its genetic mechanism for producing F1 hybrid seeds and to develop a molecular marker linked to male sterile gene for selection of a hybrid parent line. The segregation ratios of male sterile plants to fertile plants in the progenies of both testcross and backcross were 1:1 in continuous experiments conducted in 2006–2009. The male sterile Sh-B was heterozygous (Msms). The male sterile plants could capture most pollen (2 granule/cm2·24 h) with row ratio (female : male 2 : 1) within 45-cm distance and harvest the largest amount of 6495 g hybrid seeds per hectare. We also developed DNA markers linked to the male sterile gene in a segregating population using bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) techniques. The segregating population was subjected to BSA-AFLP with 128 primer combinations. One out of fourteen AFLP markers (E11/M4208) was identified as tightly linked to the dominant male sterile gene with a recombination frequency of 6.85% and at a distance of 6.89 cM. This marker could be converted to PCR-based assay for large-scale selection of fertile plants in MAS (marker-assisted selection) at the seedling stage. Blastn analysis indicated that the male sterile gene sequence showed higher identity with nucleotides in Arabidopsis chromosome 1–5, and was more likely to encode S-adenosylmethionine-dependent methyltransferase, in which DNA methylation regulated the development of plant gametogenesis. more...

Restriction fragment length polymorphisms of cytoplasmic DNAs and nuclear rDNA were analyzed in several Cichorium intybus genotypes, comprising four white inbred lines, eight red witloof experimental lines, and a number of F1 hybrids derived from two white parents. Chloroplast and mitochondrial restriction patterns led to the distinction between two different cytoplasms, called I and II. Southern hybridization using a nuclear rDNA probe revealed that all the lines possessed two types of rDNA repeat units. The shortest unit was 10 kb and was common to all lines. The largest rDNA repeat unit was 10.5 kb in lines I and 10.4 kb in lines II. In addition, a sequence heterogeneity between the 10.5 and 10.4-kb rDNA repeat units was revealed by Sac I digestion. A 10-kb rDNA unit was successively cloned, mapped, and used as a probe to check the genetic purity of F1 hybrid seeds between line I and II white parents. We found a 30% average percentage of impurities, originating both from selfing and full-sib crossing, in different open-pollinated hybrid samples. more...

Electrophoretic profiles of crude protein extracts from seed of F1 hybrids and reciprocal crosses among diploid, tetraploid and hexaploid wheats were compared with those of their respective parental species. The electrophoretic patterns within each of three pairs of reciprocal crosses, T.boeoticum X T.urartu, T.monococcun X T. urartu and T.dicoccum X T. araraticum, were different from one another but were identical with those of their respective maternal parents. Protein bands characteristic of the paternal parents were missing in F1 hybrid seed suggesting that the major seed proteins in wheat were presumably regulated by genotype of the maternal parent rather than by the seed genotype. However, in another three pairs of reciprocal crosses, T.boeoticum X T. durum, T.dicoccum X T.aestivum and T. zhukovskyi x T. aestivum, protein bands attributable to the paternal parents were present in the F1 hybrid seeds indicating that the seed proteins were not always exclusively regulated by the maternal genotype. The expression of paternal genomes is presumably determined by dosage and genetic affinity of the maternal and paternal genomes in the hybrid endosperm. The maternal regulation of seed protein content is probably accomplished through the maternal control over seed size. The seed protein quality may, however, depend upon the extent of expression of the paternal genome. more...

The effect of frequency-dependent advantage in wheat was investigated by growing F1. hybrid seeds of the crosses (Warimek X Halberd) and (Wariquam x Halberd) in a stand of Halberd at 5 frequencies: 4 %, 6.25 %, 11.11 %, 25 % and 50 %. A reduction of 35 % to 40 % in grain yield of individual plants was observed with both hybrids as their frequencies changed from 4% to 50 %. A similar trend with frequency was noted for several other plant characteristics, including total grain number, particularly with those measured towards the end of the growing season. Halberd plants did not show a corresponding increase as their frequency declined from 96 % to 50%. - The following season, 76 F4 lines from the cross (Warimek X Halberd) and 70 F4 lines from (Wariquam x Gabo) were grown at frequencies of 6.25% and 18.75% in machine sown stands of Wariquam and Halberd, respectively. Again grain yield decreased as genotypic frequency increased. Furthermore, there was a positive correlation between frequency-dependent advantage and relative grain yield, suggesting that high yielding genotypes show a greater advantage at low frequencies than lower yielding ones. more...