Napus Parent Research Articles

Potential of increasing yield of spring Brassica napus canola by using Brassica rapa gene pool with emphasis on yellow sarson

Context Broadening the genetic base of canola (Brassica napus) is needed to develop improved hybrid cultivars. Wide genetic diversity is present in its parental species B. rapa and B. oleracea. In the case of B. rapa, the yellow sarson type from Asia is genetically distinct from all other types. Aims The objective of this research was to investigate the prospect of using yellow sarson to improve the performance of hybrid canola cultivars. Methods Inbred B. napus canola lines derived from an B. napus × B. rapa interspecific cross, and their F1 hybrids with the B. napus parent, as a tester, were compared on agronomic and seed quality traits; the inbreds were also evaluated for genetic diversity by using molecular markers. Key results Seed yield of the hybrids was significantly greater than the inbreds and the B. napus parent and exhibited more than 15% mid-parent heterosis (MPH). Genetic diversity did not show significant correlation with seed yield in the inbred population; however, it showed a positive correlation with MPH. Inbred yield as well as MPH showed a positive correlation with hybrid yield. For other traits, the performance of the inbreds showed a significant positive correlation with the performance of the hybrids; the average MPH for these traits was low or close to zero. Conclusions The yellow sarson gene pool showed great potential for use in the breeding of hybrid canola. Implications The knowledge gained and germplasm developed from this research can be used by breeders and researchers to develop improved canola cultivars.

Potential of the C Genome of the Different Variants of Brassica oleracea for Heterosis in Spring B. napus Canola.

The genetic base of Brassica napus canola need to be broadened for exploitation of heterosis at a greater level in the breeding of F1 hybrid canola cultivars. In this study, we evaluated 228 inbred B. napus canola lines derived from six B. napus × B. oleracea interspecific crosses and following two breeding methods (F2- and BC1-derived lines) to understand the effect of the B. oleracea alleles on heterosis for different agronomic and seed quality traits. Test hybrids of the inbreds derived from crosses involving vars. botrytis (cauliflower), alboglabra (Chinese kale) and capitata (cabbage) cv. Badger Shipper, on an average, gave about 10% mid-parent heterosis (MPH), and about 67% of the test hybrids gave higher seed yield than the common B. napus parent indicating that B. oleracea alleles can contribute to heterosis for seed yield in spring B. napus canola hybrids. This was also evident from a positive correlation of the genetic distance of the inbred lines from the common B. napus parent with MPH for seed yield (r = 0.31) as well as with hybrid yield (r = 0.26). Almost no correlation was found between genetic distance and MPH for seed oil and protein content as well as with the performance of the test hybrids for these two traits. The occurrence of positive correlation between seed yield of the inbred lines and test hybrids suggested the importance of the genes exerting additive effect for high seed yield in the hybrids. Very little or almost no heterosis was found for the other agronomic traits as well as for seed oil and protein content. While comparing the two breeding methods, no significant difference was found for seed yield of the test hybrids or the level of MPH; however, the BC1-derived inbred and test hybrid populations flowered and matured earlier and had longer grain-filling period than the F2-derived population. Thus, the results suggested that the B. oleracea gene pool can be used in the breeding of spring B. napus canola to improve seed yield in hybrid cultivars.

Organelle genome composition and candidate gene identification for Nsa cytoplasmic male sterility in Brassica napus

BackgroundNsa cytoplasmic male sterility (CMS) is a novel alloplasmic male sterility system derived from somatic hybridization between Brassica napus and Sinapis arvensis. Identification of the CMS-associated gene is a prerequisite for a better understanding of the origin and molecular mechanism of this CMS. With the development of genome sequencing technology, organelle genomes of Nsa CMS line and its maintainer line were sequenced by pyro-sequencing technology, and comparative analysis of the organelle genomes was carried out to characterize the organelle genome composition of Nsa CMS as well as to identify the candidate Nsa CMS-associated genes.ResultsNsa CMS mitochondrial genome showed a higher collinearity with that of S. arvensis than B. napus, indicating that Nsa CMS mitochondrial genome was mainly derived from S. arvensis. However, mitochondrial genome recombination of parental lines was clearly detected. In contrast, the chloroplast genome of Nsa CMS was highly collinear with its B. napus parent, without any evidence of recombination of the two parental chloroplast genomes or integration from S. arvensis. There were 16 open reading frames (ORFs) specifically existed in Nsa CMS mitochondrial genome, which could not be identified in the maintainer line. Among them, three ORFs (orf224, orf309, orf346) possessing chimeric and transmembrane structure are most likely to be the candidate CMS genes. Sequences of all three candidate CMS genes in Nsa CMS line were found to be 100% identical with those from S. arvensis mitochondrial genome. Phylogenetic and homologous analysis showed that all the mitochondrial genes were highly conserved during evolution.ConclusionsNsa CMS contains a recombined mitochondrial genome of its two parental species with the majority form S. arvensis. Three candidate Nsa CMS genes were identified and proven to be derived from S. arvensis other than recombination of its two parental species. Further functional study of the candidate genes will help to identify the gene responsible for the CMS and the underlying molecular mechanism.

Potential of the C Genome of Different Variants of Brassica oleracea for the Improvement of Agronomic and Seed Quality Traits of B. napus Canola

ABSTRACTThe narrow genetic base of Brassica napus L. canola, especially of its C genome, is an impediment for continued improvement of this crop. We investigated the gene pools of different variants of B. oleracea L. to improve agronomic and seed quality traits of B. napus canola. For this, B. napus canola inbred populations were developed from six interspecific crosses, involving a single B. napus canola line and six accessions of B. oleracea belonging to four variants of this species, following two breeding techniques (F2– and BC1–derived lines). Among these, the population derived from crossing with var. italica gave the greatest seed yield and also had shorter duration of flowering than most of the other populations. The population developed using var. botrytis had the highest seed oil content, and seed yield was comparable with the population developed using var. italica. Populations based on var. capitata had the lowest oil but greater protein content than most of the populations. Several lines from these interspecific crosses exceeded seed yield of the B. napus parent and also had acceptable agronomic and seed quality traits. Comparing the two breeding techniques, the F2–derived population gave greater yield than the BC1–derived population, whereas the BC1–derived population flowered and matured earlier than the F2–derived population. Genetic distance of the inbred lines from the B. napus parent showed positive correlation of r ≥ 0.4 with days to flowering and seed protein content and negative correlation with seed oil content, whereas correlation with seed yield was negative and weak (r = −0.18). Thus, the results showed that the B. oleracea gene pool, especially var. italica and botrytis, can be used to improve spring B. napus canola, as well as to broaden the genetic base of this crop.

Mapping and Identifying a Candidate Gene (Bnmfs) for Female-Male Sterility through Whole-Genome Resequencing and RNA-Seq in Rapeseed (Brassica napus L.).

In oilseed crops, carpel and stamen development play vital roles in pollination and rapeseed yield, but the genetic mechanisms underlying carpel and stamen development remain unclear. Herein, a male- and female-sterile mutant was obtained in offspring of a (Brassica napus cv. Qingyou 14) × (Qingyou 14 × B. rapa landrace Dahuang) cross. Subsequently, F2–F9 populations were generated through selfing of the heterozygote plants among the progeny of each generation. The male- and female-sterility exhibited stable inheritance in successive generations and was controlled by a recessive gene. The mutant kept the same chromosome number (2n = 38) as B. napus parent but showed abnormal meiosis for male and female. One candidate gene for the sterility was identified by simple sequence repeat (SSR) and insertion deletion length polymorphism (InDel) markers in F7–F9 plants, and whole-genome resequencing with F8 pools and RNA sequencing with F9 pools. Whole-genome resequencing found three candidate intervals (35.40–35.68, 35.74–35.75, and 45.34–46.45 Mb) on chromosome C3 in B. napus and candidate region for Bnmfs was narrowed to approximately 1.11-Mb (45.34–46.45 M) by combining SSR and InDel marker analyses with whole-genome resequencing. From transcriptome profiling in 0–2 mm buds, all of the genes in the candidate interval were detected, and only two genes with significant differences (BnaC03g56670D and BnaC03g56870D) were revealed. BnaC03g56870D was a candidate gene that shared homology with the CYP86C4 gene of Arabidopsis thaliana. Quantitative reverse transcription (qRT)-PCR analysis showed that Bnmfs primarily functioned in flower buds. Thus, sequencing and expression analyses provided evidence that BnaC03g56870D was the candidate gene for male and female sterility in the B. napus mutant.

Cytogenetic and Molecular Characterization of B-Genome Introgression Lines of Brassica napus L.

Brassica napus introgression lines (ILs), having B-genome segments from B. carinata, were assessed genetically for extent of introgression and phenotypically for siliqua shatter resistance. Introgression lines had 7–9% higher DNA content, were meiotically stable, and had almost normal pollen fertility/seed set. Segment introgressions were confirmed by fluorescent genomic in situ hybridization (fl-GISH), SSR analyses, and SNP studies. Genotyping with 48 B-genome specific SSRs detected substitutions from B3, B4, B6, and B7 chromosomes on 39 of the 69 ILs whereas SNP genotyping detected a total of 23 B-segments (≥3 Mb) from B4, B6, and B7 introgressed into 10 of the 19 (C1, C2, C3, C5, C6, C8, C9, A3, A9, A10) chromosomes in 17 ILs. The size of substitutions varied from 3.0 Mb on chromosome A9 (IL59) to 42.44 Mb on chromosome C2 (IL54), ranging from 7 to 83% of the recipient chromosome. Average siliqua strength in ILs was observed to be higher than that of B. napus parents (2.2–6.0 vs. 1.9–4.0 mJ) while siliqua strength in some of the lines was almost equal to that of the donor parent B. carinata (6.0 vs.7.2 mJ). These ILs, with large chunks of substituted B-genome, can prove to be a useful prebreeding resource for germplasm enhancement in B. napus, especially for siliqua shatter resistance.

Broadening genetic diversity inBrassica napuscanola: Development of canola-quality springB. napusfromB. napus×B. oleraceavar.alboglabrainterspecific crosses

Rahman, H., Bennett, R. A. and Séguin-Swartz, G. 2015. Broadening genetic diversity in Brassica napus canola: Development of canola-quality spring B. napus from B. napus × B. oleracea var. alboglabra interspecific crosses. Can. J. Plant Sci. 95: 29–41. The narrow genetic base in spring Brassica napus (AACC) canola is a limitation for continued improvement of this crop. This research focused on broadening of genetic diversity in spring canola by using B. oleracea (CC). Seeds of B. oleracea contain high levels of erucic acid and glucosinolates, which are undesired in canola. Therefore, inheritance of these traits and the prospect of developing spring canola with allelic diversity introgressed from B. oleracea were investigated in B. napus×B. oleracea interspecific progenies. Zero-erucic plants in F2generation occurred at a lower frequency than expected based on segregation involving only the C-genome erucic acid alleles. Selection in F2to F3focused on zero erucic acid, while focus in later generation was for low glucosinolate and B. napus plants. In the F6, 31% zero-erucic families had low glucosinolate content. Flow cytometry analysis of the F8families showed no significant difference from the B. napus parent. Genetic diversity analysis by using simple sequence repeat markers from the C-genome chromosomes showed that the F8families received up to 54% alleles from B. oleracea. The results demonstrate the feasibility of enriching genetic diversity in B. napus canola by using B. oleracea.

Identification of putative quantitative trait loci associated with a flavonoid related to resistance to cabbage seedpod weevil (Ceutorhynchus obstrictus) in canola derived from an intergeneric cross, Sinapis alba × Brassica napus.

Kaempferol 3- O -sinapoyl-sophoroside 7- O -glucoside was putatively identified as the major component of a characteristic HPLC peak previously correlated with the reduction of cabbage seedpod weevil larval infestation in a novel canola genotype. The cabbage seedpod weevil (Ceutorhynchus obstrictus [Marsham]) (CSPW) is a serious pest of brassicaceous oilseed crops such as canola in both Europe and more recently in North America. At present, the only control strategy against CSPW is the application of insecticides. As an alternative more environmentally-friendly control strategy, we developed novel canola germplasm resistant to weevil attack through introgression of Sinapis alba DNA into Brassica napus by making the wide cross followed by embryo rescue and backcrossing to the B. napus parent. We have previously characterized resistant canola lines by metabolic profiling and were able to correlate reduction of larval infestation to the presence of a characteristic HPLC peak. In this study, we have putatively identified the major component in the peak using mass spectrometry as kaempferol 3-O-sinapoyl-sophoroside 7-O-glucoside (KSSG). We have also identified quantitative trait loci (QTL) associated with this HPLC peak in a mapping population consisting of more than 200 individual doubled haploid (DH) lines derived from a cross between CSW428 (the resistant parent) and SC030686 (the susceptible parent). This QTL accounted for approximately 9.5% of the phenotypic variation in KSSG content. The observation that only one QTL was identified as surpassing the LOD threshold of 3.0 suggests that both parents may possess the positive alleles for other QTL that have not been detected in our study. This finding also indicates a complex regulatory mechanism for KSSG levels and provides an appropriate explanation for the large transgressive segregation observed in the DH lines of the QTL mapping population.

Broadening Genetic Diversity in Canola Using the C‐Genome Species Brassica oleracea L.

ABSTRACTGenetic diversity in spring type canola (Brassica napus L., AACC genome, 2n = 38) cultivars is narrow. Limited effort has been made to utilize genetic diversity from the diploid species Brassica oleracea L. (CC genome, 2n = 18) due to lack of canola quality traits in seeds of this species. The objectives of this study were to assess the feasibility of introgressing canola quality traits from B. napus into B. oleracea for the purpose of developing canola quality B. oleracea as well as development of B. napus with greater genetic diversity from B. oleracea while retaining canola quality traits. Two inbred (B. napus × B. oleracea) × B. oleracea populations were generated using B. napus ‘Hi‐Q’ and A01‐104NA and B. oleracea var. alboglabra (L. H. Bailey) Musil (Chinese kale). These populations were assessed for seed quality, effectiveness of selection based on morphological traits, genetic diversity using simple sequence repeat (SSR) markers, and ploidy levels using flow cytometry and cytological analysis of meiotic chromosomes. Zero‐erucic and low glucosinolate types were recovered from a relatively small segregating population. Morphological grouping could not reliably be used to select B. oleracea plants with 2n = 18; all BC1S6 families had nuclear DNA content similar to the B. napus parents. Marker analysis revealed a high level of B. oleracea alleles among backcross lines. These findings suggest that introgression of genetic diversity from the diploid B. oleracea C‐genome into stable, canola quality B. napus type lines is feasible and may have great potential in developing genetically diverse spring type varieties.

Exploitation of the late flowering species Brassica oleracea L. for the improvement of earliness in B. napus L.: an untraditional approach

The oilseed Brassica rapa flowers and matures earlier than B. oleracea, as well as their amphidiploid B. napus. Therefore, earliness of B.rapa has been investigated as a source of variation for earliness in B. napus breeding programs. Variation for days to flower exists in B. oleracea; however, its earliest flowering variant B. alboglabra flowers 2–3 weeks later than B. napus. We hypothesized that the C genome of B. alboglabra carries alleles for early flowering which are different from the C-genome alleles of B. napus; and these alleles can be used for the improvement of B. napus. To test this, we examined flowering time in pedigree and DH populations from two B. napus × B. alboglabra crosses. A B. napus line with about a week earlier flowering than the B. napus parent was achieved through reconstitution of its C genome following pedigree selection. Introgression of the B. alboglabra allele in the early flowering pedigree lines is also evident from the presence of B. alboglabra-specific SSR alleles in this line. However, application of doubled haploidy failed to generate any line that flowered earlier than the B. napus parent, which is probably due to the difficulty of obtaining large numbers of euploid B. napus DH lines from this interspecific cross. Thus, we demonstrate that a trait of the diploid species, which apparently looks undesirable, might in fact be highly valuable for the improvement of amphidiploids; and knowledge from this research can also be applied for other traits.

Brassica B-genome resistance to stem rot (Sclerotinia sclerotiorum) in a doubled haploid population of Brassica napus × Brassica carinata

Stem rot (caused by Sclerotinia sclerotiorum) is an important fungal disease of canola (Brassica napus), causing significant yield losses worldwide. Sources of genetic resistance to this disease in B. napus are scarce; however, Brassica species carrying the B-genome have been reported to possess high levels of resistance to stem rot. In order to transfer resistance from B. carinata to B. napus, an interspecific cross of B. napus × B. carinata was carried out and a doubled-haploid (DH) population was developed from BC2S3 plants. Fifty-eight DH lines, of which two carried B-genome linkage groups, and nine accessions of the diploid and amphidiploid Brassica species were screened in a growth chamber for resistance to stem rot. The B. napus parent (‘Westar’) and all B. rapa and B. oleracea reference lines were susceptible to sclerotinia stem rot, while the B. carinata parent as well as the B. nigra and B. juncea reference lines were resistant to this disease. Significant variation for the response to sclerotinia stem rot was found in the DH lines. The two DH lines carrying B-genome chromosomes showed significant (P < 0.01) resistance compared to the species without B-genome chromosomes. However, some of the DH lines, in which no B-genome introgression was apparent, also showed good resistance to this disease. Broad-sense heritability was estimated to be H = 54% for S. sclerotiorum-induced lesion length in this population.

Production and genetic analysis of partial hybrids from intertribal sexual crosses betweenBrassica napusandIsatis indigoticaand progenies

With the dye and medicinal plant Isatis indigotica (2n = 14) as pollen parent, intertribal sexual hybrids with Brassica napus (2n = 38, AACC) were obtained and characterized. Among a lot of F1 plants produced, only five hybrids (H1-H5) were distinguished morphologically from female B. napus parents by showing low fertility and some characters of I. indigotica, and also by having different chromosome numbers. H1-H4 had similar but variable chromosome numbers in their somatic and meiotic cells (2n = 25-30), and H5 had 2n = 19, the same number as the haploid of B. napus. GISH analysis of the cells from H1 and H5 detected one I. indigotica chromosome and one or two chromosome terminal fragments. New B. napus types with phenotypic and genomic alterations were produced by H1 after pollination by B. napus and selfing for several generations, and by H5 after selfing. A progeny plant (2n = 20) was derived from H1 after pollination by I. indigotica twice and had a phenotype similar to a certain type of B. rapa, showing that hybrid H1 likely retained all chromosomes of the A genome and lost some of the C genome in parental B. napus. The reasons for the formation of the partial hybrids with unexpected chromosomal complements and for the chromosome elimination are discussed.

Allelic diversity in a novel gene pool of canola-quality Brassica napus enriched with alleles from B. rapa and B. carinata

Brassica napus is an amphidiploid with genome AACC and is relatively deficient in genetic diversity. The abundant genetic diversity in other A- and C-genome Brassica species is a valuable resource to expand the narrow gene pool of B. napus. Recently the Ar genomic components from Chinese B. rapa (ArAr) and Cc genomic components from Ethiopian mustard B. carinata (BBCcCc) were introgressed into B. napus through interspecific hybridisation, and the Ar/Cc components were enriched through two generations of molecular marker-assisted selection. In this study, the simple sequence repeat (SSR) allelic diversity of 29 of these new-type B. napus lines, 12 from the first generation and 17 from the second generation, was compared with 66 international B. napus varieties from Australia, China and other countries. Hierarchical clustering and two-dimensional multidimensional scaling revealed that second generation lines and a few first generation lines, all selected for high Ar/Cc components, formed a unique population that was distantly separated from international B. napus. This novel gene pool had significantly higher richness of private SSR alleles and more alleles per SSR marker than the international B. napus varieties. The new-type B. napus lines showed variation in agronomic traits beyond the canola-quality B. napus parent. Many of the lines had low erucic acid and low glucosinolates in the seed (canola quality), indicating that they could be utilised immediately in canola breeding programs.

Production and characterization of intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus and their backcrossing progenies

Alien chromosome addition lines have been widely used for identifying gene linkage groups, assigning species-specific characters to a particular chromosome and comparing gene synteny between related species. In plant breeding, their utilization lies in introgressing characters of agronomic value. The present investigation reports the production of intergeneric somatic hybrids Brassica napus (2n = 38) + Orychophragmus violaceus (2n = 24) through asymmetric fusions of mesophyll protoplasts and subsequent development of B. napus-O. violaceous chromosome addition lines. Somatic hybrids showed variations in morphology and fertility and were mixoploids (2n = 51-67) with a range of 19-28 O. violaceus chromosomes identified by genomic in situ hybridization (GISH). After pollinated with B. napus parent and following embryo rescue, 20 BC(1) plants were obtained from one hybrid. These exhibited typical serrated leaves of O. violaceus or B. napus-type leaves. All BC(1) plants were partially male fertile but female sterile because of abnormal ovules. These were mixoploids (2n = 41-54) with 9-16 chromosomes from O. violaceus. BC(2) plants showed segregations for female fertility, leaf shape and still some chromosome variation (2n = 39-43) with 2-5 O. violaceus chromosomes, but mainly containing the whole complement from B. napus. Among the selfed progenies of BC(2) plants, monosomic addition lines (2n = 39, AACC + 1O) with or without the serrated leaves of O. violaceus or female sterility were established. The complete set of additions is expected from this investigation. In addition, O. violaceus plants at diploid and tetraploid levels with some variations in morphology and chromosome numbers were regenerated from the pretreated protoplasts by iodoacetate and UV-irradiation.

Chromosome elimination and fragment introgression and recombination producing intertribal partial hybrids from Brassica napus × Lesquerella fendleri crosses

The intertribal sexual hybrids between three Brassica napus (2n=38) cultivars and Lesquerella fendleri (2n=12) with the latter as pollen parent were obtained and characterized for their phenotypes and chromosomal and genomic constitutions. F(1) plants and their progenies mainly resembled female B. napus parents, while certain characters of L. fendleri were expressed in some plants, such as longer flowering period, basal clustering stems and particularly the glutinous layer on seed coats related to drought tolerance. Twenty-seven F(1) plants were cytologically classified into five types: type I (16 plants) had 2n=38, type II (2) had 2n=38-42, type III (3) had 2n=31-38, type IV (5) had 2n=25-31, and type V (1) had 2n=19-22. Some hybrids and their progenies were mixoploids in nature with only 1-2 chromosomes or some chromosomal fragments of L. fendleri included in their cells. AFLP (Amplified fragments length polymorphism) analysis revealed that bands absent in B. napus, novel for two parents and specific for L. fendleri appeared in all F(1) plants and their progenies. Some progenies had the modified fatty acid profiles with higher levels of linoleic, linolenic, eicosanoic and erucic acids than those of B. napus parents. The occurrence of these partial hybrids with phenotypes, genomic and fatty acid alterations resulted possibly from the chromosome elimination and doubling accompanied by the introgression of alien DNA segments and genomic reorganization. The progenies with some useful traits from L. fendleri should be new and valuable resource for rapeseed breeding.

Development of Novel Brassica napus lines with canola quality and higher levels of oleic and linoleic acids derived from intergeneric hybrids between B. napus and Orychophragmus violaceus

Brassica napus L. with more than 80% acreage of brassicas in China was introduced only in the last century with limited genetic variability. The widening of gene pool of this crop through suitable approaches including wide hybridizations is pivotal for its further improvement. In this study, new B. napus inbred lines with flowers having different petal colors (white, slight yellow and yellow), high productivity and with increased levels of oleic (∼70%, 10% higher than that of B. napus parent) and linoleic (28%) acids and reduced glucosinolate content (<30 μmol/g oil free meal) were obtained by pedigree selection through F12 generation in the progenies of one B. napus cv. Oro × Orychophragmus violaceus F5 hybrid plant (2n = 31) which had slight yellow petals. These lines possessed the same chromosome numbers as B. napus (2n = 38) with normal chromosome pairing (19 bivalents) and segregation (19:19) in their pollen mother cells and showed normal seed-set. These novel lines provide valuable germplasm with new gene source of low glucosinolate content for the breeding of canola rapeseed.

Introgression of Resistance to Cabbage Seedpod Weevil to Canola from Yellow Mustard

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is an insect pest of major economic importance in the production of canola (Brassica napus L. and B. rapa L.) in Europe and North America. Studies were conducted to test intergeneric germplasm, produced by crossing Sinapis alba L. (yellow mustard) × B. napus and then backcrossing progeny to the B. napus parent, as potential sources of resistance to the weevil. Of 230 intergeneric genotypes evaluated in field trials in 2001, 18 had an average of fewer than 0.05 weevil exit holes per pod, a level of resistance selected as conferring appropriate resistance and used for further testing. Subsequent tests confirmed several genotypes that evidently carried genes for resistance to C. obstrictus from the S. alba parent. In field assessments, mean exit holes per pod in the common commercial variety, B. napus cv. Q2, ranged from approximately 2.5 to 8.3 times more than those observed in the resistant lines. Some genotypes appeared to exhibit both antixenotic and antibiotic resistance to C. obstrictus, as indicated by fewer eggs laid per pod and larval development that was significantly lengthened in the resistant germplasm compared with the B. napus check. Introgression produced several genotypes with resistance to cabbage seedpod weevil that can now be crossed with agronomically superior B. napus germplasm; when the weevil‐resistant canola is available to producers it can comprise an important component in the integrated management of this pest, resulting in substantial reductions in insecticide use in this crop.

GISH and AFLP analyses of novel Brassica napus lines derived from one hybrid between B. napus and Orychophragmus violaceus

New Brassica napus inbred lines with different petal colors and with canola quality and increased levels of oleic (approximately 70%, 10% higher than that of B. napus parent) and linoleic (28%) acids have been developed in the progenies of one B. napus cv. Oro x Orychophragmus violaceus F5 hybrid plant (2n = 31). Their genetic constituents were analyzed by using the methods of genomic in situ hybridization (GISH) and amplified fragments length polymorphism (AFLP). No intact chromosomes of O. violaceus origin were detected by GISH in their somatic cells of ovaries and root tips (2n = 38) and pollen mother cells (PMCs) with normal chromosome pairing (19 bivalents) and segregation (19:19), though signals of variable sizes and intensities were located mainly at terminal and centromeric parts of some mitotic chromosomes and meiotic bivalents at diakinesis or chromosomes in anaphase I groups and one large patch of chromatin was intensively labeled and separated spatially in some telophase I nuclei and metaphase II PMCs. AFLP analysis revealed that substantial genomic changes have occurred in these lines and O. violaceus-specific bands, deleted bands in 'Oro' and novel bands for two parents were detected. The possible mechanisms for these results were discussed.

Detection of Chromosomal Rearrangements Derived From Homeologous Recombination in Four Mapping Populations of Brassica napus L.

Genetic maps of Brassica napus were constructed from four segregating populations of doubled haploid lines. Each mapping population had the same male parent and used the same set of RFLP probes, facilitating the construction of a consensus map. Chromosomal rearrangements were identified in each population by molecular marker analysis and were classified as de novo homologous nonreciprocal transpositions (HNRTs), preexisting HNRTs, and homologous reciprocal transpositions (HRTs). Ninety-nine de novo HNRTs were identified by the presence of a few lines having duplication of a chromosomal region and loss of the corresponding homologous region. These de novo HNRTs were more prevalent in one population that had a resynthesized B. napus as a parent. Preexisting HNRTs were identified by fragment duplication or fragment loss in many DH lines due to the segregation of HNRTs preexisting in one of the parents. Nine preexisting HNRTs were identified in the three populations involving natural B. napus parents, which likely originated from previous homologous exchanges. The male parent had a previously described HRT between N7 and N16, which segregated in each population. These data suggest that chromosomal rearrangements caused by homologous recombination are widespread in B. napus. The effects of these rearrangements on allelic and phenotypic diversity are discussed.

Intergeneric hybrids between Brassica napus and Orychophragmus violaceus containing traits of agronomic importance for oilseed rape breeding.

Protoplast fusions between Brassica napus and Orychophragmus violaceus for transfer of valuable traits to oilseed rape resulted in 257 somatic hybrid plants. Hybridity was confirmed by morphological, cytological and molecular means. Symmetric fusions gave rise to 131 plants. Fifty eight of these plants had an intermediate morphology and contained nuclear DNA corresponding to the sum of the parental species. All 131 plants were sterile with no pollen grains observed upon flowering. Another 126 plants were derived from asymmetric fusions in which protoplasts of the donor parent O. violaceus were irradiated by 100 or 200-Gy X-rays prior to fusion. Morphologically these plants showed a larger variation compared to the plants regenerated from symmetric fusion experiments. In contrast to plants obtained from symmetric fusions, fertile hybrids were recovered among regenerants from the asymmetric fusions. Twenty four of these plants released viable pollen grains and 14 of the determined 17 plants set seeds after either selfing or backcrossing to B. napus. Fourteen male-sterile plants were identified with female fertility. This observed male sterility most-likely originated from alloplasmic recombination and would be of great potential for the development of a new cytoplasmic male sterility system. The fatty acid composition of the fertile hybrids and their progenies showed a biased distribution towards the B. napus parent, which has a high erucic acid-content type. However, increased levels of palmitic and linoleic acids compared to B. napus were found in subsequent generations, as well as a reduced level of erucic acid.