Self-incompatibility interactions in Brassica napus

Summary The interactions of nine S-gene lines of Brassica napus were examined. Seven different S-genes were involved in the crosses, with three lines of different origin having the same S-gene. In general, the reactions on selfing the heterozygotes were as expected from the results of test crosses with the homozygous parent lines. All types of dominance relationships were found, including reversal of dominance in pollen and pistil. Weakening of activity of one or both genes was found in several cases. Background genotype was found have to some effect and reciprocal differences in reactions were also observed.     

Interspecific hybridization of Brassica napus and B. juncea through ovary,ovule and embryo culture

Summary Employing in vitro culture of ovaries, ovules and embryos, interspecific hybrids have been obtained amongst two important oilseed crops, Brassica napus x B. juncea and their reciprocal. The test-tube hybrid plants have been transferred to the field, and reared to maturity. The F₁ seeds obtained from the hybrid ovaries showed normal germination, and the hybrid plants exhibited a range of variation of characters.     

Production of fertile transgenic Brassica napus by Agrobacterium-mediated transformation of protoplasts

A protocol for Agrobacterium tumefaciens‐mediated transformation of Brassica napus mesophyll protoplasts is described. A strain with a neomycin phosphotransferase (nptII) gene and a KCS gene under control of a napin promoter was used at co‐cultivation. Transformed protoplasts were regenerated to fertile and morphologically normal transgenic plants. Transformants were confirmed by PCR of the nptII gene and NAP/KCS expression cassette, and Southern blot analysis. Seeds of the transformants showed a changed fatty acid profile: two transformants had a higher erucic acid level and differed significantly from that of B. napus. Genetic analysis of the progeny revealed that the kanamycin resistance introduced was inherited in a Mendelian fashion.     

Evaluation of microspore-derived embryos as models for studying lipid biosynthesis in seed of rapessed (Brassica napus L.)

Summary Microspore culture of rapeseed (Brassica napus L.) has provided a powerful tool not only for breeding but also in developmental studies. In this study, microspore-derived embryos (MDE) of B. napus were evaluated as a model in seed for studying accumulations of triacylglyceride (TAG) fatty acids in both a low and high erucic acid rapeseed line; and accumulations of TAG and free fatty acids (FFA) in a high erucic acid rapessed line. The accumulation patterns confirmed that MDE had a similar TAG fatty acid profile to seed during the embryo development within each genotype. The oil accumulation in MDE after 36 days in culture (DIC) approached levels similar to those in zygotic seed 25 days after flowering (DAF). Significant differences were detected in contents of both total free fatty acids and specific free fatty acids between MDE and seed. During the developmental period, total free fatty acids changed from 16% to 2.1% in MDE, but from 10.5% to 0.1% in seed. MDE had much higher percentage of free linolenic and erucic acids than seed, particularly during the late developmental stages. The current study indicated that MDE can be used as a model to study TAG and TAG fatty acids in seed but caution must be taken to study free fatty acid metabolism.     

Inbreeding and selection in swedes (Brassica napus ssp rapifera)

Summary The effect of inbreeding and selection within the old swede cultivar Scotia was examined. A decline in yield was shown by lines produced by selfing from the highest yielding progenies selected after open pollination. It is assumed that these progenies were from heterozygous plants. The yield of two groups of lines did not decline and from these, after a second generation of selfing, eight lines were selected with a mean dry matter yield 10 per cent higher than Scotia.Now part of Scottish Crop Research Institute, Dundee, Scotland.     

Oligonucleotide fingerprinting of resynthesized Brassica napus

Brassica napus plants, artificially synthesized through somatic hybridization of B. oleracea and B. campestris protoplasts, were analyzed by oligonucleotide fingerprinting. While the fingerprint patterns of the different hybrid plants looked very much alike, they did not simply represent a combination of the parental patterns. Instead, the absence of parental bands as well as the presence of new bands suggest that elimination and/or rearrangements occurred during or after the fusion of the two genomes. The fingerprints of individual F1 progeny plants of selfed hybrids did not detect major changes. Thus, once formed, the artificially resynthesized amphidiploid B. napus genome appears to be stable. Taken together, our experiments demonstrate the usefulness of oligonucleotide fingerprinting for the characterization of artificial hybrids in the genus Brassica.     

Effect of donor plant age and inflorescence age on microspore culture of Brassica napus L.

Summary Effect of age of donor plants and age of inflorescence on embryogenesis in microspore culture of B. napus was examined. Microspores isolated from buds of older plants had a higher embryo yield than those of younger ones. The effect of the age of inflorescence showed a different pattern. In older plants, a higher embryogenesis response was observed in microspores isolated from buds of new inflorescences, while in young plants, microspores isolated from buds of old inflorescences showed high embryo yield. These different responses were considered to be attributable to a difference in the developmental stage of pollen at the time of microspore isolation. Our results indicated that microspores collected from older inflorescences and older plants have sufficient embryogenic potential when the optimum developmental stage of pollen was used. Frequency of embryo to plant conversion was influenced by the size of embryos subcultured, but not by donor plant age or the age of the inflorescence.     

Intergeneric hybrid between Brassica napus and Diplotaxis harra through ovary culture and the cytogenetic analysis of their progenies

Brassica napus (2n = 38) and Diplotaxis harra (2n = 26) were used to investigate gene transfer from D. harra to B. napus. Intergeneric F₁ hybrids (dihaploid 2n = 32 chromosomes) were obtained through ovary culture. The chromosome associations in the first meiotic division was (0–2)_III + (2–10)_II + (12–28)_I. Many seeds were harvested in the F₁ hybrid after backcrossing with B. napus, and from open pollination of the F₁ hybrid. Somatic chromosome numbers of BC₁ and hybrid plants varied from 2n = 26 to 52. In the first meiotic division, high frequencies of bivalent association and relatively low pollen fertility were observed. BC₂ plants generated from the BC₁ plants with 2n = 38 chromosomes, 69.6% showed 2n = 38 chromosomes. Many aneuploids with addition and deletion of chromosomes were also obtained. A bridge plant between B. napus and D. harra with 2n = 32 chromosomes should be valuable material for the breeding of brassica crops.     

Inheritance of seed colour in Brassica campestris L. and breeding for yellow-seeded B. napus L.

Summary Seed colour inheritance was studied in five yellow-seeded and one black-seeded B. campestris accessions. Diallel crosses between the yellow-seeded types indicated that the four var. yellow sarson accessions of Indian origin had the same genotype for seed colour but were different from the Swedish yellow-seeded breeding line. Black seed colour was dominant over yellow. The segregation patterns for seed colour in F₂ (Including reciprocals) and BC₁ (backcross of F₁ to the yellow-seeded parent) indicated that the black seed colour was conditioned by a single dominant gene. Seed colour was mainly controlled by the maternal genotype but influenced by the interplay between the maternal and endosperm and/or embryonic genotypes. For developing yellow-seeded B. napus genotypes, resynthesized B. napus lines containing genes for yellow seed (Chen et al., 1988) were crossed with B. napus of yellow/brown seeds, or with yellow-seeded B. carinata. Yellow-seeded F₂ plants were found in the crosses that involved the B. napus breeding line. However, this yellow-seeded character did not breed true up to F₄. Crosses between a yellow-seeded F₃ plant and a monogenomically controlled black-seeded B. napus line of resynthesized origin revealed that the black-seeded trait in the B. alboglabra genome was possibly governed by two independently dominant genes with duplicated effect. Crossability between the resynthesized B. napus lines as female and B. carinata as male was fairly high. The sterility of the F₁ plants prevented further breeding progress for developing yellow-seeded B. napus by this strategy.     

Genetic effects on biomass yield in interspecific hybrids between Brassica napus and B. rapa

This study was conducted to estimate the genetic effects on biomass yield in the interspecific hybrids between Brassica napus and B. rapa, and to evaluate the relationship between parental genetic diversity and its effect on biomass yield of interspecific hybrids. Six cultivars and lines of oilseed B. napus and 20 cultivars of oilseed B. rapa from different regions of the world were chosen to produce interspecific hybrids using NC design II. Obvious genetic differences between B. rapa and B. napus were detected by RFLP. In addition, Chinese B. rapa and European B. rapa were shown genetically differences. Plant biomass yield from these interspecific hybrids were measured at the end of flowering period. Significant differences were detected among general combining ability (GCA) effects over two years and specific combining ability (SCA) effects differences were detected in 2000. The ratios of mean squares, (σ² _GCA(f) + σ² _GCA(m)) / (σ² _GCA(f) + σ² _GCA(m) + σ² _SCA), were 89% and 88% in 1999 and 2000, respectively. This indicates that both additive effects and non-additive effects contributed to the biomass yield of interspecific hybrids and the former played more important role. Some European B. rapa had significant negative GCA effects while many of Chinese B. rapa had significant positive GCA effects, indicating that Chinese B. rapa may be a valuable source for transferring favorable genes of biomass yield to B. napus. Significant positive correlation between parental genetic distance and biomass yield of interspecific hybrids implies that larger genetic distance results in higher biomass yield for the interspecific hybrids. A way to utilize interspecific heterosis for seed yield was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation in flowering response to pre-vernalisation growth in swedes (Brassica napus ssp. rapifera)

Summary The effect of pre-vernalisation growth (pre-growth) period on time of flowering was examined in four lines of swedes. No effect was found with the line from cv. Marian. The lines from cvs. Ruta Øtofte and Bangholm Wilby showed increases in time to flowering with increased pre-growth period; maximum delay occurred with 4 wk and 6 wk pre-growth, respectively. Most plants from a line of cv. Criffel showed no effects, but a small proportion did show long delays with pre-growth.     

Genetic variation of tocopherol content in a germplasm collection of Brassica napus L.

The genetic variation for tocopherol contents was investigated in a very divergent collection of 87 winter rapeseed genotypes grown in the greenhouse and in two years in the field. Genotypic and environmental effects were highly significant for alpha-, gamma- and total tocopherol contents and the alpha-/gamma-tocopherol ratio. Field and greenhouse environments differed significantly (p < 0.001) for tocopherol traits, with greenhouse means up to 19% higher than field means. Alpha-tocopherol content ranged from 63 to157 mg kg^-1 seed, gamma-tocopherol content from 114 to 211 mg kg^-1 seed, total tocopherol content from 182 to367 mg kg^-1 seed, and the alpha-/gamma-tocopherol contents ratio from0.36 to 1.23. The resynthesized lines often have a remarkably low alpha-tocopherol content and consequently a low alpha-/gamma-tocopherol contents ratio. The lines with altered fatty acid composition displayed the highest variation for both tocopherol content and composition. No significant differences were observed among groups with different seed quality types [00], [0+] and [++]. Total tocopherol content was not correlated with the alpha-/gamma-tocopherol ratio, indicating that total tocopherol content is independent from tocopherol composition. Alpha- and gamma-tocopherol contents were also not correlated. Gamma-tocopherol contents showed a significant positive correlation with oil content (r = 0.34^**). This revised version was published online in July 2006 with corrections to the Cover Date.     

Interspecific transfer of Brassica juncea-type high blackleg resistance to Brassica napus

Summary Complete resistance to Leptosphaeria maculans, the cause of blackleg of oilseed rape (Brassica napus), was transferred from B. juncea to B. napus through an interspecific cross. B. juncea-type complete resistance (JR) was recognized first in one F₃ progeny (Onap^JR) by the absence of leaf-lesions on seedlings and canker-free adult plants. The commercially important characters of B. napus were retained in advanced lines of Onap^JR, which combined JR with low erucic acid levels (<0.5%), high seed yield and variable maturity dates.JR appeared to be inherited as a major gene or genes. Segregation for resistance and susceptibility contintied to occur during later generations of selection of Onap^JR. JR was readily transferred from Onap^JR to other suitable B. napus cultivars or lines with partial resistance to blackleg and resulted in highly vigorous carly generation selections adapted to cold, wet situations along with complete resistance to blackleg.     

Self-pollination in swedes (Brassica napus ssp Rapifera) and its implications for cultivar production

Summary The degree of selfing on open pollination was examined in four swede cultivars. Three cultivars had over 80 per cent selfing, whilst the fourth had less than 55 per cent. The inbreeding coefficient with these levels of selfing, assuming the cultivars were at equilibrium, would be 0.69 and 0.37 respectively. The cultivar with the high level of outcrossing was found to possess a degree of self-incompatibility. The structure of such populations is demonstrated, and the implications for cultivar production are discussed.     

The transfer of characters from Brassica campestris L. to Brassica napus L.: Production of clubroot-resistant oil-seed rape (B. napus ssp oleifera)

Summary Four oil-seed rape lines were crossed with a clubroot resistant Brassica campestris line from the European Clubroot Differential sct. The allotriploid hybrids were backcrossed to the rape lines to introgress clubroot resistance into oil-seed rape. Using a combination of screening for disease resistance and chromosome number, a high proportion of 38-chromosome, clubroot resistant selections were obtained.     

甘蓝型黄籽油菜自交系转化体系的建立

利用黄籽甘蓝型油菜自交系建立和优化了遗传转化系统。首先构建了由质粒pCNR与Δ6脂肪酸脱氢酶基因插入到植物的高效表达载体pCAMBIA2301G。利用在Murashige和Skoog培养基(含有200 mmol L^–1乙酰丁香酮)培养5~7 d的下胚轴外植体与农杆菌株LBA4404共培养63~69 h (pCNR),再于芽诱导培养基上培养3个月诱导芽再生。在最佳条件下,平均转化效率约为1.3%。转化植株的GUS分析和PCR分析结果表明,外源基因成功导入甘蓝型油菜。Southern杂交表明,这些转化子含有目标基因1~2个拷贝。用气相色谱分析转基因植物种子的脂肪酸,γ-亚麻酸含量达8.2%。     

Self-incompatibility in Brassica napus: seed set on crossing 19 self-incompatible lines

Summary Seed set after self-pollination confirmed that 19 lines of Brassica napus were self-incompatible. Eight lines, H, J, Q, W, X, K, P and Z, were fully cross-compatible. Line R was cross-compatible with these lines but often had a low seed set as female parent. These results are consistent with the activity of nine distinct S-alleles. Line S was cross-incompatible with K, as was V with P, and F with Z. With each of the lines A, E, B, O, G, L and M at least one reciprocal difference was found so that the number of additional distinct S-alleles could not be inferred, but there must be a minimum of seven.Pollen tube counts of intra- and inter-line pollinations using M, B and X confirmed the homozygosity of these lines with respect to self-incompatibility status and the presence of non-reciprocal compatibility between M and B.The results are interpreted in terms of the activity of both B. oleracea and B. campestris S-loci and the implications for hybrid breeding are discussed.     

外源SA影响油菜叶表皮蜡质及菌核病抗性的机制

处于植物地上部分最外层的表皮蜡质被认为是植物抵御病原物入侵的第一道屏障,但表皮蜡质是否及如何参与油菜菌核病防御机制还不清楚。本试验选用2个抗病性不同的油菜品种中双9号(抗性品种)和渝油19 (感病品种),对水杨酸(SA)处理后的油菜幼苗接种核盘菌,分析油菜病情指数、叶表皮蜡质含量和晶体结构特征、抗氧化酶活性的变化规律。结果表明,SA处理使中双9号病情指数显著下降,渝油19无显著变化,SA诱导了油菜抗性品种中双9号对菌核病的抗性。接种核盘菌后,中双9号PAL活性显著增加,而渝油19显著下降; SA处理植株叶片PAL和POD活性显著高于单纯接种植株。渝油19苗期叶表皮蜡质总量显著高于中双9号。SA诱导中双9号蜡质总量及组分含量增加,柱状晶体结构减少,片状结构增加,扩大了蜡质层覆盖叶表面积。渝油19在SA处理后蜡质含量无显著变化,晶体结构发生了与中双9号相似的变化,但渝油19蜡质晶体熔融后覆盖叶表面积小于中双9号。综合分析认为防御酶活性及叶表皮蜡质共同参与SA诱导中双9号抗性增强的过程。     

Identification of rape seed cultivars (Brassica napus) by starch gel electrophoresis of enzymes

Summary Isozyme patterns were used to characterize ten commercial rape seed (Brassica napus) cultivars. Extracts of cotyledons were made 4–7 days after germination and separated by electrophoresis on starch gels. A sample of more than 100 plants of each variety was analysed and stained for 4 polymorphic enzyme loci (Lap, Gpi, Acon, and Sdh). Therewith, it was possible to distinguish all ten rape varieties qualitatively by at least one typical enzyme pattern. Further, it could be demonstrated that all pairs of varieties showed clear qualitative differences in isozyme patterns, when only tow loci were screened (Acon, Sdh). Using ² test of homogeneity all pairs of varieties differ significantly in their frequencies of isozyme patterns for Acon and in all but one for Sdh.     

Selection for fast germination in rapeseed (Brassica napus L. and B. Campestris L.)

Summary Eleven populations of Brassica napus L. and twelve populations of B. campestris L. were subjected to three cycles of selection for fast germination at 2°C and at 25°C. The seeds from the selected populations, and unselected control populations grown in the same environment as the selected populations, were examined for germination behaviour at 2°C and 25°C, and for growth behaviour at 10°C. The populations in both species responded differently in terms of germination behaviour to selection for fast germination. In most of the populations that did respond positively to selection, selection practised at 2°C was superior to selection at 25°C in improving percent germination at 2°C, and was as good as the selection at 25°C in improving germination rate at the higher temperature. Selection for fast germination had no effect on growth characteristics of B. napus and B. campestris populations grown at 10°C. Thus, selection for fast germination at one low temperature may lead to improvement in germination characteristics over a range of temperatures, but will not necessarily lead to improved growth performance of the selected populations.