Superior performance of two homozygous diploid lines from naturally occurring polyhaploids in oilseed rape (Brassica napus)

Summary Homozygous diploids in oilseed rape were produced by pipetting drops of 0.1 per cent colchicine into the leaf axils of rooted cuttings from naturally occurring polyhaploids after removing the waxy covering with a scalpel. Trial results from spring and winter rape showed that occasional homozygous diploid lines yielded consistently more oil per ha than the parental varieties. Prospects for breeding oilseed rape as a self-fertilised crop are discussed.     

A genetic study of growth characters and yield characters of oilseed rape

Summary Analysis of single plants in parental, F₁ and F₂ populations of three crosses of oilseed rape indicated cytoplasmic effects in F₁ or F₂ generations for most of the observed characters. There was evidence of dominance for early flowering and early maturity. Heterosis was exhibited for yield and yield components. The heritabilities for the characters under study were generally very low.     

Relationships between seed yield and growth characters,yield components,seed quality of summer-type oilseed rape (Brassica napus L.)

Summary Five genotypes of rapeseed were observed in the field on a single plant and plot basis to evaluate growth characteristics, yield, yield components and seed quality. Observations were made in two years at two locations on three seeding date and three seeding rate treatments. Correlation of seed yield with growth characters demonstrated no consistent trend, indicating that an early maturity and high seed yield should be possible. Harvest index was strongly correlated with seed yield. Percent seed oil and protein were not directly related to seed yield.     

Self-incompatibility as a pollination control mechanism for spring oilseed rape,Brassica napus L.

Summary Self-incompatibility was shown to be an effective method of pollination control in spring rapeseed (B. napus L. ssp. oleifera (Metzg.)) by comparing the yield of a Westar-Topas syn-1 produced by crossing two SI lines with the yield of the corresponding syn-1 produced by hand pollination. Although the trial showed high-parent heterosis in the syn-1s, there was insufficient replication to determine the level of heterosis.Abbreviations SI self-incompatible - SC self-compatible     

Prediction of F6 line performance from F3 families in spring oilseed rape. I. Yield and other agronomic traits

Summary The reliability of a selection among crosses based on a cross prediction in early generations was investigated in spring rapeseed. The performance of the parents, the F₂ generation, and random F₃ lines from four crosses were used to predict the probability of finding superior recombinant lines. These predictions were made for two years and compared with the observed performance of F₆ lines in the second of these two years and in an additional year. Predicted and observed performances coincided reasonably for the characters plant height, standability, maturity and an index calculated from seed yield, oil content and protein content. For seed yield and flowering time, the predictions were very unreliable. In conclusion, prediction methods may be useful in rapeseed breeding, if quality traits are of major commercial interest.     

Predictive study of the advantages of cleistogamy in oilseed rape in limiting unwanted gene flow

Summary The aim of this study was to evaluate the interest of beginning the selection process on a new genetic characteristic, cleistogamy, to manage gene flow in oilseed rape. The first step was to introduce this characteristic in an existing model of gene flow between oilseed rape populations in time and space, GeneSys-Rape. The second step was to evaluate the parameters of the model linked to this characteristic using field experimentations. Cleistogamous oilseed rape was shown to have an autogamy rate as high as 94% and to emit 10 times less pollen than an open-flowered oilseed rape in the same conditions. But the cleistogamous character was also shown to be unstable in the genotypes tested. The third step was to evaluate the interest of cleistogamy using simulations comparing several genotypes with or without cleistogamy in two different cropping systems. These simulations showed that an oilseed rape both dwarf and cleistogamous was interesting to limit gene escape and that a 99%-autogamous oilseed rape was interesting to limit both gene escape from and harvest contamination of the 99%-autogamous oilseed rape.     

Hybridization of radish (Raphanus sativus L.) and oilseed rape (Brassica napus L.) through a flower-culture method

Summary Hybridization between radish and oilseed rape has been cumbersome, requiring elaborate embryo rescue techniques. With a modified flower culture method, we have achieved successful hybridization between radish and (transgenic) oilseed rape without the laborious and technically demandingin vitro ovule or embryo rescue techniques.The hybrid nature of the intergeneric hybrids was demonstrated using morphological traits, and DNA analyses. The described method will facilitate the generation ofRaphanobrassica hybrids useful for biosafety studies of the potential for transgenes to spread in weedyCruciferae as well as for breeding programs aimed at introducing useful radish genes, e.g. nematode resistance genes, into oilseed rape.     

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

Escape of transgenes from genetically modified oilseed rape, Brassica napus, into wild radish, Raphanus raphanistrum, depends on sexual compatibility. The variation in prezygotic barriers of two different cultivars for interspecific hybridization with a population of wild radish was investigated by hand crossing and fluorescence microscopy of pistils. Significant differences were observed between oil seed rape cultivars in their ability to accept wild radish pollen germinating onto their stigma and the rate of fertilization of ovules. Some differences among the pollen donor plants were also detected. These results suggest that the rate of interspecific hybridization in the field would depend upon the oilseed rape cultivar and the genotype composition of the local wild populations. The implication of S-related genes, as revealed through identification by pistil tissue prints of class I and II S-types of SLG (S-Locus Glycoprotein) and SLR1 (S-Locus Related),and immuno-IEF, was not significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Segregation and linkage analysis of DNA markers in microspore derived and F2 populations of oilseed rape (Brassica napus L.)

Summary The segregation of RFLP and RAPD markers was compared in two oilseed rape (Brassica napus L.) breeding populations from the cross Topas x R4, the latter being a low linolenic mutation line. A total progeny of 68 F₂ and 40 microspore derived plants were studied with 25 markers. The results indicated a significant excess of Topas alleles at five RAPD loci in the microspore derived population. This suggests that genomic regions which probably affect microspore culture ability do not have identical distribution in the two population types.     

RAPD markers linked to microspore embryogenic ability in Brassica crops

In order to identify the markers linked to microspore embryogenic ability in Brassica crops, RAPD segregation analyses were performed in a microspore-derived (MD) population and a F₂ population derived from F₁between ‘Ho Mei’ (high responsive parent in microspore embryogenesis) and ‘269’ (low responsive parent) in Chinese cabbage, and between ‘Lisandra’ (high responsive parent) and ‘Kamikita’ (low responsive parent) in oil seed rape. After 230 and 143 primers were screened, a total of 148 and 52markers were detected to be polymorphic between the parents in Chinese cabbage and oilseed rape, respectively. Twenty-seven percent of the markers in the MD population showed a significant segregation distortion in both crops. Of the markers showing segregation distortion in the MD population, 71–75% of the markers followed the expected Mendelian segregation ratio in the F₂ population. When the relationships between such distorted markers and microspore embryogenesis of the F₂ population were examined, 7 and 3 markers were identified to be associated with embryogenic ability in Chinese cabbage and oilseed rape, respectively. These markers showed additive effects on embryo yields, and the plants having more alleles of the high responsive parent produced higher embryo yields. These markers maybe useful in marker-assisted selection for improving microspore responsiveness straits in Brassica crops. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modification of oilseed rape to produce oils for industrial use by means of applied tissue culture methodology

Summary A programme of research was designed to investigate methods for the modification of the fatty acid profiles of high performance lines of oilseed rape (Brassica napus L.) in an attempt to produce lines with enhanced levels of industrially useful fatty acids. The methodology employed to achieve these objectives was based on the exploitation of somaclonal or protoclonal variation, and targeted somatic hybridization using wild cruciferous germplasm as fusion partners.A range of somaclonal lines was produced from shoot regeneration protocols. These lines underwent replicated, randomised glasshouse trials for morphological assessment followed by gas chromatographic analysis to monitor any changes in fatty acid profile. It was found that a small number of lines exhibited potentially useful changes in oleic acid and polyunsaturated fatty acid content. Protoplast regeneration and electrofusion protocols for a range of winter oilseed rape lines were developed, and methods for the isolation and fusion of protoplasts of the wild crucifer Lunaria annua (chosen for its high nervonic acid content) established.Abbreviations GC Gas Chromatography     

Transfer of disease resistance within the genus Brassica through asymmetric somatic hybridization

Summary Asymmetric somatic hybrid plants between Brassica napus L. (oilseed rape genome AACC) and a transgenic line of Brassica nigra L. Koch (black mustard genome BB) were tested for their resistance against rapeseed pathogens Phoma lingam (black leg disease) and Plasmodiophora brassicae (club root disease). The transgenic B. nigra line used (hygromycin-resistant, donor) is highly resistant to both fungi, whereas B. napus (recipient) is highly susceptible. The asymmetric somatic hybrids were produced using the donor-recipient fusion method (with X-irradiation of donor protoplasts) reported by Zelcer et al. (1978) for the production of cybrids. Using hygromycin-B for selection, a total of 332 hybrid calli were obtained. Regenerants, resistant or susceptible to both diseases, were selected. Many hybrids expressed resistance to only one pathogen. Dot blot experiments showed that the asymmetric hybrid plants contained varying amounts of the donor genomic DNA. Furthermore, a correlation was detected between the radiation dose and the degree of donor DNA elimination.     

Rapid and efficient screening of phosphinothricin tolerant oilseed rape (Brassica napus) with a novel germination test

A novel screening test is described for the discrimination of transgenic phosphinothricin tolerant oilseed rape from non transgenic rape seedlings. The method is based on the germination of rape seeds on filter paper soaked with a 0.005% phosphinothricin solution. Under these conditions inhibition of seedling development by the herbicide can be observed after 10 days. The germination test gains an advantage over the routinely used herbicide spraying, because it is rapid, needs little space and allows efficient screening of huge numbers of seeds. The assay has been successfully applied to the screening of different transgenic and non transgenic rapeseed varieties/lines and has been compared to other methods such asBasta® spray test, drop test, ELISA-technique and PCR-amplification of the pat gene. This test allows on one hand large screening programmes to monitor the foreign gene in the environment and on the other quality control of seedlots before market introduction of herbicide tolerant oilseed rape.     

Transfer of resistance to race 2 of Plasmodiophora Brassicae from Brassica napus to cabbage (B. oleracea var. Capitata). I. Interspecific hybridization between B. napus and B. oleracea var. Capitata

Summary Interspecific hybridization between Brassica napus L. (2n=38, a₁a₁c₁c₁) and B. oleracea var. capitata L. (2x- and 4x-cabbage; 2n=2x=18, cc and 2n=4x=36, cccc) was carried out for the purpose of transferring clubroot disease resistance from the amphidiploid species to cabbage. Nineteen hybrids with three different chromosome levels (2n=28, a₁c₁c; 2n=37, a₁c₁cc and 2n=55, a₁c₁cccc) were obtained. The F₁ plants were mostly intermediate between the two parents but as the number of c genomes in the hybrids increased, the more closely the hybrids resembled the cabbage parent. All F₁ hybrids were resistant when tested against race 2 of Plasmodiophora brassicae wor. The complete dominance of resistance over susceptibility suggested that the gene(s) controlling resistance to this particular race of the clubroot pathogen is probably located on a chromosome of the a genome in Brassica.Contribution No. J654.     

Heterosis and inbreeding depression in forage rape (Brassica napus L.)

Summary Heterosis and inbreeding depression for total fresh and dry weights were studied over two seasons in 15 crosses of six cultivars of forage rape (Brassica napus L.). Some of the hybrids exhibited considerable heterosis over both mid-parent and better parent; followed by depression in the F₂. The cross Windal × Canard had 62% and 25% greater dry matter yield over the best cultivar used in this experiment in 1978 and 1979, respectively. Possibilities of the utilization of this hybrid superiority are discussed.     

Contribution of host-pathogen interactions to the expression of the blackleg disease of spring rape (Brassica napus L.) caused by Leptosphaeria maculans (Desm.) Ces. et de not

Variation in the responses of selected genotypes of spring rape to infection by a wide range of isolates of Leptosphaeria maculans was analyzed in this study.Differences in severity of disease damage to seedlings between host and pathogen genotypes were highly significant. Interactions between host and pathogen were also highly significant. The generally resistant cultivar Wesreo was susceptible to a number of isolates whereas the normally susceptible cultivars Zollern-gold and Ceska were resistant to some isolates. Overall, however, Wesreo was resistant to a far greater number of isolates than were the susceptible genotypes.Significant differences in severity of disease damage were also observed between groups of isolates from different sites. All host genotypes were resistant to a substantially greater proportion of isolates from certain sites than from others. Interactions were again detected in that the ranking of sites on the basis of the proportion of isolates causing severe damage varied between host genotypes.The significance of host-pathogen interactions in the B. napus-L. maculans relationship is discussed with special reference to current views on the nature of horizontal resistance.     

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.     

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. oleracea var. capitata). II. Meiosis in the interspecific hybrids between B. napus and 2x and 4x cabbage

Summary Meiosis in 14 interspecific F₁ hybrids with three chromosomal levels (triploid, tetraploid, hexaploid; 2n=28, 37 and 55) between Brassica napus L. and 2x and 4x cabbage (B. oleracea var. capitata L.) was studied. The oleracea genome from B. napus maintained close homology with the c genome of cabbage while the campestris genome of B. napus showed partial homology with the c genome contained in the hybrids. Genotypic influence on chromosome pairing was indicated. Structural chromosome differences and spontaneous chromosome breakage and reunion were suggested as causes for the abnormalities which related to the unbalance of the genotypes. The divergence of the genomes of B. napus and B. oleracea and the need for the qualification of the term secondary association were discussed.Contribution No. J. 673, Research Station, Agriculture Canada, St. Jean, Québec.     

The transfer of triazine resistance from Brassica napus L. to B. oleracea L. I. Production of F1 hybrids through embryo rescue

Summary Triazine resistant Brassica napus ssp. oleifera and ssp. rapifera were hybridized to cultivars of B. oleracea ssp. italica, ssp. botrytis, ssp. capitata and ssp. fimbriata. The interspecific embryos did not survive in vivo but could be rescued in vitro using a culture medium developed by Monnier (1973). The embryos did not grow directly into normal plants but were successfully regenerated using the protocol developed by Keller (1984). Hybridization efficiency ranged from 0 to 2.64 hybrids per pollination. Interspecific embryo abortion may be related to abnormal endosperm development.