Glucosinolates and other seed quality traits of resynthesized Brassica napus L. derived from domesticated and wild Brassica taxa

Resynthesized Brassica napus L. genotypes can be used to increase the variation in the rapeseed genepool. We evaluated seed quality parameters of resynthesized lines that originated from crosses of oilseed B. rapa L. with domesticated (vegetable) B. oleracea L., and resynthesized lines that were obtained from crosses of B. rapa oilseed cultivars with wild B. oleracea ssp. oleracea and with seven Brassica species from the B. oleracea group (B. bourgeaui Kuntze, B. cretica Lam., B. incana Ten., B. hilarionis Post, B. montana Pourret, B. rupestris Raf., B. villosa Bivona-Bernardi). Twenty-three resynthesized lines and ten cultivars were grown in 1 year and six locations in Germany and the United Kingdom. The mean seed oil, phytosterole, and sinapine contents of the resynthesized lines were lower than in the cultivars, while protein, glucosinolate, and erucic acid contents were higher, respectively. Nearly all resynthesized lines derived from wild Brassica taxa showed a glucosinolate pattern very different from all cultivars and from nearly all resynthesized lines obtained from crosses with domesticated B. oleracea. The newly developed wild Brassica based resynthesized lines represent an immense source of genetic variation that has not been used to full capacity up to now.     

Extending the rapeseed genepool with resynthesized Brassica napus L. I: Genetic diversity

Resynthesized Brassica napus L. could be employed to increase the genetic variation in the narrow oilseed rape genepool and to establish a genetically distant genepool for hybrid breeding. One important criterion for selecting appropriate resynthesized lines is their genetic distance to adapted breeding material. In this study we estimated the genetic distances in a wide collection of 142 resynthesized lines and 57 winter and spring rapeseed cultivars from Europe, North America and Asia using RFLP marker data. The highest in-group genetic distance (0.36) was observed in 142 resynthesized lines compared to 0.21 in winter, 0.23 in summer, and 0.28 in Asian genotypes. The group of adapted breeding material clustered into three groups of winter-, spring-type, and Asian genotypes. Resynthesized lines did not form distinct subgroups in the cluster analysis, but large differences were revealed in the genetic distance of resynthesized lines to the adapted winter oilseed rape genepool. The highest distance to winter oilseed rape was found in resynthesized lines with parental lines from the Asian genepool as B. oleracea convar. botrytis var. alboglabra (Bail.) Sun or B. rapa ssp. chinensis (L.) Hanelt.     

Expression and inheritance of isozymes in Brassica species and in their interspecific hybrids

Abstract

Gene expression was analysed by means of isozyme electrophoresis for three diploid species Brassica rapa (genome AA), B. nigra (BB), and B. oleracea/ B. oleracea var. alboglabra (CC), three amphidiploids B. juncea (AABB), B. napus (AACC) and B. carinata (BBCC), and in 15 interspecific hybrids from crosses within and between the diploids and the amphidiploids. Five enzyme systems were assessed: glucosephosphate isomerase, leucine aminopeptidase, phosphoglucomutase, 6-phosphogluconate dehydrogenase and malate dehydrogenase. Alleles descending from the diploid species were found both in natural and artificially produced amphidiploids. No effect of reciprocal crosses was observed. i.e., the Brassica isozymes were under nuclear gene control. Mendelian segregation in the F₂ generation from crossing two resynthesized B. napus was observed for the loci glucosephosphate isomerase-2 and phosphoglucomutase-3. Genome-specific alleles were identified for several loci. No alteration in the allelic expression of isozymes was found when assembling all three Brassica genomes in the trigenomic interspecific hybrids. Moreover, trigenomic hybrids were capable of disclosing a silent allele of leucine aminopeptidase from B. carinata, and thus in this study the capability of isozyme analysis for detecting hidden variation was demonstrated.     

Organically grown Brassica napus – use of border strips and Trichoderma

Oilseed rape (Brassica napus L.) is a very difficult crop to cultivate organically. Only few organic methods are effective in reducing damage from insects and diseases. The current investigation assessed the use of the beneficial ascomycete Trichoderma asperellum (Samuels, Lieckf & Nirenberg) and a trap crop of Brassica rapa L. turnip rape cv. “Brachina,” both with and without an application of slurry fertilizer, for pest suppression and yield enhancement of winter oilseed rape cv. “Californium.” The presence of the trap crop significantly increased 1000 grain weight but not total yield or lipid content of the oilseed rape because turnip rape was not attractive enough to prevent colonization of the principal crop. Increase in 1000 grain weight, lipid content, and total seed yield were found in oilseed rape sprayed with three applications of T. asperellum, but the ascomycete had no influence on the insect pests observed. The effects of the fertilizer are about equal to the effects of the fungus on 1000 grain weight and on lipid content.     

Analysis of Genetic Diversity in the Brassica napus L. Gene Pool Using SSR Markers

Genetic diversity throughout the rapeseed (Brassica napus ssp. napus) primary gene pool was examined by obtaining detailed molecular genetic information at simple sequence repeat (SSR) loci for a broad range of winter and spring oilseed, fodder and leaf rape gene bank accessions. The plant material investigated was selected from a preliminary B. napus core collection developed from European gene bank material, and was intended to cover as broadly as possible the diversity present in the species, excluding swedes (B. napus ssp. napobrassica (L.) Hanelt). A set of 96 genotypes was characterised using publicly available mapped SSR markers spread over the B. napus genome. Allelic information from 30 SSR primer combinations amplifying 220 alleles at 51 polymorphic loci provided unique genetic fingerprints for all genotypes. UPGMA clustering enabled identification of four general groups with increasing genetic diversity as follows (1) spring oilseed and fodder; (2) winter oilseed; (3) winter fodder; (4) vegetable genotypes. The most extreme allelic variation was observed in a spring kale from the United Kingdom and a Japanese spring vegetable genotype, and two winter rape accessions from Korea and Japan, respectively. Unexpectedly the next most distinct genotypes were two old winter oilseed varieties from Germany and Ukraine, respectively. A number of other accessions were also found to be genetically distinct from the other material of the same type. The molecular genetic information gained enables the identification of untapped genetic variability for rapeseed breeding and is potentially interesting with respect to increasing heterosis in oilseed rape hybrids.     

Introgression between oilseed rape (Brassica napus L.) and its weedy relative B. rapa L. in a natural population

We investigated introgression in a mixed weedy population ofoilseed rape (Brassica napus) and itsrelative B. rapa usingspecies-specific AFLP-markers. The population wassituated in a field relayed from conventional to organic cultivation11 years ago. One-hundred-and-twoB. napus orB. rapa-like plantswere collected in a 3 m² plot. Of these, onewas a first generation hybrid (F₁) and nearlyhalf (44 plants) were introgressed, having bothB. napus andB. rapa specific markers.The remaining plants apparently corresponded to pure species, with 50having only B. rapa-and seven having only B.napus-specific markers. We compared thenumber of markers in the plants from the weedy population with thenumbers in controlled backcross generations (BC₁ andBC₂). The marker distribution in the weedy populationresembled the distribution in the second backcross generation mostclosely. Together with the cultivation history of the field, thissuggests that the introgression process in the weedy mixed populationhas been in progress for some time. This study is the first to showintrogression between B.napus and B.rapa under natural conditions.     

Cytoplasmic diversity of Brassica napus L., Brassica oleracea L. and Brassica rapa L. as determined by chloroplast microsatellite markers

Cytoplasmic genomes in most angiosperms are known to be maternally inherited. Oilseed rape (Brassica napus L.) as a natural amphidiploid species hence may carry the B. oleracea L. or the B. rapa L. cytoplasm, depending on the cross direction. The presence of either the B. oleracea or the B. rapa cytoplasm in oilseed rape has been reported to affect agronomically important traits. However, to date little is known about the cytoplasmic composition and genetic diversity of current winter oilseed rape cultivars and breeding material. The aim of this study was to assess the usefulness of 40 previously published chloroplast cpSSR markers from Brassica species and Arabidopsis thaliana (L.) Heynh. for distinguishing the cytoplasms of 49 different genotypes of B. napus and its diploid ancestor species. Results showed that only 14 out of the 40 tested primer combinations were suitable to distinguish the cytoplasms of a test set of 8 Brassica genotypes. With the 14 primer pairs 64 different cpSSR alleles were identified in the set of 49 genotypes. Cluster analysis indicated distinct groups for the cytoplasms of B. napus, B. rapa, and B. oleracea. However, an unambiguous identification and classification of the cytoplasm types was not possible in all cases with the available polymorphic set of cpSSR primer pairs.     

Boron nutrition for improving the quality of diverse canola cultivars

Abstract

Canola (Brassica napus L.), is the most important oilseed crop due to high oil contents and low concentration of erucic acid and glucosinolates. In Pakistan, oil seed production is not sufficient to fulfill the needs of the country. Thus, the planned experiment was aimed to evaluate the performance of different canola cultivars i.e. Faisal Canola, Pakola, PARC Canola hybrid and Rainbow at grown under various soil applied boron (B) levels viz., 0, 1, 2?kg ha^?1 under a rainfed environment. The experiment was laid out in randomized complete block design with four replications. Among the canola cultivars, the maximum seed oil contents were recorded in cultivar ‘Pakola’ whereas, higher linolenic acid and protein were recorded in cultivar ‘Faisal canola’ as compared to other cultivars. A synergistic effect was found between various levels of B and quality parameters of the canola seed; as higher concentration of oil contents were found when B was applied 2?kg ha^?1. Conversely the linolenic acid showed the antagonistic behavior with the various B levels. On the other hand, protein contents, oleic acid and erucic acid revealed non-significant differences under different B application rates. In conclusion, the cultivar ‘Pakola’ provided the highest oil content when the B was applied at 2?kg ha^?1; the low concentration of unsaturated fatty acid was observed in ‘PARC canola’ cultivar in the Pothwar region of Punjab, Pakistan.     

Characterization of fertile amphidiploid between <Emphasis Type="Italic">Raphanus sativus</Emphasis> and <Emphasis Type="Italic">Brassica alboglabra</Emphasis> and the crossability with <Emphasis Type="Italic">Brassica</Emphasis> species

A fertile amphidiploid × Brassicoraphanus (RRCC, 2n = 36) between Raphanus sativus cv. HQ-04 (2n = 18, RR) and Brassica alboglabra Bailey (2n = 18, CC) was synthesized and successive selections for seed fertility were made from F₄ to F₁₀. F₁₀ plants exhibited good fertility with 14.9 seeds per siliqua and 32.3 g seeds per plant. Cytological observation revealed that frequent secondary pairing occurred among 3 chromosome pairs in pollen mother cells of plants (F₄) with lower fertility, but not of plants with high fertility (F₁₀). GISH analysis indicated that these F₁₀ plants included the expected 18 chromosomes from R. sativus and B. alboglabra, respectively, but they lost approximately 27.6% R. sativus and 35.6% B. alboglabra AFLP (amplified fragment length polymorphism) bands. The crossability of the Raphanobrassica with R. sativus and 5 Brassica species (13 cultivars) were investigated. Seeds or F₁ seedlings were easy to be produced from crosses × Brassicoraphanus × R. sativus, and B. napus, B. juncea and B. carinata × Brassicoraphanus. Fewer seeds or seedlings were obtained from crosses × Brassicoraphanus × B. napus, B. juncea and B. carinata. However, few seeds were harvested in the reciprocals of × Brassicoraphanus with B. rapa and B. oleracea. The possible cause of fertility improvements and the potential of the present × Brassicoraphanus for breeding were discussed.     

Complete chloroplast genome sequence of rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) and its evolutionary implications

The complete nucleotide sequence of the rapeseed (Brassica napus L.) chloroplast genome (cpDNA) was determined. The 152,860 bp cpDNA contained a pair of 26,035 bp inverted repeat regions (IR), which are separated by small and large single copy regions (SSC and LSC) of 83,030 and 17,760 bp, respectively. The major portion (56.4%) of the B. napus cpDNA consists of gene coding regions, while intergenic spacers make up 43.6% of the complete genome. The average AT content of the B. napus cpDNA is 63.7% and for the LSC, SSC and IR region is 65.9, 70.8 and 57.7%, respectively. Fifteen genes contained one intron, while three genes had two introns. In total, 86 simple sequence repeats were identified. The detailed comparison of the B. napus with one of its putative parents, B. rapa L. cpDNA indicated that the two species were highly similar. The entire gene pool and relative positions of 113 individual genes were identical to those of B. rapa cpDNA. The sequence divergence analysis of B. napus and B. rapa showed only 0.133% in the coding regions, 0.275% in the intron regions, and 0.348% in the intergenic spacer regions. The phylogenies based on 61 protein coding genes from 48 cpDNA sequences provided strong support for monophyly of many major classes of angiosperms and provided support that Amborella could be a sister to all other angiosperms. Our analysis also supported that B. napus is the closest species to B. rapa and B. rapa could be the mathernal parent of B. napus cv. zy036.     

Potassium‐fertilizer management in winter oilseed‐rape production in China

Optimal potassium (K) fertilization is beneficial for oilseed‐rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseed‐rape production. A series of on‐farm experiments in the key winter oilseed‐rape domains of China was conducted from 2004 to 2010 to evaluate K‐fertilizer management for winter oilseed rape. Currently, the average NH₄OAc‐extractable K content in the 0–20 cm soil layer is 89.1 mg kg^–1 indicative of “slight deficiency”. In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed‐rape production, the average mineral‐potassium‐fertilizer input in 2010 being only 35 kg K ha^–1, far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yield‐increase rate for the major production regions due to K‐fertilizer application was 18.5%, and the average K fertilizer–use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil‐K‐test index was established for winter oilseed rape with a threshold value for NH₄OAc‐extractable soil K of 135 mg kg^–1. When available soil K‐content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K‐fertilizer management in winter oilseed‐rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K‐testing technology in order to maintain both seed yield and soil fertility.     

Correlation studies on oil content and fatty acid profile of some Cruciferous species

Mean individual fatty acid concentration among differentspecies of the family Cruciferae are not similar because of the presence ofdifferent kind of significant relationship among the individual fatty acids.Brassica napus L., Sinapis alba L.,Raphanus caudatus L.f. Raphanus sativusL. and B. nigra (L.) Koch arecomparatively low erucic acid (<40%) containing species. Crambeabyssinica Hochst. ex. R. E. Fries collections gave as high as 60%erucic acid. Low erucic acid concentration was found associated with thepresence of high level of palmitic and oleic acid concentrations. Erucic acidconcentrations were found varied within the range of 42 to 57% among thecollections of Brassica rapa L. and B.carinata A. Braun. All the collections ofB. nigra (L.) Koch were found to havehigher proportion of linoleic acid than the corresponding oleic acidconcentration. Linolenic acid concentrations of B.nigra (L.) Koch was also higher in comparison to otherspecies of the Cruciferae. Raphanus collections were foundto contain higher levels of total saturated fatty acids as well as eicosenoicacid. Oil content of the total collections under present study did not show anysignificant relationship either with linolenic acid or with erucic acidconcentration. But significant positive relationship was observed between totaloil and erucic acid level within the collections of B.juncea Czern. & Coss. Similarly significant negativecorrelation was observed between total oil and linolenic acid content inBrassica rapa L. ssp. trilocularis (Roxb.) Hanelt, yellow sarson.     

Revitalizing the winter turnip rape crop in the northern latitudes

Abstract

Winter turnip rape (Brassica rapa spp. oleifera) is an underutilized crop that deserves to be revitalized for use in high-latitude agriculture. Many crop rotations around the world are dependent on the small-grain cereals, and turnip rape as a break crop, with its range of secondary chemicals, helps to suppress weeds, nematodes and pathogenic fungi. It may be used as an energy crop, it can restrict erosion and nutrient leaching while also improving soil structure and fertility, and it requires relatively low inputs. Although winter turnip rape was once the major oil crop in Finland, in the 1970s it was replaced by spring turnip rape, the lower erucic acid and glucosinolate contents of which made it suitable for food and feed uses. Winter hardiness of the crop could be improved, and industrial end uses, such as lubricants for which high erucic acid content is preferred, targeted in the first instance. Breeding progress would be accelerated by a change from the predominantly self-incompatible breeding system to self-compatibility, now available in modern germplasm, and this would allow use of other rapid breeding methods, such as doubled haploidy. Thus, the many advantages of the winter turnip rape crop would repay its return to agriculture. In this review we will introduce the many utilization possibilities of the crop as well as give background on why more attention and research efforts should be paid towards this crop. We will also indicate some of the array of factors that have a marked role in an attempt to ecologically intensify crop production.     

Flea beetle (Chrysomelidae: Alticinae) species composition and abundance in different cruciferous oilseed crops and the potential for a trap crop system

Flea beetles are significant insect pests of cruciferous oilseed crops in northern Europe. A two-year small-scale field experiment was performed to determine the species complex and abundance of flea beetles (Chrysomelidae: Alticinae) associated with eight cruciferous oilseed plants: Brassica juncea (L.) Czern., Brassica napus L. var. oleifera subvar. annua, Brassica nigra (L.) Koch, Brassica rapa L. var. oleifera subvar. annua, Camelina sativa (L.) Crantz, Eruca sativa Mill., Raphanus sativus L. spp. oleifera (DC) Metzg. and Sinapis alba L. Their relative attractiveness to flea beetles was compared to assess their potential for use within a trap crop system for spring oilseed rape. Adults of six species of flea beetles were found on the test plants. Phyllotreta undulata Kutsch. was the most abundant species followed by Phyllotreta nigripes (Fabr.), Phyllotreta nemorum L. and Phyllotreta vittata (=striolata) (Fabr.), while Phyllotreta atra (Fabr.) and Chaetocnema concinna Marsh. were occasionally present. The species composition of flea beetles on seven of the investigated plant species was fairly similar but differed significantly on C. sativa. The flea beetle species discriminated between the tested host plants, with a general gradient in attraction from E. sativa > B. juncea > B. nigra > R. sativus > S. alba > B. rapa > B. napus through to C. sativa. Brassica juncea and B. nigra developed faster and at early growth stages were more attractive to overwintered adult flea beetles than B. napus and therefore had potential as trap plants to protect spring rape. R. sativus and E. sativa, despite their development rate being slower than B. napus were also more attractive to flea beetles. Thus, further experiments with a complex of attractive early season and late-season plant species (multiple trap crops) should be undertaken.     

氮、磷、钾、硼肥对甘蓝型油菜籽品质的影响

以多个正在大面积应用的甘蓝型油菜品种为研究对象,在长江流域冬油菜主产区的10个省（市）布置氮、磷、钾和硼肥田间肥效试验共284组,通过多点试验分别探讨当前生产条件下施用氮、磷、钾、硼肥对双低和双高甘蓝型油菜籽含油量、蛋白质、芥酸、硫甙的影响。结果表明,双低油菜籽平均含油量为41.66%,双高油菜含油量明显低于双低油菜,仅为38.92%。氮、磷、钾和硼肥施用对油菜籽的品质效应在不同试验点表现不尽相同,其总体趋势是:在磷、钾、硼肥基础上施用氮肥提高籽粒蛋白质含量而降低油分含量,且随氮肥用量的增加效果更明显,施氮对双高油菜油分及蛋白质含量的影响程度大于双低油菜;施磷、钾或硼肥有提高油菜籽含油量而降低蛋白质含量的趋势;施肥对油菜籽硫甙和芥酸含量有一定影响,但对品质影响不大。油菜籽含油量与收获指数、千粒重显著正相关,与蛋白质含量呈负相关。研究结果显示,在施氮的基础上配合施用磷、钾和硼肥能减少因施氮引起的油分损失。     

Identification of Phosphorous Efficient Germplasm in Oilseed Rape

ABSTRACT

Plant species and genotypes within one species may significantly differ in phosphorus (P) uptake and utilization when they suffer from P starvation. The objective of this research was to screen P-efficient germplasm of oilseed rape (Brassica napus L.) and analyze the possible mechanism responsible for P efficiency by two-steps screening experiments and validation of P efficiency. Phosphorus efficiency coefficient at seedling stage, namely, ratio of shoot dry weight under low P to that under adequate P (PECS) of 194 oilseed rape cultivars varied from 0.050 to 0.62 and was significantly related with shoot dry weight under low P level (r = 0.859??, P < 0.01). Oilseed rape cultivar ‘Eyou Changjia’ presented the highest P efficiency coefficient in each growth stage and had the highest seed yield at low P, whereas oilseed rape cultivar ‘B104-2’ was the most sensitive to low P stress among the 12 candidate cultivars obtained from the two-steps screening experiments. Under low P condition in validation experiments of soil and solution cultures, ‘Eyou Changjia’ could produce much more dry matter and acquire more P than ‘B104-2.’ Moreover, P efficient coefficient obtained from the pot experiment was comparable to those from the field experiment. This might be attributed to high P uptake efficiency for ‘Eyou Changjia’ when it suffered from low-P stress. Comparison of results from the hydroponics with those from the pot and field experiments led to the conclusion that the P uptake efficiency in the hydroponics is highly related to that in soil culture conditions. These results show that there are large genotypic differences in response to phosphorus deficiency in oilseed rape germplasm (Brassica napus L.) and ‘Eyou Changjia’ is P-efficient and ‘B104-2’ is P-inefficient. By comparing these results further, the mechanism responsible for P efficiency was suggested to be mainly due to high P uptake efficiency by forming larger root system, and improving the ability of mobilizing and acquiring soil P in P-efficient oilseed rape under the condition of P starvation.     

Effect of Root Zone Temperature on Oilseed Rape (Brassica napus) Response to Boron

Abstract

Oilseed rape (Brassica napus) is sensitive to low boron (B) supply, and its growth response to B may be influenced by soil temperature. To test the relationship between B and temperature, oilseed rape (cv. Hyola 42) seedlings were grown at 10°C (low) root zone temperature (RZT) with B supply from deficient to adequate B levels until growth of low B plants just began to slow down. Half of the pots were then transferred to 20°C (warm) RZT for 11 days before they were moved back to 10°C RZT for the final 4 days. Both plant dry mass and B uptake increased after plants were exposed to warm RZT. However, plant B deficiency was exacerbated by warm RZT in low B plants because of increased relative growth rate and shoot–root ratio without a commensurate increase in B uptake rate. It is concluded that RZT above the critical threshold for chilling injury in oilseed rape can nevertheless affect the incidence of B deficiency by altering shoot–root ratio and hence the balance between shoot B demand and B uptake.     

PHENOLOGY AND SEED QUALITY RESPONSE OF RAPE (B. NAPUS) VERSUS MUSTARD (B. JUNCEA) TO SULFUR AND POTASSIUM FERTILIZATION IN NORTHWEST PAKISTAN

Inappropriate sulfur and potassium fertilization, particularly with continued soil nutrient mining and yearly fluctuations in rainfall, are major factors contributing to slow growth and low seed quality of canola in northwestern Pakistan. A field experiment was conducted in 2007–2008 on a sulfur (S) and potassium (K) deficient clay loam soil under irrigation at the research farm of NWFP (Northwest Frontier Province) Agricultural University, Peshawar, Pakistan, with an objective to determine response of phenology and seed quality of Brassica oilseed rape versus mustard to S and K fertilizer application. Twenty treatments in a randomized complete block design were consisted of two oilseed genotypes [rape (B. napus canola) and mustard (B. juncea canola)], at three rates each of S (15, 30, and 45 kg S ha^?1) and K (30, 60, and 90 kg K ha^?1), plus control (no K and S applied). Days to flowering, pod formation, seed filling duration and maturity were enhanced with K and S fertilization compared to control plots. The species B. napus took more time to flowering, pod formation, seed filling duration and maturity compared to B. juncea. Both genotypes responded positively for seed quality (oil and protein content) to K and S fertilization, but the magnitude of response varied with level and combination of K and S fertilization. Delay in the phenological stages showed negative relationship with oil and protein content in seed of both genotypes. It is concluded that a combination of 60 kg K ha^?1 + 30 kg S ha^?1 would accelerate phenological development and improve seed quality of rape and mustard in the study area.     

Identification and overcoming barriers between Brassica rapa L. em. Metzg. and B. nigra (L.) Koch crosses for the resynthesis of B. juncea (L.) Czern.

Brassica juncea (2n = 36, AABB) is an amphidiploid derived from its diploid progenitor species B. rapa (2n = 20, AA) and B. nigra (2n = 16, BB). Resynthesis of B. juncea by exploiting the wider gene pool of the present day diploids offers a powerful tool for obtaining novel genetic variation. Hybridization between the two species is difficult because of the presence of crossability barriers. Barriers to hybridization were identified using Aniline Blue Fluorescence (ABF) method. Crosses were classified as having pre- or post-fertilization barriers based on whether less than or more than one per cent ovules showed pollen tube entry. Of the 23 crosses studied, seven crosses all with B. rapa as the female parent showed pre-fertilization barriers. Only 0 to 0.3 per cent ovules were fertilized in these crosses. The remaining 16 crosses, four with B. rapa as the female parent and 12 with B. nigra as the female parent, showed post-fertilization barriers. In crosses with pre-fertilization barriers use of bud pollination and stump pollination ensured or increased fertilization. These two simple techniques were used in combination with ovary-ovule culture to ensure recovery of hybrids. In crosses with post-fertilization barriers, ovary-ovule culture alone helped to obtain hybrids. Hybrids were obtained at higher frequency with the use of direct ovule culture compared to ovary-ovule culture. The F₁ plants obtained in vitro were multiplied on MS medium + 2 mg/l Kn + 0.2 mg/l IAA. These F₁ plants were confirmed as true hybrids through morphology, leaf isozymes and cytology. In all 17 hybrids were obtained of which three were amphidiploids.     

Sowing date influence on winter oilseed rape overwintering in Estonia

Abstract

In 2001–2005 an overwintering investigation of winter oilseed rape (Brassica napus L.) was carried out at the Institute of Agricultural and Environmental Sciences of the Estonian University of Life Sciences. In our trial we used two winter oilseed rape varieties: ‘Wotan’ and ‘Express’. The sowing was performed at four different times, with weekly intervals: 8, 15, 22 and 29 August. The soil type was Stagnic Luvisol by WRB classification; the texture was sandy loam with a humus layer of 20–30 cm. Our research indicated that successful wintering of winter oilseed rape depends directly on sowing date. From the data obtained it may be seen that differences between sowing dates and overwintering were statistically significant. Overwintering depends on numbers of growing-degree-days (GDD) in the autumn vegetative period. Three years’ data showed that in the autumn period plants need 416 GDD for developing a strong root system and to prepare for wintering.