Effects of Nitrogen Fertilizer Management on Biological Traits and Physiological Indexes at Seedling Stage and Yield of Directly-sown Rapeseed(Brassica napus L.)

Field experiments were carried out to study the effects of different nitroge- napplication rates and application times on biological traits and physiological indexes of directly-sown rapeseed （Brassica napus L.） at the seedling stage and investigate the relationship between these biological traits or physiological indexes at the seedling stage and yield, so as to provide scientific theoretical support for high yield and efficient fertilization management in production of winter rapeseed. Field trials were conducted in Chengdu plain of Sichuan Province under rice-rapeseed rotation system during the period of 2011-2012. The nitrogen application rate trial consisted of five nitrogen levels （0, 90, 180, 270 and 360 kg/hm2） and the nitrogen application time trial included NTl（single application as base fertilized）, NT2 （bottom application ＋one time of topdressing at seedling stage） and NT3 （bottom application＋two times of topdressing at seedling stage） under the same nitrogen rate （225 kg/hm2）. The results indicated that compared with no nitrogen application （NO） treatment, the in- crease of nitrogen fertilizer is beneficial to the increase of biological traits including plant height, green leaf number, leaf area index and dry weight of rapeseed at the seedling stage, the improvement of physiological indexes including total nitrogen content, chlorophyll content and soluble protein content of functional leaves, and the reduction of soluble sugar content. Nitrogen rate was linearly correlated with various biological traits at the seedling stage and physiological indexes including total nitro- gen content, chlorophyll content and soluble sugar content in functional leaves over- a/I, but in parabolic correlation with soluble protein content. Under the same nitrogen rate, NT2 treatment exhibited biological traits remarkably or significantly higher than NT1 treatment and NT3 treatment. The nitrogen application times were linearly cor- related with the physiological indexes of functional leaves at the seedling stage. The various biological traits and physiological index of functional leaves at the seedlings stage were in quadratic function parabolic correlation with seed yield, and the corre- lation was significant （P〈0.05）. Therefore, under the rice-rapeseed rotation system in Chengdu plain, the economic rational nitrogen rate is 180-225 kg/hm2, and the mode of bottom application ＋ one time of topdressing （NT2） is suitable.

The influence of Lactobacillus plantarum fermentation in selenium-enriched Brassica napus L.:changes in the nutritional constituents,bioactivities and bioaccessibility

Selenium(Se)-enriched Brassica napus L.is a valuable organic Se supplement.In this study,the fermentation broth enriched with organic Se(FFS)was prepared using Lactobacillus plantarum to ferment the substrate of Se-enriched Brassica napus L.Significant increases were observed after fermentation in total sugars,reducing sugars,soluble proteins,total phenolic content(TPC),and total flavonoid content(TFC).The organic Se was retained at a concentration of 54.75 mg/g in the freeze-dried sample.Principal component analysis and cluster analysis showed good separation between the FFS and unfermented(FS)groups.Fragrant 2-ethyloxetane had the highest content among all volatiles,while sinapine had the highest content among all phenolic compounds.The fermentation process showed remarkable improvement in the abundance and concentration of volatile compounds and phenolic contents,making FFS exhibit strong antioxidant activity and inhibitory capacity againstα-glucosidase activity.The bioaccessibility of phenolic compounds was significantly greater in FFS compared to FS.ADMET analysis revealed that the majority of phenolic compounds contained in FFS did not exhibit mutagenicity toxicity,hepatotoxicity,skin sensitization,or blood-brain barrier penetration,indicating a favorable level of biosafety.Overall,our study provides a new insight into the further utilization of Se-enriched Brassica napus L.in foods.

Effect of Foliar Fertilizer Spraying at Seedling Stage on the Growth Physiological Characteristics and Yield of Brassica napus L.

In order to select a suitable foliar fertilizer for Brassica napus L.at the seedling stage,using‘Fengyou 958’as the material,different foliar fertilizers including BR,Se,Si,BR+Si,BR+Se,Se+Si and BR+Se+Si were sprayed at the seedling stage to study their effect on the physiological characteristics,growth and yield of Brassica napus L..The results showed that the growth,chlorophyll content,soluble sugar content,soluble protein content,and yield of different treatments at the budding stage improved compared with the control.The effect of the Si+Se treatment was the best,followed by the Se and Si treatments.The chlorophyll content of the flower decreased continuously during the whole flowering period,and the chlorophyll content of the mature silique peel was higher than that of the seed.The content of soluble sugar in flowers was the highest in the early flowering stage,and the content of soluble sugar in leaves at the flowering stage was higher than that at the budding stage.The soluble sugar content in the harvested silique peel decreased gradually with the increase of time,and that in the silique peel and seed was similar at 35 d after pollination.The soluble protein content in the silique peel and seed decreased gradually at the mature stage,and the soluble protein content in the silique peel was higher than that in the seed at the same stage.Si+Se foliar fertilizer spraying at the seedling stage can promote the growth and yield of Brassica napus L.and can be applied in Brassica napus L.production.

Development of a KASP Marker on Chromosome A05 for Seed Oil Content of Brassica napus

In order to identify the molecular markers that can be widely used in the breeding of Brassica napus L.varieties with high seed oil content under different genetic backgrounds,we developed a Kompetitive Allele Specific PCR(KASP)marker for seed oil content on the basis of the results from available studies.The verification in the F_(2) population showed that the marker was closely linked to the quantitative trait locus(QTL)for oil content on chromosome A05.The findings helped to breed the‘Fengyou’varieties with high seed oil content in the middle reaches of the Yangtze River.

Comparions of Required Nitrogen Fertilizers by Hybrid Cultivar and Conventional Cultivar of Rapeseed(Brassica napus L.)

[Objective] The aim of this study was to understand the difference of N fertilizer requirement between hybrid rapeseed and conventional rapeseed. [Method] Two hybrid cultivars, ZY5628 and ZY7819, and the conventional cultivar ZS10, were compared through two field experiments. In Experiment 1, seed yield and optimum N application rate were assessed in the field with five N application treatments. In Expedment 2, N was applied uniformly at 180 kg/hm2, and plant biomass and N accumulation were measured at several developmental stages, while N use efficien- cy was calculated for rape at maturity. [Results] The experiment 1 results showed that seed yields of ZY5628 and ZY7819 were both significantly higher than that of ZS10, and compared to ZS10, optimum yield （plateau yield） was higher by 18.7% and 20.2%, while the recommended N application rate was lower by 9.5% and 9.6% for ZY5628 and ZY7819, respectively. The experiment 2 results showed that during vegetative development, all three cultivars exhibited similar accumulations of plant biomass and N, but through flowering and maturity ZY5628 and ZY7819 pro- duced more biomass, acquired more N, and utilized acquired N more efficiently to- wards seed production than ZS10. [Conclusion] With equivalent inputs, the hybrid rapeseed cultivars ZY5628 and ZY7819 tested herein yield more seed with higher N use efficiency than the conventional rapeseed ZS10. This information will be valu- able for growers seeking to improve efficiency while reducing costs of rape production in China.

Identification of suitable reference genes in leaves and roots of rapeseed (Brassica napus L.) under different nutrient deficiencies

Nutrient deficiency stresses often occur simultaneously in soil. Thus, it＇s necessary to investigate the mechanisms underlying plant responses to multiple stresses through identification of some key stress-responsive genes. Quantitative real-time PCR （qRT-PCR） is essential for detecting the expression of the interested genes, of which the selection of suitable reference genes is a crucial step before qRT-PCR. To date, reliable reference genes to normalize qRT-PCR data under different nutrient deficiencies have not been reported in plants. In this study, expression of ten candidate reference genes was detected in leaves and roots of rapeseed （Brassica napus L.） after implementing different nutrient deficiencies for 14 days. These candidate genes, included two traditionally used reference genes and eight genes selected from an RNA- Seq dataset. Two software packages （GeNorm, NormFinder） were employed to evaluate candidate gene stability. Results showed that VHA-E1 was the highest-ranked gene in leaves of nutrient-deficient rapeseed, while VHA-G1 and UBC21 were most stable in nutrient-deficient roots. When rapeseed leaves and roots were combined, UBC21, HTB1, VHA-G1 and A CT7 were most stable among all samples. To evaluate the stabilities of the highest-ranked genes, the relative expression of two target genes, BnTrxl;1 and BnPhtl;3 Were further determined. The results showed that the relative expression of BnTrxl;1 depended on reference gene selection, suggesting that it＇s necessary to evaluate the stability of reference gene prior to qRT-PCR. This study provides suitable reference genes for gene expression analysis of rapeseed responses to different nutrient deficiencies, which is essential for elucidation of mechanisms underlying rapeseed responses to multiple nutrient deficiency stresses

Recent Advances,Problems and Outlooks in Rapeseed(Brassica napus L.)Breeding in China

As a big rapeseed （Brassica napus L.） producing and consuming country, China provides more and more rapeseea oil year by year. With the development of demand for rapeseed and import of edible oil, rapeseed breeding and production is fac- ing a great challenge. New situation has proposed higher requirements to yield, oil quality and safety, etc. In the review, some aspects about rapeseed breeding in China were reported, including breeding of high-oil content rapeseed, breeding of extremely early-maturing rapeseed, development of mechanization and development of chemical emasculation. Some prospects and expec- tations were also proposed.

Physiological and molecular responses to cold stress in rapeseed(Brassica napus L.)

Low temperature is one of the most important abiotic factors inhibiting growth, productivity, and distribution of rapeseed(Brassica napus L.). Therefore, it is important to identify and cultivate cold-tolerant germplasm. The objective of this study was to figure out the mechanism of chilling(4 and 2°C) and freezing(–2 and –4°C) stresses along with a control(22°C) in B. napus cultivars(1801 and C20) under controlled environment(growth chamber). The experiment was arranged in a complete randomized design with three replications. Our results exhibited that under chilling and freezing stresses, the increment of proline accumulation, soluble sugar and protein contents, and antioxidant enzyme activity were enhanced more in 1801 cultivar compared with C20 cultivar. At –2 and –4°C, the seedlings of C20 cultivar died completely compared with 1801 cultivar. Hydrogen peroxide(H2 O2) and malondialdehyde contents(MDA) increased in both cultivars, but when the temperature was decreased up to –2 and –4°C, the MDA and H2 O2 contents continuously dropped in 1801 cultivar. Moreover, we found that leaf abscisic acid(ABA) was enhanced in 1801 cultivar under chilling and freezing stresses. Additionally, the transcriptional regulations of cold-tolerant genes(COLD1, CBF4, COR6.6, COR15, and COR25) were also determined using real-time quantitative PCR(RT-q PCR). RT-q PCR showed that higher expression of these genes were found in 1801 as compared to C20 under cold stress(chilling and freezing stresses). Therefore, it is concluded from this experiment that 1801 cultivar has a higher ability to respond to cold stress(chilling and freezing stresses) by maintaining hormonal, antioxidative, and osmotic activity along with gene transcription process than C20. The result of this study will provide a solid foundation for understanding physiological and molecular mechanisms of cold stress signaling in rapeseed(B. napus).

Exogenous application of a low concentration of melatonin enhances salt tolerance in rapeseed(Brassica napus L.) seedlings

Melatonin is a naturally occurring compound in plants. Here, we tested the effect of exogenous melatonin on rapeseed（Brassica napus L.） grown under salt stress. Application of 30 μmol L^-1 melatonin alleviated salt-induced growth inhibition, and the shoot fresh weight, the shoot dry weight, the root fresh weight, and the root dry weight of seedlings treated with exogenous melatonin increased by 128.2, 142.9, 122.2, and 124.2%, respectively, compared to those under salt stress. In addition, several physiological parameters were evaluated. The activities of antioxidant enzymes including peroxidase（POD）, catalase（CAT） and ascorbate peroxidase（APX） were enhanced by 16.5, 19.3, and 14.2% compared to their activities in plants without exogenous melatonin application under salt stress, while the H2O2 content was decreased by 11.2% by exogenous melatonin. Furthermore, melatonin treatment promoted solute accumulation by increasing the contents of proline（26.8%）, soluble sugars（15.1%） and proteins（58.8%）. The results also suggested that higher concentrations（〉50 μmol L^-1） of melatonin could attenuate or even prevent the beneficial effects on seedling development. In conclusion, application of a low concentration of exogenous melatonin to rapeseed plants under salt stress can improve the H2O2-scavenging capacity by enhancing the activities of antioxidant enzymes such as POD, CAT and APX, and can also alleviate osmotic stress by promoting the accumulation of osmoregulatory substances such as soluble proteins, proline, and water soluble glucan. Ultimately, exogenous melatonin facilitates root development and improves the biomass of rapeseed seedlings grown under salt stress, thereby effectively alleviating the damage of salt stress in rapeseed seedlings.

Molecular evidence for blocking erucic acid synthesis in rapeseed(Brassica napus L.) by a two-base-pair deletion in FAE1(fatty acid elongase 1)

DNA sequences of fatty acid elongase 1 genes FAE1.1 （EA） and FAE1.2 （Ec） were isolated and characterized for 30 com- mercialized low erucic acid rapeseed （LEAR） cultivars in China. Four types of independent mutation leading to low erucic acid trait were found, i.e., a single-base transition （eAl）, a two-base deletion （ec2） and four-base deletion （eC4） as well as single-base transition with a four-base deletion （eA.）. Three genotypes, i.e., eA1eA1eC2eC2, eA1eA1eC4eC4 and eA.eA.ec4ec4 were responsible for LEA content in storage Iipids of different rapeseed cultivars. Most of the LEAR cultivars had a genotype of eA1eA1ec2ec2, which were descended from the first LEAR cultivar, Oro. Yeast expression analysis revealed that two-base-pair （AA） deletion （ec2） at the base sites of 1 422-1 423 in the C genome FAE1 gene resulted in the absence of the condensing enzyme and led to the failure to produce erucic acid. Coexpression of FAE1 and ketoacyI-CoA reductase （KCR） or enoyI-CoA reductase （ECR） was found in high erucic acid rapeseed （HEAR） but not in LEAR （eA1eA1ec2ec2oreA1eA1ec4ec4）. Moreover, KCR and ECR were still coordinately regulated in eA1eA1ec2ec2 or eA1eA1ec4ec4 genotypes, suggesting that the expression of two genes was tightly linked. In addition, specific detection methods were developed by high-resolution melting curve analysis in order to detect eA1 and ec4.

Genetic Diversity of Chinese and Swedish Rapeseed (Brassica napus L.) Analyzed by Inter-Simple Sequence Repeats (ISSRs)

We have compared genetic diversity of 24 Chinese weak-winter, Swedish winter and spring B. napus accessions by inter-simple sequence repeats (ISSRs). By cluster analysis (UPGMA) based on 125 polymorphism bands amplified with 20 primers, the 24 accessions were divided into three groups. Six Swedish winter lines and eight Chinese weak-winter lines were in the group I and the groupⅡwere two Chinese weak-winter lines XiangyoulS and Bao81. The third group contained eight Swedish spring lines. Principal co-ordinates analysis (PCO) showed similar groupings to cluster analysis. Results from cluster analysis and PCO analysis showed very clearly that Chinese weak-winter, Swedish spring and winter accessions were distinguished from each other and Chinese weak-winter accessions in this study were genetically closer to Swedish winter accessions than to Swedish spring accessions. The Chinese weak-winter accessions had larger diversity than Swedish spring or winter accessions did. This study indicated that ISSR is a suitable and effective tool to evaluate genetic diversity among rapeseed germplasm.

Relationship Among Yield Components and Selection Criteria for Yield Improvement in Early Rapeseed (Brassica napus L.)

The objective of this study was to determine the relationship between seed yield and other important agronomic traits of early-maturing rapeseed as a rotation crop in a double-cropping rice area using Pearson＇s correlation coefficient as well as to estimate direct and indirect effects of specific yield component traits on seed yield via path analysis. Nineteen rapeseed genotypes were grown at ten environments in South China during 2008-2009 and 12 characters were evaluated. Analysis of variance showed that environment had a significant impact on all characters. For most characters the genotype by environment interaction was weak and not statistically significant. Simple correlation analysis indicated that the number of primary branches （PB）, number of pods on the main raceme （PR）, and number of seeds per pod made significant contributions to seed yield per plant （SYP）, while 1 000-seed weight was negatively correlated with SYP （r=-0.485, P0.05）. Furthermore, number of pods per plant （PP）, PB, and PR had the greatest direct effects on SYP. In addition, PP and PB were the best indicators to predict seed yield in stepwise regression analysis. Finally, yield component differences between early- and medium-maturity varieties were compared; this showed that to improve the seed yield of early varieties, more emphasis should be given to increase PP, PB, and PR, and reduce plant height and shortening of growth duration in breeding practice.

Heterosis for Seed Yield, Oil Content and Other Characters in Rapeseed (Brassica napus L.)

Nine inbred lines of rapeseed （Brassica napus L.） used as male were crossed to five recessive genetic male sterile （RGMS） lines used as female to produce 45 single crosses. The crosses, their parents and a check hybrid were tested at two locations during 2007 to 2008 for testing the performance and heterosis of hybrids for seed yield and other characters. Results showed that variations for seed yield, oil content, days to flowering and days to maturity were significant. Mean squares for hybrids were significant for all characters. High heterosis （-4.5%-88.3%）, heterobeltiosis （-15.6%-81.1%） and standard heterosis G34.8%-33.1%） were found for the seed yield. The highest heterosis and heterobeltiosis were found in the cross QH303-4A× 1190. The highest standard heterosis was found in the cross Qianyou8A×Q034. Both positive and negative heterosis of single crosses were detected for the oil content. Small heterosis was found for days to flowering and days to maturity. Among parents, Ⅲ 188, Ⅲ224, and Q034 were proved to be the superior for seed yield when used as parents in most of the hybrid combinations. 2365, Ⅲ224, and QH303-4AB were good for high oil content breeding, Ⅲ 176, 2313 and Qianyou3AB were good for the early hybrid breeding. Total 11 hybrids yielded higher than 2 500 kg·hm^-2 and also gave significantly positive heterosis, heterobeltiosis and standard heterosis. Among them, 10 crosses gave higher oil content than that of check. These crosses can be used in the future breeding program for the seed yield and the oil content. Two crosses including Qianyou3A × Ⅲ224 and Qianyou3A×2313 can be used for the early breeding program.

Genetic Diversity of Testa Pigments and RAPD Marker of Yellow-Seeded Rapeseed (Brassica napus L.)

14 yellow-seeded rapeseed lines (Brassia napus L.) from different genetic sources were used to analyze diversity of testa pigments content, oil and protein content, and RAPD markers. The results showed that the anthocyanin and melanin were the most important pigments in testa and their content were responsible for the variation in seed color ranging from orange to black yellow, 14 yellow-seeded lines could be classified into 3 groups: high anthocyanin content group with anthocyanin content over 2. 54 mg g-1 DW, the seed color was light yellow or orange; low pigments content group with low content of anthocyanin and melanin, the testa was transparent and the seed color was light yellow, greenish yellow or twany; high melanin content group with melanin content over 178. 4U(A290nm) , the testa was black, the seed color was black yellow. Oil content changed from 36.2% to 45. 5%, protein content from 21.1% to 27.7% , and the correlation analysis revealed that the oil content is highly significantly negatively correlated with the protein content. The cluster analysis showed that the extensive genetic variation existed among 14 yellow-seeded lines by using unweighted paired group method with arithmetic average (UPGMA) based on RAPD markers which were amplified with decamer primers, the genetic similarity among them ranged from 0. 25 to 0.909, and 14 yellow-seeded lines could put into 2 clusters corresponding to genome difference.

Inheritance of Erucic Acid,Glucosinolate,and Oleic Acid Contents in Rapeseed (Brassica napus L.)

This study was conducted to verify the inheritance of certain characters of rapeseed including erucic acid, glucosinolate and oleic acid contents by using generation mean analysis. The cross of lines Ⅲ174×Zi20 （F1）, F2, BC1 （F1×P1）, BC2 （F1×P2）, and parents （P1 and P2） were evaluated in the field. Data were measured on individual plants for oleic acid, erucic acid, and glucosinolate contents. Transgressive variations in F2 population were observed for oleic acid content, indicating that dominance and recessive genes distributed in both parents. Scaling test indicated that the effects of genes controlling these characters did not follow the additivedominance model. The data for three characters were analyzed using six parameter models and found that one or more types of epistatic gene effects were important for glucosinolate content. High broad sense heritabilities were obtained for erucic acid, oleic acid, and glucosinolate contents with the values of 98.97%, 93.68%, and 86.17%, respectively. Two major gene pairs were found to control the expression of erucic acid and oleic acid contents, while three major gene pairs were detected to control glucosinolate content.

Physiological and anatomical changes in two rapeseed (Brassica napus L.) genotypes under drought stress conditions

Understanding the mechanisms of drought resistance in crop species is crucial for the selection and breeding of tolerant rapeseed(Brassica napus L.)varieties.The present study aimed to assess the physiological and anatomical responses of two rapeseed genotypes,P287(drought-tolerant)and T88(drought-sensitive)under three intensities of drought stress.All physiological and anatomical parameters related to drought acclimation were significantly altered in both genotypes under stress conditions.At the fourth-leaf stage,the relative water content,chlorophyll content,protein content,malondialdehyde content,and the activities of peroxidase and catalase in P287 were significantly higher than those in T88,particularly under severe drought conditions.After rehydration,all physiological indexes recovered rapidly,especially in P287.In addition,under drought stress,compared with T88,P287 had thicker palisade tissue,thinner spongy tissue,higher ratio of chloroplast length to chloroplast width,higher stomatal density and stomatal closure rate.Overall,the interaction between physiological and anatomical features improved the drought tolerance of P287 under drought stress conditions.

Correlation Analysis on Male Sterile Lines Characters in Rapeseed(Brassica napus L.)

[Objective] This study was conducted to evaluate the associations of many characters of male sterile lines in Brassica napus L.[Method]10 recessive genetic male sterile（RGMS）lines were used as parents to cross in a half diallel cross method to produce 45 single cross hybrids.These 45 crosses and their 10 parents were evaluated at Guiyang during 2007-2008.[Result]The positive correlations of seed yield with plant height,pods per plant,days to flowering and days to maturity were significant.Their respective correlation coefficients（r）were 0.644,0.583,0.281 and 0.341.Highly significant and negative correlation was observed between seeds per pod and seed size（-0.533）.Direct path coefficients were observed for pods per plant（0.556 2）,seeds per pod（0.407 4）,1 000-seed weight（0.481 3）,and plant height（0.401 7）to seed yield.[Conclusion]Pods per plant,seeds per pod,1 000-seed weight and plant height were positive correlated with seed yield and showed high direct contributions to yield.Other characters including branches per plant,days to flowering,days to maturity and oil content had low contributions to seed yield.

Identification and evaluation of high nitrogen nutrition efficiency in rapeseed(Brassica napus L.)germplasm

To establish identification and evaluation methods of N(nitrogen)absorption and utilization of rapeseed(Brassica napus L.),difference of N nutrition efficiency(NNE)among rapeseed germplasms and relationship between NNE and plant traits under various N application rates were analyzed in this research.Pot cultivating experiments were conducted to investigate NNE with 3 N application rates in soil(0.05,0.2 and 0.3 g/kg).A total of 12 rapeseed germplasms were planted,nitrogen absorption efficiency(NAE)and nitrogen utilization efficiency(NUE)in seedling stage,bolting stage,initial flowering stage,final flowering stage,and maturity stage were obtained.Results showed that bolting stage was the best period for NAE identification and evaluation.Low N application rate in soil(0.05 g/kg)was the best for NAE,and the indirect indexes were basal stem diameter,plant root dry weight and above ground plant dry weight.Maturity stage was the best period for NUE identification and evaluation.High N application rate in soil(0.3 g/kg)was the best for NUE,and indirect indexes were above ground plant dry weight and basal stem diameter.N application rates of 0.05 g/kg in soil was the best for nitrogen harvest index at maturity stage,and indirect indexes was number of pods per plant.Plant traits of rapeseed germplasms affected NNE.Higher basal stem diameter,plant root dry weight and above ground plant dry weight at bolting stage under low N application rate were important characteristics of N absorption in rapeseed.Higher above ground plant dry weight and basal stem diameter at maturity stage under high N application rate were important characteristics of N utilization.Higher number of pods per plant at maturity stage under lowe N application rate was an important characteristic of N harvest index.These results provided a reliable index for N management and provided theoretical basis for guiding rapeseed breeding.

Dissecting the genetic architecture of glucosinolate compounds for quality improvement in flowering stalk tissues of Brassica napus

Glucosinolates(GSLs) and their hydrolytic products contribute to the quality traits of rapeseed flowering stalk tissues, such as taste, flavor and anticarcinogenic properties(Glucoraphanin). However, little is known about the genetic mechanisms of GSL accumulation in rapeseed flowering stalks. In this study, the variation and genetic architecture of GSL metabolites in flowering stalk tissues were investigated for the first time among a panel of 107 accessions. All GSL compounds exhibited continuous and wide variations in the present population. Progoitrin,glucobrassicanapin and gluconapin were the most abundant GSL compounds. Five quantitative trait loci(QTL) significantly associated with three GSL compounds were identified by genome-wide association study. GRA_C04 was under selected during modern breeding, in which the ratio of lower GSL haplotype(HAP2) in the accessions bred before 1990(52.56%) was significantly lower than that after 1990(78.95%). Four candidate genes, BnaA01. SOT16, BnaA06. SOT17, Bna A06. MYB51a, and Bna A06. MYB51b, were identified in the GTL_A01 and 4OH_A06 regions.These findings provide new insights into GSL biosynthesis in flowering stalk tissues and facilitate quality improvement in rapeseed flowering stalks.

Foliar K application delays leaf senescence of winter rapeseed(Brassica napus L.) under waterlogging

To better understand waterlogging effect on leaf senescence in winter rapseed (Brassica napus L.) during flowering stage, experiments were designed to explore foliar K application influences on adverse effects of waterlogging stress. Winter rapeseed was sprayed with K after waterlogging at initial flowering stage. Results indicated that waterlogging significantly decreased leaf net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr). It also declined maximum quantum yield of PS II (Fv/Fm), quantum yield of electron transport (ΦPS II) and photochemical quenching (qP), but increased leaf non-photochemical quenching (NPQ) and minimal fluorescence (Fo). Interestingly, exogenous application of K significantly alleviated waterlogging-induced photosynthesis inhibition. Foliar K application increased RuBisCO activation, chlorophyll and soluble protein contents, while significantly decreased MDA content under waterlogging stress. Moreover, K supplementation improved accumulation of K+, Ca2+, Mg2+, N, Zn2+, Mn2+, Fe2+ in leaves. In general, foliar K application is effective inalleviating deleterious effects of waterlogging stress and delays leaf senescence of winter rapeseed.