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.

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).

活性炭对甘蓝型油菜(Brassica napus L.)小孢子胚胎发生的影响

试验以大田环境下的多份甘蓝型油菜的品种或品系为材料,研究了活性炭对游离小孢子胚胎发生的影响。结果表明:活性炭对甘蓝型油菜游离小孢子培养胚状体发生有很好的促进作用,不仅提高了胚产量,而且有利于小孢子胚的正常发育,添加活性炭的固液双层培养基效果尤为显著。

Landscape of Sequence Variations in Homologous Copies of FAD2 and FAD3 in Rapeseed(Brassica napus L.)Germplasm with High/Low Linolenic Acid Trait

Genetic manipulation(either restraint or enhancement)of the biosynthesis pathway ofα-linolenic acid(ALA)in seed oil is an important goal in Brassica napus breeding.B.napus is a tetraploid plant whose genome often har-bors four and six homologous copies,respectively,of the two fatty acid desaturases FAD2 and FAD3,which con-trol the last two steps of ALA biosynthesis during seed oil accumulation.In this study,we compared their promoters,coding sequences,and expression levels in three high-ALA inbred lines 2006L,R8Q10,and YH25005,a low-ALA line A28,a low-ALA/high-oleic-acid accession SW,and the wildtype ZS11.The expression levels of most FAD2 and FAD3 homologs in the three high-ALA accessions were higher than those in ZS11 and much higher than those in A28 and SW.The three high-ALA accessions shared similar sequences with the pro-moters and CDSs of BnFAD3.C4 and BnFAD3.A3.In A28 and SW,substitution of three amino acid residues in BnFAD2.A5 and BnFAD2.C5,an absence of BnFAD2.C1 locus,and a 549 bp long deletion on the BnFAD3.A3 promoter were detected.The profile of BnFAD2 mutation in the two low-ALA accessions A28 and SW is different from that reported in previous studies.The mutations in BnFAD3 in the high-ALA accessions are reported for thefirst time.In identifying the sites of these mutations,we provide detailed information to aid the design of mole-cular markers for accelerated breeding schemes.

Identi cation of seed heat tolerance and its correlation with agronomic traits in Brassica napus L.

To better understand the effect of high temperature on seed viability, artificial aging treatments were implemented on 472 accessions of rapeseed (Brassica napus L.) by constant high temperature at 70℃for 8h. Results showed a remarkable impact of constant heat on seed germination. After heat treatment, considerable variation was found in seed germinability, some genotypes even lost the ability to germinate. The effect of accelerated aging was highly significant. Germination parameters varied among ecotypes. Seed viability varied with different origin, and was significantly and positively correlated with seed yield per plant and dry weight of aboveground parts per plant among 14 agronomic traits. Germination traits were positively correlated with oil contents.

QTL mapping for yield components of Brassica napus L. using double haploid and immortalized F_2 populations

Effective silique number per plant(ESN), seeds per silique(SS), thousand seeds weight(TSW), silique length(SL) and silique density(SD) are important seed yield potential determinant traits in rapeseed(Brassica napus L.), which are controlled by quantitative trait loci(QTL). Mapping QTL to delimited chromosomal region offers an effective method for genetic dissection of these traits. A set of 96 double haploid(DH) lines were developed by crossing 2 Brassica napus lines R1 and R2, and an immortalized F_2(IF_2) population containing 124 combinations was developed by crossing those DH lines. DH populations were planted at 2 locations for 2 years and IF_2 populations were planted in 2 locations for 1 year. Based on the established 2,217.2 cM length high density genetic map, 42 QTLs were identified, with 26 QTLs detected repeatedly in different environments or populations, including 8 for SL, 7 for TSW, 4 for ESN, 4 for SS and 3 for SD. Among these identified QTLs, 3, 4, 1, 1 and 3 QTLs were considered as major QTLs for SL, TSW, ESN, SS and SD, respectively. In addition, 2 QTLs on A9 chromosome which control multiple traits were identified. These results warrant further study of fine mapping for yield and yield components.

Brassinosteroids promote seed development and physiological maturity of oilseed rape (Brassica napus L.)

Long developmental stage and late harvest time of winter rapeseed (Brassica napus L.) have great negative effects on rice planting of rice-rapeseed farming system in China. Early maturity improvement of rapeseed is necessary. ‘Zhongshuang 11’, an elite winter rapeseed cultivar, was used in consecutive field experiments during 2010-2012. At initial flowering stage, plants were consecutively sprayed with 0.1 mg/L 2-4-Epibrassinolide(BR) for 3 d. Two hundred sampling pods from different plants were randomly collected to measure seed related indexes with a 4 d interval from 7 to 47 d after peak anthesis (DAPA).Seed color turned light brown at 31 or 35 DAPA after BR treatment, seed dry weight (DWT)was increased while seed moisture content (SMC) was decreased during seed development.DWT almost reached the maximum value when SMC was 33.20% at 31 DAPA in 2010-2011 and 35.29% at 35 DAPA in 2011-2012 growing season after BR treatment. Similarly,the maximum values of standard germination test (SGT), accelerated aging test (AAT)and cold test (CT) were observed at 31 or 35 DAPA after BR treatment respectively. The high yield and seed oil content appeared at 31 or 35 DAPA accompanied with rapid decrease in total non-structural carbohydrate (TNC) in stems and leaves. Our study indicated that BR application advanced maturity of winter rapeseed by 4 to 8 days.

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.

Molecular Markers and Agronomic Traits of a New Kind of Genic Male Sterile Material Mian 7AB-4-2 in Brassica napus L.

[ Objective] The study was to investigate the agronomic traits and breeding characteristics of genic male sterile material Mian 7AB-4- 2 in Brassica napus. [ Method] The differences in agronomic traits and polymorphisms in SSR markers, between the genic male sterile material Mian 7AB-4-2 in Brassica napus and its sisterly line Mian 7AB-4-1 were investigated by hybridization and molecular identification; and the percentage of sterile individuals of Mian 7AB-4-2 and of the hybrids with its sisterly line Mian 7AB-4-1 from test cross and back cross were also studled. [ Result] Mian 7AB-4-2 was not significantly different in agronomic traits from its sisterly line Mian 7AB-4-1 at 0.05 probability level. The per- centages of sterile individuals in the pollinated fertile Mian 7AB-4-2 plants were over 60%, and that in its sisterly line Mian 7AB-4-1 was about 25%. In test crosses with other nine sterile lines, Mian 7AB-4-1 kept the percentage of sterile individuals of sterile lines over 90%, and the percentage of sterile individuals from back cross over 80%. With regard to molecular markers, Mian 7AB-4-2 and its sisterly line Mian 7AB-4-1 were different in the band number from SSR primers a2 and E10. [ Conclusion] The results indicate that Mian 7AB-4-2 is helpful for rapeseed breeding, quickening the application of new materials in field breeding.

Increased BnaMFT-transcript level is associated with secondary dormancy in oilseed rape (Brassica napus L.)

Brassica napus cultivars have little or no primary dormancy;however,they are prone to sec on dary dorma ncy in ducti on.Secondary dormant seeds can produce volunteer plants,which can result in genetic contamination,reduced quality and biosafety issues.However,informati on regarding the molecular mecha nism un derlyi ng sec on dary dormancy is limited.The MOTHER OF FT AND TFL1(MFT)gene,which is evolutionarily conserved in the plant kingdom,acts in a complex gene network in the seed dormancy or germination processes.In this study,we identified four B.napus genes that share high homology with AtMFT,named as BnaMFT.Analyses of c/s-acting elements showed that BnaMFT promoters contain multiple seed-specific regulatory elements,and various stress-and hormone-responsive elements.Further experiments validated that BnaMFTs were specifically expressed during seed maturation and in the dry seed,with peaks at 35-42 days after pollination.BnaMFTs were not sufficient for primary dormancy;however,they were significantly enhanced by secondary dormancy induction with PEG6000 treatment.Moreover,BnaMFTtranscripts were elevated by treatment with abscisic acid(ABA),which is known to be accumulated duri ng sec on dary dorma ncy.These results collectively suggest that increased BnaMFT tra nscription levels are associated with sec on dary dorma ncy inducti on in an ABA-depe ndent mariner in B.napus.

Tissue-specific Expression of Acetolactate Synthase (ALS), Male Sterility-inducing Effect of Tribenuron-methyl and Its Effect on ALS Activity in Brassica napus L.

[Objectives]This study was conducted to provide a basis for the rapid identification of the drug spraying effect in early stage and the molecular mechanism of chemical hybridizing in Brassica napus L.[Methods]Quantitative RT-PCR analysis showed that ALS was constitutively expressed in various tissues of 096030,including flower buds,four floral organs (calyxes,petals,stamens and pistils),roots,stems and leaves.ALS was prominently expressed in leaves and was expressed weakly in the petals and stamens.The male sterility-inducing effects of tribenuron-methyl on such two Brassica napus L.varieties as Ningyou18 and 096030 were investigated.[Results]Plants were twice sprayed with 0.2 μg/ml tribenuron-methyl on leaves.The results showed that 8-10 ml of tribenuron- methyl was applied per plant for the first time at bolting stage with 1-2 mm flower buds on 15-20 cm inflorescence,and the second spray was performed with 8-10 ml of tribenuron-methyl per plant 10 d later.The results showed that the percentage of the full sterile plants reached 100%,which lasted for the whole flowering period,and the relative seed setting rate was only about 4%.Thus,this method could fullfill the requirement of hybrid seed production in field.The in-vivo enzyme activity of acetolactate synthase (ALS) was assayed using 2 mm buds collected 3 d after spray.The results showed that 0.2 μg/ml tribenuron-methyl inhibited ALS activity.The ALS activity of Ningyou 18 (CK) and Ningyou 18 (0.2 μg/ml) was 3.20 and 1.30 μmol/(mg·h),respectively,and the ALS activity of 096030 (CK) and 096030 (0.2 μg/ml) was 3.37 and 1.25 μmol/(mg·h),respectively.The relative enzyme activity of ALS in Ningyou18 and 096030 was 40.63% and 37.23%,respectively,both of which decreased significantly.[Conclusions]These results showed that the change of ALS activity may be used as an index for quickly identifying and predicting the chemical hybridizing effect of tribenuron-methyl.

A Comparative Study on the Quality Components Between Self Pollinated Seeds and Naturally Pollinated Seeds in Brassica napus L. in Sichuan Ecological Region

[ Objective] This study was to reveal the differences in crude fat and glucosinolates between self pollinated seeds and naturally pollinated seeds in Brassica napus in sichuan ecological region.. [ Method] Near-infrared spectroscopy method （NIRS） was employed to measure the quality components in self pollinated seeds and naturally pollinated seeds of 861 shares of Brassica napus from Sichuan ecological region. And correlation analysis and regression analysis were conducted based on the experimental data via SPSS （statistics package for social science）. [ Result] The contents of crude fat in the self pollinated seeds were commonly a higher than that in the naturally pollinated seeds at 0.01 significant level; while the contents of glucosinolates in the self pollinated seeds and the naturally pollinated seeds were insignificantly different. Both the correlation relationship and linear regression for the crude fat between the self pollinated seeds and naturally pollinated seeds reached the significant level. The regression equations for the contents of crude fat（y1 ） and glucosinolates（ y2 ） in the naturally pollinated seeds and of crude fat（ x1 ） and glucosinolates（ x2 ） in self pollinated seeds were respectively determined to be y1 = 16.844 ＋0.614x1 and y2 = -0.620 ＋ 1.017 x2. [ Conclusion] In Brassica napus breeding, crude fat in naturally pollinated seeds should be emphatically taken into account, meanwhile concurrently considering that in self pollinated seeds; while glucosinolates in both the self pollinated seeds and the naturally pollinated seeds must be simultaneously concerned.

Construction of Double Cross-over Expression Vector for Chloroplast Multicistron in Brassica napus L.

[Objective] This study aimed to construct Brassica napus chloroplast multi- cistron double cross-over expression vector, to lay the foundation for the genetic engi- neering research of Brassica napus chloroplast. [Method] Two primers were designed based on the known Brassica napus chloroplast DNA sequences AF267640 and Z50868 in GenBank. By using PCR method, two Brassica napus L. chloroplast DNA fragments were obtained, which were named RbcL and ACCD. The two Brassica na- pus chloroplast DNA homologous fragments were then cloned into plasmid pMD18-T to obtain recombinant plasmid pHBM715. Tandem expression cassette harboring spectinomycin-resistant gene aadA, mannanase gene man and green fluorescent pro- tein gene gfp was cloned into the plasmid pHBM715, thereby constructing Brassica napus chloroplast multicistron double cross-over expression vector pHBM716, which was transformed into Escherichia coil for expression and identification. [Result] Plate qualitative analysis was conducted for the functional identification of expression cas- sette in the constructed Brassica napus chloroplast multicistron double cross-over ex- pression vector, results showed that the three genes of the same multicistron were all expressed in E. coil [Conclusion] This study successfully constructed Brassica napus chloroplast multicistron double cross-over expression vector, which laid the foundation for the genetic engineering of Brassica napus chloroplast.

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.

甘蓝型油菜(Brassica napus L.)隐性核不育花叶两型系的选育

用隐性核不育两型系内不育株和花叶自交系杂交 ,F1全部表现为雄性可育 ,叶型为半花叶。F2 群体出现分离 ,花叶、半花叶、圆叶三种类型植株的分离比例符合 1∶2∶1,可育植株与不育植株的分离比例符合 15∶1。在F2 群体中选花叶可育株自交 ,同时与花叶不育株兄妹交 ,F3群体内所有单株均为花叶。这些可育株自交育性分离比例为 3∶1、相应兄妹交育性分离比例为

Optimization of Culture Techniques for DH Line in Brassica napus L.

[Objective] The aim of this study is to reveal the disinfectants and disinfection methods,medium components,and embryoid culture method on dissociative microspore culture.[Method] B5 as basic medium appended with different concentrations of sucrose,agar and different hormone combinations was used to optimize the culture technique for DH line in Brassica napus L.[Result] Both the 15 min disinfection of NaClO containing 5% Cl-and 10 min disinfection of 0.1% HgCl2 performed well in disinfection and subsequent embryo production;in the extraction process of dissociative microspores,B5 medium containing 2% sucrose could achieve a good embryo production effect;under dark condition microspores were firstly incubated at 32 ℃ 5-7 d,then at 25 ℃ 12-15 d,and finally transferred to 25 ℃ oscillator(60-65 r/min)for 3-7d,when the embryoid would become full ripeness;1/2MS medium appended with 1.2% agar,0.02% NAA,2.0 mg/L 6-BA,3.4 mg/L AgNO3 and 2% sucrose was helpful for embryoid differentiation and plantlet generation,presenting low degree of browning and slight vitrification.[Conclusion] The results may facilitate DH Line in rape production in large scale and high efficient transformation system.

抗倒伏甘蓝型油菜(Brassica napus L.)木质素含量及木质素合成关键基因的表达

测定了甘蓝型油菜6个抗倒伏材料和5个易倒伏材料薹期和花期植株不同部位的木质素含量,并对木质素合成关键酶基因F5H(阿魏酸-5-羟基化酶)基因、4CL(4-香豆酸辅酶A连接酶)基因、COMT(咖啡酸/5-羟基阿魏酸-O-甲基转移酶)基因进行RT-PCR扩增,以分析抗倒伏和易倒伏材料间木质素含量的差异以及上述3个与木质素合成相关的关键酶基因的表达差异。结果显示:薹期根颈和茎部木质素含量,抗倒伏材料比易倒伏材料分别高0.95个百分点和1.90个百分点;开花期根、根颈和茎部木质素含量,抗倒伏材料比易倒伏材料分别高2.53个百分点、1.97个百分点和1.58个百分点;COMT基因在薹期和开花期的根、根颈和茎部的表达量,抗倒伏与易倒伏材料间没有明显差异;F5H基因在薹期根、茎部和开花期根部的表达量,抗倒伏材料明显高于易倒伏材料;4CL基因在薹期和开花期根、根颈的表达量,抗倒伏材料明显高于易倒伏材料;但在薹期和开花期的茎部,抗倒伏材料与易倒伏材料间4CL基因表达量差异不显著。表明,抗倒伏材料薹期和开花期根、根颈和茎部合成的木质素含量较高,F5H和4CL基因可能是与油菜抗倒伏性状相关的关键基因。

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.

吡虫啉和甲基硫菌灵对油菜(Brassica napus L.)和光叶紫花苕(Vicia sativa L.)的化感作用

油菜(Brassica napus L.)和光叶紫花苕(Vicia sativa L.)为重要蜜源植物。以这2种植物种子为受体,用不同浓度(20 mg/L、40 mg/L、60 mg/L、80 mg/L、100 mg/L)的吡虫啉和(200 mg/L、400 mg/L、600 mg/L、800 mg/L、1000 mg/L)的甲基硫菌灵采取室内培养皿滤纸法胁迫处理,以探讨这2种农药对油菜和光叶紫花苕的化感作用。结果表明,吡虫啉和甲基硫菌灵明显降低了油菜种子活力,抑制幼苗生长;吡虫啉总体上提高了苕子种子活力,促进幼苗生长,而甲基硫菌灵则降低苕子种子活力,抑制幼苗生长。总之,吡虫啉和甲基硫菌灵对上述2种蜜源植物均有强烈的化感作用。

Key genes and mechanisms underlying natural variation of silique length in oilseed rape(Brassica napus L.)germplasm

Silique length influences seed yield in oilseed rape.It shows extensive variation in germplasm resources,and identifying the underlying genes and regulatory mechanisms would advance breeding for the trait.In the present study,a genome-wide association study(GWAS)using 331 core accessions planted in 10 environments revealed 13 loci associated with silique length on chromosomes A01,A04,A07,A09,and C03,explaining 6.2%–19.2%of phenotypic variance.Physiological analysis showed that silique length variation was attributable to differences in silique growth rate and/or duration before four weeks after flowering,with levels of endogenous phytohormones(auxin,ethylene,and GA24,GA12,and GA44)playing an important role.Cytological analysis showed that silique length variation was due mainly to differences in cell number followed by cell size.Transcriptomic analysis of two pools of silique walls with opposite length extremes revealed 3248 differentially expressed genes(DEGs).These DEGs were enriched in several pathways(such as cell wall,cell division,and hormone metabolism)associated with cell proliferation and expansion and silique development.Integrating GWAS,RNA-seq,and functional annotation results revealed 15 candidate genes for the major associated locus q SL.A09-3.Of these,Bna A9.ARF18 and Bna A9.CYP78 A9 were validated by haplotype analysis followed by candidate gene association.Sequence variation in the coding region of Bna A9.ARF18 and expression of Bna A9.CYP78 A9 in silique walls were strongly associated with silique length.Our results provide an explanation for the natural variation of silique length in oilseed rape germplasm and offer useful information for its improvement.