Effects of nitrogen and water stress on the rehydration,endogenous hormonal regulation and yield of maize

Water scarcity is known to be a strong limiting factor affecting maize grown and yield in cold semi-arid regions. Numerous studies have shown that rehydration improves maize growth. Our study aimed to explore the effects of rehydration treatments on maize growth and yield under water and nitrogen stress during different growth stages. We selected the drought-tolerant maize variety Nendan 19 (ND19) and subjected it to water stress during the V6 (sixth-leaf), R2 (filling) and R6 (maturity) growth stages and a rehydration treatment after each stress stage. Our results indicated that N1 (N100 kg N ha⁻¹) and N3 (N300 kg N ha⁻¹) treatments significantly increased the leaf moisture status relative to water content (RWC), bound water content (BWC), free water content (FWC) and water potential (WP)) at different growth stages. Similar trends were observed in the accumulation of plant leaf and root hormones (zeatin+zeatin riboside, indole-3-acetic acid, abscisic acid and gibberellic acid), photosynthetic pigments and chlorophyll fluorescence. However, under the same water stress conditions, they decreased as the N rate increased and reached a minimum value in the S3 (water stress for N3) treatments. In addition, with growth stage advancement and extension of the rehydration time, both showed a gradual upward trend. The results showed that to save water resources in the cold semi-arid region, rehydration treatments (R2S1 and R2S3) significantly increased the photosynthetic pigments and chlorophyll fluorescence parameters, leaf moisture status, biomass, 100-grain weight, hormone content, ear characteristics and grain yield of maize.     

Study on the relationship between genetic variation of DNA methylation and heterosis in soybean leaves

In order to well understand the molecular basis of heterosis in soybean, the methylation-sensitive amplification polymorphism (MSAP) method based on capillary electrophoresis was used to estimate levels and patterns of cytosine methylation in 15-day post-emergence leaves of four parental lines [Jilin 47 (no. 19), EXP (no. 12), Jilin 38 (no. 3) and Yi 3 (no. 6)] and 12 hybrids [Jilin 38 × Yi 3(3 × ?6), Jilin 38 × ?EXP(3 × ?12), Jilin 38 × ?Jilin 47(3 × ?19), Yi 3 × ?Jilin 38(6 × ?3), Yi 3 × ?EXP(6 × ?12), Yi 3 × ?Jilin 47(6 × ?19), EXP × Jilin 38(12 ×?3), EXP × Yi 3(12 × ?6), EXP × ?Jilin 47(12 × ?19), Jilin 47 × ?Jilin 38(19 × ?3), Jilin 47 × Yi 3(19 × 6), Jilin 47 × EXP(19 × 12)]. In addition, 12 traits of the hybrids and their parents were also analyzed to understand the relationship between DNA methylation variation and heterosis. MSAP results showed that the total relative methylation level of all hybrids was lower than the corresponding middle parent value, indicating that the methylation degree was decreasing. And may express a variety of genes related to the phenotypic variation of hybridization. Moreover, the hemi-methylation levels of Jilin 38 × Jilin 47 and Yi 3 × Jilin 47 hybrids and full-methylation levels of EXP × Yi 3 and EXP × Jilin 47 hybrids was significant higher than the corresponding mid-parent values. In addition, the heredity of methylation from parents in hybrids is more than the variations, in which there were four types appeared great higher: A1, B4, B8, and D2. Furthermore, the results of relationship between genetic variation in DNA methylation and heterosis showed that the hypo-methylation had a promoting effect to increase node number, and the hype-methylation of hybrids was helpful to add to stem thick. Our results may provide new insights into well understanding the molecular mechanisms of heterosis at the epigenetic level in soybean.     

生物炭与肥料配施对土壤养分及玉米产量的影响

采用田间试验的方法,设无生物炭无肥料(CK)、常规施肥(F1)、80%常规施肥(F2)、80%常规施肥+20%生物炭(F2B)、70%常规施肥(F3)以及70%常规施肥+30%生物炭(F3B)6个处理,研究生物炭和肥料配施对土壤有机质、全氮、有效磷、速效钾及玉米不同生育期干物质积累和产量的影响。结果表明,生物炭与肥料配施处理(F2B、F3B)较单施肥处理(F2、F3)在不同程度上提高土壤有机质、土壤全氮、有效磷、速效钾含量、玉米各生育期干物质量及产量。F2B处理的玉米产量略高于F1处理,二者差异不显著。与常规施肥相比,生物炭与化肥合理配施改善土壤养分状况。试验区最佳肥料-生物炭施用量效配比为80%常规肥+20%生物炭。     

水条播对寒地水稻农艺性状和产量构成因素的影响

随着劳动力的短缺,直播水稻具有省工省力的优点逐渐受到重视,因此筛选适宜水条播（直播）的水稻品种是极其重要的。为此,以29份寒地水稻为材料,采用随机区组试验设计,研究水条播对寒地水稻农艺性状、产量构成因素和产量的影响。结果表明,水条播对寒地水稻单位面积穗数的影响为偏正向,对株高、穗长、穗重、一次枝梗数、二次枝梗数、穗粒数、成粒率、千粒重、生物产量、经济系数和理论产量的影响都是偏负向的。水条播提高了穗重、一次枝梗数、二次枝梗数、单位面积穗数、穗粒数、成粒率、千粒重、生物产量、经济系数和理论产量的变异程度,而千粒重的变异系数较小。穗重、成粒率和生物产量对水条播反应较敏感的材料,一般其理论产量对水条播的反应也较敏感。     

收获后贮藏时间对鲜食玉米品质的影响

以12个糯玉米品种和6个甜玉米品种为试验材料，研究采收后室温下（28℃）放置0、8、16、24、32 h后对子粒中糖含量、淀粉含量、蛋白含量蔗糖代谢酶活性等的影响，探讨鲜食玉米采摘后贮藏时间对鲜食品质的影响。结果表明，鲜食玉米随着采收后时间的延长，子粒可溶性糖含量、蔗糖含量、果糖含量、还原糖含量、淀粉含量、可溶性蛋白含量以及蔗糖代谢酶活性均呈下降趋势，常温下糯玉米品质变化大于甜玉米。因此，为保证鲜食玉米的子粒品质，生产上糯玉米采收后8 h内进行冷冻贮藏。甜玉米中，先正达OVERLAND于采收后16 h内进行冷冻贮藏，京科甜183、和甜一号、和甜糯一号、先正达米哥、郑甜66于采收后8 h内进行冷冻贮藏。     

高粱硬脂酰-ACP脱氢酶基因（SbSAD）家族鉴定及不同发育阶段表达分析

硬脂酰-ACP脱氢酶是形成不饱和脂肪酸的关键酶。利用拟南芥蛋白序列作为比对序列在NCBI和Phytozome数据库进行Blastp同源比对,共鉴定11个SbSADs基因。对SbSAD基因家族进行蛋白特性、进化关系、不同发育阶段表达、基因结构、保守基序、染色体定位、基因二级和三级结构、启动子区的顺式元件及种子发育阶段表达分析,结果显示,SbSADs基因编码区为1 134~1 290bp,其编码蛋白的氨基酸数为377~449,分子量最大为48.0kDa,最小为39.8kDa,等电点为5.26~8.76;根据系统发育树,将SbSAD基因家族分为3个亚族,其中亚族I在不同组织发育阶段表达量较高;11个SbSADs基因不均等地定位在高粱1、2、3、4、6、7和10号染色体上;SbSADs蛋白二级结构均以α-螺旋和无规则卷曲为主,三级结构预测显示,除SbSAD8外,其余SbSADs的蛋白三级结构高度相似;11个SbSADs基因的启动子区与低温胁迫相关的元件数量高度富集。SbSAD5基因在种子发育5和10d均有较高的表达量。     

高粱AGO蛋白家族基因鉴定及表达分析

Argonaute (AGO)蛋白是RNA介导的沉默复合物RISC的核心成分,在小RNA、Dicer?like酶等的协同下共同激发RNA沉默反应。为阐明高粱中AGO蛋白的功能,本研究采用生物信息学的方法首次在高粱全基因组水平鉴定15个SbAGOs,分别定位于高粱的7条染色体上,根据氨基酸序列将其划分为三个亚家族。亚家族Ⅲ中SbAGO7和SbAGO3都含有3个外显子,亚家族Ⅱ中SbAGO4和SbAGO6都具有22个外显子,成员最多的亚家族Ⅰ中基因外显子数量介于19~24之间。其中,亚家族Ⅰ中SbAGO1-1和SbAGO1-3、SbAGO1-3和SbAGO1-4、SbAGO5-2和SbAGO5-4发生过基因复制事件,可能存在功能冗余现象。NCBI表达谱数据库分析发现,SbAGO1-1、SbAGO1-2、SbAGO1-3和SbAGO4在高粱不同组织器官和生长发育阶段均有较高表达,其中SbAGO1-1和SbAGO1-2、SbAGO1-3和SbAGO4表达时期和表达量基本一致,可能在调控高粱生长发育方面发挥协同作用。高温、干旱及高温与干旱复合逆境表达谱芯片数据分析发现,高温处理引起5个SbAGOs基因差异表达,干旱处理SbAGOs表达变化不明显,复合逆境引起7个SbAGOs基因差异表达;2个处理共同差异表达基因为SbAGO1-3、SbAGO1-1、SbAGO5-2和SbAGO3,表达量变化趋势相近。其中SbAGO1-1、SbAGO1-2、SbAGO1-3和SbAGO5-6下调表达,SbAGO3、SbAGO5-2、SbAGO1-4和SbAGO10上调表达。本研究结果为揭示SbAGO蛋白功能和发掘高粱的抗逆育种靶向基因资源提供了一定的理论依据。     

氮肥运筹对寒地水稻籽粒植酸、蛋白质和矿质元素的影响

为探究寒地水稻优质栽培的氮肥施用方式,以粳稻品种垦粳7号和垦粳8号为试验材料,通过2年(2017-2018年)田间试验,设置4种氮肥运筹方式:习惯施肥(T1,施氮量150 kg·hm^-2,基肥:蘖肥:穗肥=6:3:1)、氮肥后移1(T2,施氮量150 kg·hm^-2,基肥:蘖肥:穗肥=4:3:3)、基于T2的减氮施肥(T3,施氮量135 kg·hm^-2,基肥:蘖肥:穗肥=4:3:3)和氮肥后移2(T4,施氮量150 kg·hm^-2,基肥:蘖肥:穗肥=5:3:2),其中以T1为对照,研究氮肥运筹对寒地水稻籽粒植酸、总蛋白质及组分、矿质元素含量的影响及其互作效应。结果表明,氮肥、品种对水稻籽粒中植酸含量的影响均达显著或极显著水平。与T1相比,T2、T3和T4水稻籽粒中植酸含量平均分别显著降低了31.92%、48.94%和21.28%;T2、T3和T4水稻籽粒中清蛋白、球蛋白、谷蛋白以及总蛋白质含量均增加,且T2作用效果更明显,分别较T1显著提高了0.14、0.10、0.45和0.60个百分点(2017年两品种均值);T2和T3的醇溶蛋白含量略有降低,T4则略有增加,但与T1差异均不显著;T2和T3水稻籽粒中Cu、Mn、Fe、Ca、K、Zn含量均增加,且T2增加更明显,T4水稻籽粒中各矿质元素含量变化则无明显规律。通过分析氮肥运筹下水稻籽粒植酸含量与蛋白质、8种矿质元素含量的相关性可知,植酸含量与总蛋白质、清蛋白、球蛋白、谷蛋白以及Cu、Mn、Fe、Zn、Ca、Mg、K含量均呈负相关,其中与球蛋白含量和2018年Zn和Ca含量呈显著负相关。综上所述,氮肥平衡分配能降低水稻籽粒中植酸含量,增加总蛋白质和矿质元素含量,有效改善蛋白质组分,从而提高稻米营养品质。本研究结果为寒地稻米的优质栽培的氮肥运筹方式提供了理论依据。     

不同维生素浸种对玉米种子萌发的影响

以玉米杂交种郑单958为试验材料,采用不同质量浓度50、100、200 mg/L的水溶性维生素V_(B1)、V_(B2)、V_(B6)、V_(B12)、V_C、V_H、V_(PP)浸种24 h,处理后分析玉米种子萌发及胚芽和根生长中脯氨酸等可溶性调节物质情况。结果表明,供试维生素在100、200 mg/L处理下基本都呈现对种子萌发指数的促进,其中,100 mg/L维生素处理对种子萌发率促进效果显著;200 mg/L维生素处理对种子发芽势显著促进作用;50 mg/L维生素对上述3个指标的影响不同。与未处理对照相比,不同种类维生素和不同质量浓度的同一维生素对根冠比影响不同。维生素浸种均可引起玉米胚芽可溶性糖含量显著升高,外源维生素浸种处理可显著影响玉米种子萌发和胚芽及胚根的生长,且不同维生素在不同浓度下对各生长指标影响及脯氨酸等可溶性调节物质变化不尽相同,对种子萌发呈显著促进作用的V_(B2)和V_(B12)在玉米种子萌发中应用前景较好。