甘薯近缘种Ipomoea cordatotriloba基因组大小测定及高通量调查测序

利用流式细胞术,以大豆Williams 82为内参,对甘薯近缘野生种Ipomoea cordatotriloba进行基因组大小测定,结合染色体压片技术进行倍性鉴定,并利用二代高通量测序技术对测定结果进行验证。结果表明:利用流式细胞术测得I. cordatotriloba基因组大小为(539.69±13.76)Mb;染色体压片结果显示其染色体数目为30条,由于其基数x=15,从而获知I. cordatotriloba为二倍体;经K-mer计算并修正后得出的C值为560.70 Mb,与流式细胞分析结果相近;同时,测序结果显示其基因组杂合率为0.40%;重复序列比率为57.93%;GC含量为38.10%。以上结果为此物种全基因组精细图谱绘制打下基础,同时为甘薯近缘野生种的利用提供参考。     

Evaluation of validity and limitations of the soybean canopy height‐to‐row spacing ratio as an onsite index to control weeds using diverse soybean accessions

A canopy height‐to‐row spacing ratio (CHRSR) of 1.0 is expected to be a simple and practical onsite index for soybean growers to determine when further weed control is no longer necessary. This is decided when relative photosynthetic photon flux density (PPFD) reaches 50% under the soybean canopy. To evaluate the validity of this index, a 2‐year field experiment was conducted to compare days after sowing (DAS) to reach a relative PPFD of 50% (defined as PPFD50) and DAS to reach a CHRSR of 1.0 (defined as CHRSR1.0) in 190 accessions with different canopy architectures from a soybean core collection. A total of 104 accessions, for which final relative PPFD reached <10% in 2014, were examined for the differences between CHRSR1.0 and PPFD50. The mean and median values of the difference in 2014 were 0.02 and 2.2, respectively. Similarly, the mean and median values in 2015 were 2.8 and 2.6, respectively. Thus, CHRSR1.0 tended to be achieved slightly later than PPFD50, so a consideration was made that there would be a negligible risk of failure if growers used CHRSR1.0 to determine the termination time for weed control in the most of accessions. Although there were some accessions with a standing type of morphological characteristics or with a smaller or narrower leaf, showing negative differences between CHRSR1.0 and PPFD50 larger than 1 week, a CHRSR of 1.0 could be used to estimate PPFD50 in most of accessions without risk of failure to control weeds.     

Efficient production of transgenic plants using the bar gene for herbicide resistance in sweetpotato

Efficient production of transgenic sweetpotato (Ipomoea batatas (L.) Lam.) plants using the bar gene for herbicide resistance was achieved through the use of embryogenic suspension cultures and Agrobacterium tumefaciens-mediated transformation. Cell aggregates from embryogenic suspension cultures of sweetpotato cv. Lizixiang were cocultivated with A. tumefaciens strain EHA 105 harboring a binary vector pCAMBIA3300 with the bar gene and uidA gene. Selection culture was conducted using 0.5 mg/l PPT. A total of 1431 plants were produced from the inoculated 870 cell aggregates via somatic embryogenesis. GUS assay and PCR analysis of the regenerated plants randomly sampled showed that 86.5% of the regenerated plants were transgenic plants. Stable integration of the bar gene into the genome of transgenic plants was confirmed by Southern blot analysis and transgene expression was demonstrated by Northern blot analysis. The copy number of integrated bar gene ranged from 1 to 3. Transgenic plants exhibited functional expression of the bar gene by in vivo assay for herbicide resistance. This study also provides a simple and efficient transformation system of sweetpotato based on the use of bar gene as a selectable marker gene, which can be combined with other agronomically important genes for the improvement of sweetpotato.     

水培蕹菜使用吡唑醚菌酯的水生生态系统风险评估

为研究水培蕹菜使用吡唑醚菌酯对水生生物的潜在影响，在水培蕹菜白锈病发病初期，喷施25%吡唑醚菌酯悬浮剂和9%吡唑醚菌酯微囊悬浮剂，测定水培蕹菜和水体中的吡唑醚菌酯残留量，并结合毒理学数据评估其对水生生态系统的暴露风险。结果表明：吡唑醚菌酯在水培蕹菜和水中降解较快。悬浮剂和微囊悬浮剂在植株中的消解半衰期分别为2.9 d和3.9 d，微囊悬浮剂较悬浮剂在植株上的持效期更长。两种剂型在水中的消散半衰期都小于2 d，微囊悬浮剂在水中的有效浓度小于悬浮剂。基于暴露浓度峰值和时间加权平均浓度进行风险评估，悬浮剂对水生脊椎动物和无脊椎动物的急性和慢性风险商值，及其对初级生产者的慢性风险商值均大于1；微囊悬浮剂对每一类水生生物的风险商值都小于悬浮剂，但其对水生生物的急性暴露风险同样不可接受（风险商值仍大于1），慢性风险商值仅在基于时间加权平均浓度计算时小于1。研究表明，吡唑醚菌酯在水培蕹菜上使用对水生生态系统的风险不容忽视，应重点关注鱼和无脊椎动物的暴露风险。建议在水生蔬菜生产中谨慎使用吡唑醚菌酯，同时修订吡唑醚菌酯在水生蔬菜上的限量标准。     

五爪金龙两种化感作用途径释放的化学成分分析及其效应研究北大核心CSCD

五爪金龙是我国华南地区具有强入侵性的外来植物,其入侵机制与化感作用间的关系备受学者关注。通过模拟自然条件下五爪金龙挥发和淋溶两种途径的作用,发现这两种途径对三叶鬼针草和生菜种子发芽率、发芽速率表现出不同程度的抑制。继而采取顶空固相微萃取及树脂洗脱法分别收集这两种途径释放的物质,并用气相色谱与质谱联用法分析各自成分。结果表明,五爪金龙叶片挥发物被检测出18种萜烯类化合物,其中石竹烯(28.17%),β-罗勒烯(16.59%),α-蒎烯(13.65%)和β-柏木烯(9.43%)相对含量较多。淋溶水主要为酚酸类,肉桂酸(39.21%),琥珀酸(15.15%),丙酸(11.12%)及月桂酸(9.38%)相对含量居于前四。在定量得出上述主要物质实际浓度后,进一步处理受试植物发现,淋溶途径释放的肉桂酸和月桂酸显著抑制两种受体植物的种子发芽率和发芽速率,丙酸和琥珀酸则对两种受体植物大部分指标无显著影响。此外,4种主要叶片挥发物对受体植物种子萌发的影响也有明显差异,β-柏木烯和石竹烯的作用明显强于α-蒎烯和β-罗勒烯。综上所述,挥发与淋溶是五爪金龙重要的化感效应作用途径,它们分别产生以萜烯及酚酸类为代表的物质,且这两类物质对受体植物种子萌发能形成抑制,但不同物质对受体植物的抑制程度显著不同。由此可见外来植物五爪金龙产生的化感物质可以通过多种途径释放并发挥作用,其中的关键物质则对其化感作用效果产生决定性影响。     

暗纹东方鲀立体种养模式和单养模式的水质变化及养殖能效比较

为解决暗纹东方鲀单一品种的池塘养殖瓶颈问题,开发和建立多物种、多营养层次的生态立体种养池塘生态系统,本文研究了暗纹东方鲀(Takifugu obscurus,12000 ind.hm_^-2)、南美白对虾(Penaeus vannamei,24 万尾.hm_^-2)和蕹菜(Ipomoea aquatica Forsk)的立体种养模式与暗纹东方鲀传统单养模式(15000 ind.hm_^-2)的水质变化及养殖能效差异。结果显示,暗纹东方鲀立体种养模式和传统单养模式池塘水体的pH、TAN、NO₂-N和NO₃-N等水质指标总体较低、数值保持在较理想范围内,这些指标中除了7月8日立体种养模式的NO₃-N显著低于传统单养模式的,其他在两模式之间无显著性差异。立体种养模式的叶绿素a明显低于传统单养模式的。两模式的总氮均值范围分别为1.38-3.96 mg.L_^-1和1.04-3.20 mg.L_^-1,养殖中后期(7月24日-10月11日),立体种养模式的总氮高于传统单养模式。立体种养模式的总磷(TP)变化随养殖时间呈现缓慢平稳上升趋势(0.26-0.42 mg.L_^-1);而传统单养模式总磷数值在养殖中期较高、前期后期较低。除了5月6日监测COD数值相对较高外,其他监测的时间点两种养殖模式的COD数值相对较稳定,均值范围分别为6.79-10.24 mg.L_^-1和6.83-9.15 mg.L_^-1,两模式间均无显著性差异。TSS数值总体较高,特别是6月13日的水源、7月24日及8月19日的传统单养模式和9月15日的立体种养模式的TSS数值超过150 mg.L_^-1。各监测时间点的TSS数值在两种养殖模式之间无显著性差异。两种模式暗纹东方鲀的养殖均有利于池塘水体的pH、TAN、NO₂-N和NO₃-N的净化,对水体中总磷(TP)和TSS的影响不明显,但会造成水体中总氮(TN)和COD的升高。立体种养模式和传统单养模式的暗纹东方鲀生长没有显著性差异,放养密度(12000-15000 ind.hm_^-2)没有造成暗纹东方鲀生长的空间胁迫。除了立体种养模式的暗纹东方鲀的单位产量(3426.0 kg.hm_^-2)显著低于传统单养模式的(4055.7 kg.hm_^-2)外,立体种养和传统单养模式的暗纹东方鲀的出池规格(293.30 g.ind_^-1和297.53 g.ind_^-1)、成活率(97.38 %和94.60%)以及饵料系数(2.83和2.91)均无显著性差异。立体种养模式下套养的南美白对虾生长性能良好: 南美对虾产量3056.6 kg.hm_^-2,规格为22.48g.ind_^-1,存活率78.17 %,饲料系数为0.68,鱼虾叠加后的饲料系数总体为1.39。相对于暗纹东方鲀传统单养模式,立体种养模式在养殖尾水排放减少11.1%的前提下,每公顷增效102675元,每亩增效6845元。