壮苗的形成对提高作物产量具有重要意义。为探索玉米自交系壮苗的形成基础，本试验研究了在玉米自交系幼苗形成过程中，影响种子贮藏物质转化和分配的因素。将3种玉米自交系作为试验材料，探究种子在幼苗建成过程中，种子大小、种子活力、光照时长、温度、沙床含水量和沙床盐浓度等因素对种子贮藏物质转化和分配的影响。研究结果表明，小粒种子的物质利用率比大粒种子高3.69-17.71% 。适当延长光照时间有利于形成壮苗。低温、干旱和盐胁迫等因素在一定程度上降低了种子贮藏物质利用率，提高了根苗比。以上研究结果可用于指导玉米自交系材料苗期的田间管理，对于改良玉米种质，提高种子贮藏物质利用率，形成壮苗有着重要意义。

草甘膦靶标酶是5-烯醇式丙酮酸莽草酸-3-磷酸合酶(EPSPS)，EPSPS基因的过表达是杂草抗草甘膦的分子机制之一。比较抗型和敏感型牛筋草中EPSPS基因调控序列，发现抗型牛筋草EPSPS基因5’端非翻译区5’-UTR Py-rich stretch元件发生突变，且该突变与提高抗草甘膦牛筋草EPSPS基因转录水平相关。然而，与该元件及整个EPSPS基因启动子序列结合的关键转录因子尚未可知。为进一步探究抗草甘膦牛筋草中EPSPS基因的转录调控机制，本研究利用RNA-seq技术分析了抗草甘膦牛筋草EPSPS过表达相关的基因调控网络，筛选出相关转录因子；通过酵母单杂交技术体外验证相关转录因子与5’-UTR Py-rich stretch元件的结合情况。转录本差异表达分析显示，与草甘膦敏感型(GS)牛筋草相比，抗草甘膦牛筋草在草甘膦处理后有2752个unigenes的表达增加，4025个unigenes的表达减少。其中，鉴定出1373个unigenes与EPSPS基因共表达。GO和KEGG通路分析表明，上调的unigenes主要富集于叶绿体，并与莽草酸生物合成通路、叶绿素II和过氧化物酶体代谢过程相关。值得注意的是，催化莽草酸转化为莽草酸3-磷酸(S3P, EPSPS的底物)的莽草酸激酶的表达也上调。筛选到8个转录因子可能参与EPSPS表达，其中预测三个转录因子(ARF2, ARF8和BPC6)能与5 ' utr Py-rich元件结合。酵母单杂交实验表明ARF8和BPC6能与野生型5’-UTR Py-rich stretch元件结合，但不再能与其突变体结合。本研究数据表明，与草甘膦敏感型牛筋草相比，抗草甘膦牛筋草中EPSPS的表达转录调控机制发生了显著的变化。首次筛选分析出与EPSPS基因表达调控相关的转录因子，可为进一步研究基于EPSPS过表达的牛筋草抗草甘膦机理提供了新的参考。

油菜（甘蓝型，Brassica napus L）是世界上最重要的油料作物。油菜在种子成熟后期快速地积累油脂。然而，在种子成熟后期，人们对油菜种子的油脂积累和种皮颜色变化机制却知之甚少。本研究中，我们分析了油菜种子发育后期即开花后25天至70天，种皮、糊粉层和子叶的超微结构特征。研究结果表明，子叶中的叶绿体退化成非光合作用的质体从而导致子叶由绿色转变为黄色。糊粉层中的叶绿体退化成没有包膜的质体残余物，而子叶细胞中的叶绿体则退化成具有完整内膜和外膜的前质体。从开花后40天到70天，在糊粉层和子叶细胞中，叶绿体退化成没有类囊体的质体，油体与质体或蛋白体直接接触互作，细胞内的内质网较少；同时，油菜种子中的叶绿素含量降低并伴随着油脂含量升高。这些结果说明，在油菜种子发育后期，油脂的快速合成不依赖叶绿体光合作用产生的NADPH(主要的还原力)，可能是利用氧化磷酸戊糖途径等其他来源的还原力。质体、细胞质或油体中的甘油三酯合成相关的酶可能参与了子叶和糊粉层细胞中甘油三酯的合成。

为筛选大豆香味种质，建立大豆叶片中香味特征化合物2-乙酰基-1-吡咯啉（2-acetyl-l-Pyrroline，2AP）的鉴定方法。本研究通过单因素及三因素四水平（L9 (34)的正交试验，以峰形、总峰面积及检测样品时间为考察指标，建立了利用气质联用仪（GC-MS）快速检测香味的方法，明确了仪器运行最佳参数包括：柱温70℃，进样口温度180℃，以及样品最优萃取时间条件（酒精含量1ml、NaCl含量0.1g，超声时间10min，萃取时间为1h）。该检测方法重复性好、简单快速、样本试剂消耗少，可精准快速测定2AP含量。利用该方法对不同地理来源的101个大豆基因型进行了分析筛选。结果表明， 2-AP平均含量为0.29ppm，变幅为0.094ppm到1.816ppm，遗传多样性指数为0.54。可被划分为3个等级，其中，1级香型大豆有7份，包括中龙608、黑农88、哈13-2958、红面豆、黑农82、黄毛豆、吉育21。本研究建立的方法及筛选的优异种质为大豆香味育种和基因发掘提供了技术和材料支撑。

Received  21 December, 2017    Accepted  14 March, 2018

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Sucrose synthases (SUS) are a family of enzymes that play pivotal roles in carbon partitioning, sink strength and plant development.  A total of 11 SUS genes have been identified in the genome of Malus domestica (MdSUSs), and phylogenetic analysis revealed that the MdSUS genes were divided into three groups, named as SUS I, SUS II and SUS III, respectively.  The SUS I and SUS III groups included four homologs each, whereas the SUS II group contained three homologs.  SUS genes in the same group showed similar structural characteristics, such as exon number, size and length distribution.  After assessing four different tissues, MdSUS1s and MdSUS2.1 showed the highest expression in fruit, whereas MdSUS2.2/2.3 and MdSUS3s exhibit the highest expression in shoot tips.  Most MdSUSs showed decreased expression during fruit development, similar to SUS enzyme activity, but both MdSUS2.1 and MdSUS1.4 displayed opposite expression profiles.  These results suggest that different MdSUS genes might play distinct roles in the sink-source sugar cycle and sugar utilization in apple sink tissues.

To explore the relation of maize grain texture and phenotypic traits with grain thin-layer drying rate, we observed the ultra- structure of maize grain, and tested three traits about the maize grain texture and four phenotypic traits. The vitreous part percentage was different (P<0.05) among different maize inbred lines. There was a significant relationship between the drying rate with grain texture and phenotypic traits. Main factors that influenced the drying rate were different during different drying stages. New results observed that empirical constants (k and N) in drying equation were different for seed of the 30 inbred lines of maize. The k of simplified diffusion equation and N of page equation were significantly influenced by both grain texture and phenotypic traits. These results could be used as guideline parameters for drying maize seeds having different grain characteristics during different drying stages.

Glyphosate has been used worldwide for nearly 40 years, and 30 types of resistant weeds have been reported. Glyphosate is mass-produced and widely used in China, but few studies and reports on glyphosate-resistant weeds and resistance mechanisms exist. Previous studies found a goosegrass species with high glyphosate resistance from orchards in South China and its glyphosate resistant mechanism was described in this study. The cDNA of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19), the target enzyme of glyphosate, was cloned from the glyphosate-resistant and -susceptible goosegrass, respectively, and referred as EPSPS-R and EPSPS-S. The Pro106 residue was known to be involved in the glyphosate resistance in most goosegrass populations. However, sequence analysis did not find the mutation at the Pro106 residue in the R biotype EPSPS amino acid sequence. The residue 133 and 382 was mutated in the R biotype EPSPS amino acid sequence instead, but it did not affect the EPSPS-S and EPSPS-R genes sensitivities to glyphosate. RT-PCR and Western blot analyses suggested that EPSPS mRNA and protein are mainly present in the shoot tissues both in the R and S goosegrass biotypes. The EPSPS-R rapidly responds to the glyphosate in R-biotype goosegrass and the induced expression was detected at 12 h post glyphosate treatment. The mRNA and protein expression of EPSPS-R increased constantly as the increasing concentration of glyphosate. However, the expression of the EPSPS-S was not induced significantly by glyphosate in the S goosegrass biotype. Quantification of real-time PCR results showed that the copy number of the EPSPS in R-biotype goosegrass was 4.7 times higher than that in the S goosegrass biotype. All the results implied that EPSPS gene amplification might mainly caused the glyphosate resistance of a goosegrass population collected from orchards in South China.

The harpin protein Hpa1 produced by the rice bacterial blight pathogen promotes plant growth and induces plant resistance to pathogens and insect pests. The region of 10-42 residues (Hpa110-42) in the Hpa1 sequence is critical as the isolated Hpa110-42 fragment is 1.3-7.5-fold more effective than the full length in inducing plant growth and resistance. Here we report that transgenic expression of Hpa110-42 in wheat induces resistance to English grain aphid, a dominant species of wheat aphids. Hpa110-42-induced resistance is effective to inhibit the aphid behavior in plant preference at the initial colonization stage and repress aphid performances in the reproduction, nymph growth, and instar development on transgenic plants. The resistance characters are correlated with enhanced expression of defense-regulatory genes (EIN2, PP2-A, and GSL10) and consistent with induced expression of defense response genes (Hel, PDF1.2, PR-1b, and PR-2b). As a result, aphid infestations are alleviated in transgenic plants. The level of Hpa110-42-induced resistance in regard to repression of aphid infestations is equivalent to the effect of chemical control provided by an insecticide. These results suggested that the defensive role of Hpa110-42 can be integrated into breeding germplasm of the agriculturally significant crop with a great potential of the agricultural application.

China is one of the most important rapeseed producing countries in the world. Effective mechanical harvesting time for decreasing harvesting loss of winter oilseed rape has been becoming a critical factor. An elite cultivar Zhongshuang 11 (Brassica napus L.) was employed in two rounds of field experiments from 2009 to 2011. Seeds were sown with machine, three combine harvesting times namely combine harvesting A, B, and C (CHA, CHB, and CHC) were designed and manual harvesting (MH) as control was performed at maturity. The harvesting treatments were determined according to color of pod and seed in the field. Seed yield loss and quality in different treatments were evaluated. Results showed that both seed yields and harvesting losses in 2009-2010 were higher than that in 2010-2011, whereas seed oil contents in 2010-2011 were higher than that in 2009-2010. The highest yield appeared in CHB, which was significantly higher than that in MH. Furthermore, harvesting loss in CHB were 50% that in MH. Seed oil content and chlorophyll exhibited no obvious difference between CHB and MH. Economic profit analysis demonstrated that mechanical sowing/combine harvesting (MS/CH) showed an input/output ratio of 1:1.6, and it was 1:1.2 in mechanical sowing/manual harvesting (MS/MH). Labor-cost accounted for more than 70% of the total cost in MS/MH, which led to low profitability to a great extent. Our results suggested that CHB was the optimum harvesting time for winter oilseed rape along the Yangtze River.