茶褐素（TBs）是普洱茶、青砖茶等黑茶的特征性功能与品质成分。茶褐素（TBs）是在黑茶的渥堆发酵加工过程中，茶多酚发生酶促和非酶促氧化聚合反应产生的一类多分子量分布、水溶性的褐色聚合物。一直以来，茶褐素的制备是以黑茶为原料进行提取纯化，但制得的茶褐素含有结合态的多糖、咖啡碱等异质成分，难以除去。分离纯化工艺繁琐，有机溶剂使用多，这使其一直难于产业化。本研究分别以表没食子儿茶素（EGC）、表没食子儿茶素没食子酸酯（EGCG）、表儿茶素没食子酸酯（ECG）、EGC/EGCG（质量比1:1）、EGCG/ECG（质量比1:1）、EGC/ECG（质量比1:1）、EGC/ECG（质量比1:1）和EGC/EGCG/ECG（质量比1:1:1）为底物，依次经多酚氧化酶（PPO）和过氧化物酶（POD）催化制得茶褐素，命名为TBs-dE-1、TBs-dE-2、TBs-dE-3、TBs-dE-4、TBs-dE-5、TBs-dE-6和TBs-dE-7。研究了TBs-dE（1-7）的理化特性和抑菌活性与机理。感官及色差测定表明7个茶褐素样品均显示不同程度的棕褐色色度。pH3.0-9.0的水溶液中的Zeta电位表明，TBs-dE（1-7）带负电荷，电势随pH增大而增大。紫外可见扫描光谱（UV-vis）显示，TBs-dE（1-7）在208 nm和274 nm处有特征吸收峰；傅里叶红外光谱（FT-IR）表明其为多酚类化合物。TBs-dE（1-7）对大肠杆菌DH 5α（E.coli DH 5α）均具有显著的抑制作用。其中TBs-dE-3的抑菌作用最强（其最小抑菌浓度MIC为1.25 mg/mL，最小杀菌浓度MBC为10 mg/mL），其次是TBs-dE-5、TBs-dE-6。选取这三种TBs-dE进一步探究其抑菌机理。结果表明，TBs-dE通过破坏大肠杆菌的胞外膜，使内容物泄漏，同时增加细胞内活性氧含量，致使因氧化应激引起细胞代谢异常起到抑菌作用。研究结果为茶褐素的产业化制备及产品开发提供理论依据。

针对双季稻高产栽培中存在氮肥用量大的问题，研究了壮秧增密减氮栽培模式对双季稻根系形态生理特性和产量的影响。结果表明，壮秧增密减氮栽培模式对双季稻单株根系形态特征的影响不显著，但对群体根系形态特征的影响显著，显著提高了群体根系鲜重、根体积、根数、根长和根干重。壮秧增密减氮栽培模式对单株根系总吸收面积和根系活性吸收面积的影响也不显著，但在分蘖期、抽穗期和成熟期显著提高了水稻群体根系总吸收面积和根系活性吸收面积。而且，壮秧增密减氮栽培模式显著增加了抽穗期水稻根系伤流强度以及伤流液中可溶性糖含量和游离氨基酸含量。与传统栽培模式（CK）相比，壮秧增密减氮栽培模式下的早稻和晚稻抽穗期根系伤流强度分别比对照高4.37%和8.90%，伤流液中可溶性糖含量分别比对照高12.85%和10.41%，游离氨基酸含量分别比对照高43.25%和37.50%。此外，由于有效穗数和结实率的提高，壮秧增密减氮栽培模式下的双季稻实际产量有所提高，2016年和2017年双季早稻实际产量分别比对照提高9.37%和5.98%，2016年和2017年双季晚稻实际产量分别比对照提高0.20%和1.41%。相关分析表明，不同生育期的大部分根系特征指标与实际产量呈显著（P<0.05）或极显著（P<0.01）正相关。

Cold stress is a major problem in rice production.  To rapidly identify genes for cold tolerance in Dongxiang wild rice (DWR, Oryza rufipogon Griff.), sequencing-based bulked segregant analysis of QTL-seq method was used to resequence the extremely resistant (R) and susceptible (S) bulks of a backcross inbred lines (BILs) population (derived from Oryza sativa×O. rufipogon) and their parents.  Single nucleotide polymorphisms (SNP)-index graphs and corresponding Δ(SNP-index) graphs (at 99 and 95% confidence levels) for R- and S-bulks detected a total of 2 609 candidate SNPs, including 58 candidate cold-tolerance genes.  Quantitative real-time PCR analysis revealed that 5 out of the 58 candidate genes had significant differences in expression between O. sativa and O. rufipogon.  Structural variation and functional annotations of the 5 candidate genes were also analyzed, and allowed us to identify 2 insertion-deletion (InDel) markers (12-7 and 12-16) that were linked with candidate genes on chromosome 12 in DWR.  These results are helpful for cloning and using cold tolerance genes from common wild rice in cultivated rice.

    Cold stress is one of the major restraints for rice production. Cold tolerance is controlled by complex genetic factor. In this study, a backcross inbred lines (BILs) population derived from an inter-specific cross (Oryza sativa L.×O. rufipogon Griff.) was used for genetic linkage map construction and quantitative trait locus (QTL) mapping. A linkage map consisting of 153 markers was constructed, spanning 1 596.8 cM with an average distance of 11.32 cM between the adjacent markers. Phenotypic evaluation of the parents and BILs under (6±1)°C cold stress revealed that the ability of cold tolerance in BILs at early seedling obeyed a skewed normal and continuous distribution. Fifteen QTLs on chromosomes 6, 7, 8, 11, and 12 were identified using survival percent (SP) and non death percent (NDP) as indicators of cold tolerance, which could explain 5.99 to 40.07% of the phenotypic variance, of which the LOD values ranged from 3.04 to 11.32. Four QTLs on chromosomes 3, 5 and 7 were detected using leaf conductivity (LC) and root conductivity (RC) as indicators of cold tolerance, ranging from 19.54 to 33.53% for the phenotypic variance explained and 2.54 to 6.12 for the LOD values. These results suggested that there might be multi major QTLs in O. rufipogon and some useful genes for cold tolerance have been transferred into cultivated rice, which would be helpful for cloning and utilizing the cold tolerance-responsive genes from wild rice.

In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon (C) and nitrogen (N). The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay (classified as Fe-Accumuli-Stagnic Anthrosols) with continuous early and late rice. In 2009, soil samples were collected (0-15 cm depth) from the field treatment plots and separated into water-stable aggregates of different sizes (i.e., >5, 2-5, 1-2, 0.5-1, 0.25-0.5 and <0.25 mm) by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.

Increasing K+ adsorption can be an effective alternative in building an available K pool in soils to optimize crop recovery and minimize losses into the environment. We hypothesized that long-term fertilization might change K+ adsorption because of changes in the chemical and mineralogical properties of a rice (Oryza sativa L.). The aims of this study were (i) to determine clay minerals in paddy soil clay size fractions using X-ray diffraction methods and a numerical diagramdecomposition method; (ii) to measure K+ adsorption isotherms before and after H2O2 oxidation of organic matter, and (iii) to investigate whether K+ adsorption is correlated with changes in soil chemical and mineral properties. The 30-yr longterm fertilization treatments caused little change in soil organic C (SOC) but a large variation in soil mineral composition. The whole-clay fraction (<5 μm) corresponded more to the fertilization treatment than the fine-clay fraction (<1 μm) in terms of percentage of illite peak area. The total percentage of vermiculite-chlorite peak area was significantly negatively correlated with the total percentage of illite peak area in the <5 μm soil particles (R=-0.946, P<0.0006). Different fertilization treatments gave significantly different results in K+ adsorption. The SOC oxidation test showed positive effects of SOC on K+ adsorption at lower K+ concentration ( 120 mg L-1) and negative effects at higher K+ concentration (240 mg L-1). The K+ adsorption by soil clay minerals after SOC oxidization accounted for 60-158% of that by unoxidized soils, suggesting a more important role of soil minerals than SOC on K+ adsorption. The K+ adsorption potential was significantly correlated to the amount of poorly crystallized illite present (R=0.879, P=0.012). The availability of adsorbed K+ for plant growth needs further study.

The objectives of the present study were to estimate genetic diversity and genetic changes of introgression lines (ILs) which derived from cultivated rice (Oryza sativa L. cv. Xieqingzao B, XB) mating with common wild rice (O. rufipogon Griff., CWR). The genetic data of 239 ILs were based on a total of 131 polymorphic microsatellite (SSR) markers distributed across the 12 chromosomes of rice. On average, these ILs possessed 77.1 and 14.31% homozygous bands from XB and CWR, respectively. Most of the ILs were clustered together with XB individual, which was revealed by principal coordinate analysis (PCA) and the program STRUCTURE analysis. The result from PCA demonstrated that some intermediate genotypes between XB and CWR were also found. Moreover, there were some genomic sequence changes including parental bands elimination and novel bands emergence in the ILs. The average Nei’s gene diversity (He) was 0.296, which was higher than that of cultivated rice. It suggested that interspecific hybridization and gene introgression could broaden the base of genetic variation and lay an important foundation for rice genetic improvement. These different genotypic ILs would provide a better experimental system for understanding the evolution of rice species and the mechanism of alien gene introgression.

Soil physical properties are important indicators of the potential for agricultural production. Our objective was to evaluate the effects of long-term inputs of green manures on physical properties of a reddish paddy soil (Fe-Typic Hapli-Stagnic Anthrosols) under a double cropping system. The common cropping pattern before the study was early-late rice-fallow (winter). The field treatments included rice-rice-fallow (R-R-WF), rice-rice-rape (R-R-RP), rice-rice-Chinese milk vetch (RR- MV), and rice-rice-ryegrass (R-R-RG). The rape, Chinese milk vetch and ryegrass were all incorporated as green manures 15 d before early rice transplanting during the following year. The soil bulk density in all green manure treatments was significantly reduced compared with the winter fallow treatment. Soil porosity with green manure applications was significantly higher than that under the winter fallow. The green manure treatments had higher 0.25-5 mm water stable aggregates and aggregates stabilities in the plow layer (0-15 cm depth) compared with the fallow treatment. The mean weight diameter (MWD) and normalized mean weight diameter (NMWD) of aggregates in the green manure treatment were larger than that with the winter fallow. Soil given green manure retained both a higher water holding capacity in the plow layer soil, and a larger volume of moisture at all matric potentials (-10, -33 and -100 kPa). We conclude that the management of double-rice fields in southern central China should be encouraged to use green manures along with chemical fertilizers to increase SOC content, improve soil physical properties and soil fertility.

Drought stress is one of the major constraints to rice (Oryza sativa L.) production and yield stability especially in rainfed ecosystems and is getting worse as the climate changes worldwide. Dongxiang wild rice (DXWR) Oryza rufipogon Griff., contains drought resistant gene. Improving drought resistance of cultivars is crucial to increase and stabilize rice grain yield via transferring resistant gene from species related to rice. In this paper, four upland rice, sixty backcross inbred lines (BILs) derived from BC1F5 of R974//DXWR/R974, and their parents were employed to evaluate drought-resistance at seedling stage in the greenhouse. Nine traits were recorded for assessment of drought resistance, including maximum root length (MRL), number of roots (NR), shoot length (SL), dry root weight (DRW), fresh root weight (FRW), root relative water content (RRWC), leaf relative water content (LRWC), level for rolling leaf (LRL), and seedling survivability under repeat drought (SSRD). Using more than 88% of accumulative contribution resulted from the principal component analysis (PCA), the nine traits were classified into five independent principal components and the line 1949 showed the highest resistance. Analysis on the stepwise regression equation and correlation demonstrated that MRL, RN, FRW, and RRWC significantly influenced the drought resistance, thus could be used as comprehensive index for drought resistance at the seedling stage. Using the major gene plus polygene mixed inheritance model of quantitative traits, the inheritance of drought-resistance of BIL population at seedling stage was mostly controlled by two independent genes plus polygene. As a result, the DXWR could be precious resources for genetic improvement of drought resistance in cultivated rice.