低升糖指数水稻研究进展

大米是典型的淀粉丰富的食物,是全世界大多数人口尤其是亚洲人口每日主要的卡路里来源。目前水稻品种大多数属高升糖指数(全称为血糖生成指数,glycemic index, GI)水稻,会诱发由于高热量摄入而致血糖失调的健康问题。已有大量研究者在探索降低大米血糖指数的方法。本文重点对稻米升糖指数的影响因素、筛选方法、遗传基础以及遗传改良等的相关研究进行总结,并对未来的研究方向提出了一些建议。     

智利的小麦科研与生产

智利是南美洲最重要的小麦生产国家之一。本文主要介绍了河南省超级小麦育种与栽培技术考察团在智利访问考察期间所了解到的有关智利小麦生产、品种改良、高产栽培研究和小麦加工贸易等情况,以供国内小麦生产和科研工作者参考。     

失稳状态下土坡稳定分析的改进条分法

圆弧条分法是土坡稳定性分析的常用方法之一，但该法以假定各土条稳定性相等且与整个土坡相等为基础，属于不严密的刚体极限平衡法，存在一定的不合理性。以简单土坡为研究模型，运用改进条分法，研究了土坡失稳且土条问稳定性不等时，各土条问的传力特点、滑动规律及加速度协调条件；推导出了土坡失稳情况下，计算条间力大小及各土条稳定系数的理论公式。算例验证表明，这种方法不仅能准确分析整个土坡的稳定性，而且揭示了土坡内局部土条的稳定状态，对于实际施工具有重要参考价值。     

利用优质牧草改造低丘红壤侵蚀劣地的研究

为探索改造利用浙西低丘红壤侵蚀劣地的有效措施,引进牧草品种83个,进行小区对比试验和推广性中间试验,对其适应性、产草量、草质等指标进行综合评定,优选出一级品种8个,二级品种27个。试验表明,在侵蚀劣地上种植牧草,可减少地表径流量50％～60％,减少泥沙冲刷量60％～90％;连作三年黑麦草一年箭舌豌豆,试验区与空白对照区相比,有机质、全氮、全磷、全钾分别增加了326％、236％、94％、22％。五年来已在红壤侵蚀劣地推广种植优质牧草400余hm~2,净增产值60～100万元。     

Phosphorus desorption and isotope exchange kinetics in agricultural soils

To improve phosphorus (P) fertilization and environmental assessments, a better understanding of release kinetics of solid-phase P to soil solution is needed. In this study, Fe (hydr)oxide-coated filter papers (Fh papers), isotopic exchange kinetics (IEK) and chemical extractions were used to assess the sizes of fast and slowly desorbing P pools in the soils of six long-term Swedish field experiments. The P desorption data from the Fh-paper extraction of soil (20 days of continual P removal) were fitted with the Lookman two-compartment desorption model, which estimates the pools of fast (Q₁) and slowly (Q₂) desorbing P, and their desorption rates k₁ and k₂. The amounts of isotope-exchangeable P (E) were calculated (E_1min to E_{>3 months}) and compared with Q₁ and Q₂. The strongest relationship was found between E_{1 min} and Q₁ (r² = .87, p < .01). There was also an inverse relationship between the IEK parameter n (the rate of exchange) and k₁ (r² = .52, p < .01) and k₂ (r² = .52, p < .01), suggesting that a soil with a high value of n desorbs less P per time unit. The relationships between these results show that they deliver similar information, but both methods are hard to implement in routine analysis. However, Olsen-extractable P was similar in magnitude to Q₁ (P-Olsen = 1.1 × Q₁ + 2.3, r² = .96), n and k₁ were related to P-Olsen/P-CaCl₂, while k₂ was related to P-oxalate/P-Olsen. Therefore, these extractions can be used to estimate the sizes and desorption rates of the different P pools, which could be important for assessments of plant availability and leaching.     

上海新建园林绿化土壤的质量调查研究

土壤是农业发展的物质基础,其质量是园林绿化工程的重中之重,也是园林工程成功与否的决定性因素。对2018年-2020年上海市16个区涉及的150个园林绿化项目进行调查研究,结果显示大部分土壤呈弱碱性,EC值偏低,有机质含量整体偏低,但是土壤改良技术已经逐步应用于园林绿化工程中,盐碱土或贫瘠土可通过水渗透或添加改良材料等方法进行质量控制,效果已逐渐显现。该研究为园林绿化工程的监管提供有力的支撑。     

Do cooperatives participation and technology adoption improve farmers’ welfare in China? A joint analysis accounting for selection bias

This study examines the impact of farmers' cooperatives participation and technology adoption on their economic welfare in China. A double selectivity model(DSM) is applied to correct for sample selection bias stemming from both observed and unobserved factors, and a propensity score matching(PSM) method is applied to calculate the agricultural income difference with counter factual analysis using survey data from 396 farmers in 15 provinces in China. The findings indicate that farmers who join farmer cooperatives and adopt agricultural technology can increase agricultural income by 2.77 and 2.35%, respectively, compared with those non-participants and non-adopters. Interestingly, the effect on agricultural income is found to be more significant for the low-income farmers than the high-income ones, with income increasing 5.45 and 4.51% when participating in farmer cooperatives and adopting agricultural technology, respectively. Our findings highlight the positive role of farmer cooperatives and agricultural technology in promoting farmers' economic welfare. Based on the findings, government policy implications are also discussed.     

Associating SSR Markers with Soybean Resistance to Iron Deficiency Chlorosis

Abstract

Iron deficiency chlorosis (IDC) causes soybean yield loss to growers when certain varieties are planted on calcareous soils. Planting IDC‐resistant varieties is the best management practice, although they may still exhibit chlorosis under certain environmental conditions. Environmental variation for chlorosis expression impedes progress in improving IDC resistance. Breeders could use molecular marker‐assisted selection (MAS), an environment‐independent tool, to improve soybeans' resistance to IDC. Our objective was to determine the efficiency of simple sequence repeat (SSR) markers in selecting for IDC resistance in soybean. A breeding population was developed using parents differing in IDC resistance and yield potential. The population was advanced to the F₂ and F_2:4 generations. Foliar chlorosis data were recorded for parents and F_2:4 lines in replicated field tests planted on calcareous soils at two Iowa locations in 2000 and 2001. Chlorosis scores between parents and F_2:4 lines varied according to location and year. Genotypic data were obtained on individual F₂ plants, and association between chlorosis scores and allele segregation was tested by single‐factor analysis of variance using 2001 data. Three SSR markers were associated (P ≤ 0.1) with chlorosis scores at each location; however, the identity of the markers associated with chlorosis scores was different at each location. In addition, two SSR markers associated with IDC resistance were examined for their efficacy in improving breeding efficiency. Preliminary data presented herein demonstrate the importance of environment on expression of this soil‐stress factor and the potential of using SSR markers as an environment‐independent selection tool for breeding IDC resistance in soybean.     

高效木质纤维素分解菌群筛选及其酸碱调节能力研究

为获得能够改良土壤酸碱性的微生物群体, 以混合堆放牛粪、鸡粪的储粪池外围土样为材料, 采用限制培养技术筛选了一组木质纤维素分解菌群, 并对该菌群在不同初始pH下的适应能力和纤维材料的分解能力及其耐盐特性进行了研究。结果表明: 以不同碳源(滤纸、玉米秸秆、稻草秸秆和小麦秸秆)制作不同初始pH(5.0~11.0)的培养基, 接种木质纤维素分解菌群后培养基pH均迅速向中性变化, 第3 d集中至8.0左右, 6 d后稳定至7.8~8.6; 7 d内滤纸、玉米秸秆、稻草秸秆和小麦秸秆失重率分别超过93.15%、50.53%、44.29%和42.60%; 以滤纸为惟一碳源、NaCl浓度2.0%的培养基接种, 7 d滤纸失重率达84.82%。木质纤维素分解菌群具有较强的适应及调节pH能力, 且能够高效分解木质纤维材料, 并具有一定的耐盐特性, 可见该菌群在酸碱土壤酸碱性改良领域具有一定开发潜力。     

Differentiation of neurons from mouse induced pluripotent stem cells in vitro

AIM: To study the induction method of mouse induced pluripotent stem cells (iPSCs) that differentiate into neurons in vitro. METHODS: Mouse iPSCs were cultured in non-adherent culture dishes for 2 d to form embryoid bodies (EBs). The EBs were cultured for consecutive 2 d in the presence of retinoic acid (RA), and then were plated in the serum-free medium for adherent culture. Seven days later, Pasteur pipette was used to detach the differentiated cells around adherent EBs into “fragment” cell colonies with the help of dissecting microscopes, and these “fragments” were transferred to culture dishes with neural stem cell medium. Another 7 days later, the cells were plated onto the culture dishes using differentiation medium containing fetal bovine serum (FBS) and RA. The morphological changes of the cells were observed under inverted microscope. The iPSCs markers Oct4, Sox2 and SSEA1, the neural stem cell (NSC) marker nestin, the neuronal marker microtubule-associated protein 2 (MAP-2), the astrocyte marker glial fibrillary acidic protein (GFAP) and oligodendrocyte marker myelin basic protein (MBP) were detected by immunofluorescence method. The mRNA expression of GFAP, nestin, β3-tubulin, MAP-2 and MBP was detected by RT-RCR. MAP-2 gene sequence was identified. The proportions of NSCs differentiated from iPSCs and neurons from NSCs were detected by flow cytometry. RESULTS: Mouse iPSCs strongly expressed Oct4, Sox2 and SSEA1, and formed spherical EBs by suspended culture. The EBs were induced by RA and serum-free medium in adherent culture for 2 d, and rosette structure was observed under the microscope. “Fragments” separated by Pasteur pipette from the rosette structure formed neurosphere-like colonies. After the colonies were cultured in adherent condition for 5 d to 7 d in the presence of RA and FBS, the typical neurite was observed under the microscope. The neurospheres expressed nestin and their differentiated derivatives expressed MAP-2, GFAP and MBP, respectively. RT-PCR analysis and gene sequencing showed that the neurons were induced successfully. The results of flow cytometry demonstrated that 63.93%±1.47% of iPSCs differentiated into NSCs and 21.4%±1.70% of NSCs differentiated into neurons. CONCLUSION: Mouse iPSCs proliferate stably and differentiate into neurons in vitro, which provide a reliable source for the treatment of spinal cord injury.