Effect of nutrients and liming on changes in pH,redox potential,and uptake of iron and manganese by wetland rice in iron-toxic soil

In a greenhouse experiment, the nutrients NPK, NPK + lime, K, and Mn were applied to an iron-toxic soil (Typic Haplastulf). Soil pH and dry matter production were increased and Eh and available Fe in the soil were decreased. Though liming the soil decreased available Fe and Mn and increased pH to the greatest extent, the highest dry matter production was obtained with NPK application. NPK + lime produced a smaller yield than NPK without lime. Though the application of K or Mn alone produced much less dry matter than NPK or NPK + lime, no symptoms of Fe toxicity were observed. We conclude that Fe toxicity can be reduced with a balanced use of fertilizers (NPK or NPK + lime) and its occurrence was mostly due to nutrient stress.     

Temporal variation in mineral nitrogen in soil as influenced by incorporation of legume or cereal residues under submergence or well drained conditions

A laboratory study was conducted at the Indian Agricultural Research Institute, New Delhi on a sandy clay loam soil of pH 7.9 and organic C content of 0.34% to study the effect of incorporating Sesbania or Vigna legume residues or wheat straw at 15 and 30t ha^?1 on temporal variation in ammoniacal and nitrate‐N in soil under submergence and well drained conditions. Under submergence most mineral N was present as ammoniacal‐N, while under well drained conditions it was present as Nitrate‐N. The content of ammoniacal N in soil was the highest after 30 days of incubation and declined thereafter under submergence. On the other hand under well drained conditions the mineral‐N (mostly nitrate) content in soil at 30 DAI was very little and showed increases only later, reaching the highest level at 90 DAI. Application of wheat straw specially at 301 ha^?1 level resulted in immobilization of native soil‐N. These results show that rice which is grown under submergence can be transplanted soon after incorporation of legume residues, but for wheat or other crops which are grown under well drained condition a time interval of 30 days or more needs to be provided before sowing the crop.     

Influence of moisture regime on inhibition of nitrification by DCD

A laboratory study at the Indian Agricultural Research Institute, New Delhi showed that DCD was an efficient nitrification inhibitor under field capacity moisture (???30 kPa) but not so under submerged soil conditions. Nitrification inhibition by DCD was 79.6% after 1 week of incubation and decreased to 59.3% after 3 weeks of incubation under field capacity moisture, while it was only 19.3% after 1 week of incubation and 10.6% and 18.4% after 2 and 3 weeks of incubation under submergence, respectively. DCD can play an important role in reducing N losses from agricultural fields.     

Assessment of Genetic Diversity of Drought Tolerant and Susceptible Rice Genotypes Using Microsatellite Markers

The introgression of wild chromosomal segments into popular rice varieties is one of the potential approaches for developing varieties for drought stress condition. Sixteen genotypes, including nine indica, two tropical japonica and five chromosome segments substitution lines(CSSLs) with different levels of tolerance/susceptibility to drought stress, were selected for diversity study. Sixty-three microsatellite markers were utilized for assessing genetic diversity. A total of 95 alleles were amplified, and out of them, 60 were polymorphic. Six unique alleles, amplified by the microsatellite loci RM276, RM472,RM488, RM537, RM541 and RM28089, were identified in six genotypes, namely FR13A, Brahamanakhi,RUF44, Swarna-sub1, Brahamanakhi and Satyabhama. The highest genetic similarity was found among CSSLs. Polymorphism information content(PIC) value varied from 0 to 1.00 with an average of 0.66 per locus. Twenty-eight microsatellites were found to be polymorphic, which could be used in marker-assisted selection programme. All the sixteen genotypes were grouped into two major clusters at genetic similarity of 0.64. In the cluster I, five CSSLs identified as diverse genotypes had wild ancestor segments responsible for drought tolerance, and hence they could be utilized as potential donors. The popular Indian varieties, Swarna-sub1 and IR64-sub1, could be used as recurrent parents in the future breeding program for developing varieties for abiotic stresses such as submergence and drought.     

基于FloodArea的天长市“7.24”暴雨过程淹没模拟

基于德国Geomer公司开发的FloodArea水动力淹没模型,结合气象、水文及基础地理信息数据等,对2015年7月24日天长市出现的一次暴雨过程进行淹没模拟。结果表明,模拟淹没情况与实际淹没在时间上有很好的一致性,可为天长市暴雨预警工作提供参考。     

模拟硝田土壤铁和硫的形态转化特征及其影响因素

采用室内培养试验,在确定模拟硝田土壤硫酸钠含量的基础上,观测并探讨落干/淹水状况、有机物质种类与数量对模拟硝田土壤铁和硫形态转化特征的影响。结果表明:全铁(Fet)和游离铁(Fed)受落干/淹水状态和有机物质种类与数量的影响均不显著,而活性铁(Feo)、络合铁(Fep)、亚铁离子(Fe(II))及有效铁(Fea)受淹水及有机物质数量的显著影响,Fe(II)、Fea还受有机物质种类的显著影响;硫形态转化同时受淹水及有机物质种类与数量的影响;土壤铁、硫形态转化一方面通过有机物质与铁、硫的直接作用实现,一方面通过改变土壤氧化还原电位(Eh)及还原性物质总量(TARM)等氧化还原状况实现;铁与硫的形态转化也表现出一定的耦合关系。     

Long-term culture of Atlantic salmon (Salmo salar L.) in submerged cages during winter affects behaviour, growth and condition

In the search for alternative farming methods, we investigated whether large salmon submerged below 10 m in winter conditions behaved normally and performed as well as control fish held in standard surface cages. On average, 2345 salmon of ~ 3.5 kg were kept in each of six 2000 m³ sea-cages for 6 weeks; three of which were submerged to 10–24 m depth and three acted as surface controls (0–14 m). Behaviour during both day and night was studied with echo-sounders, and underwater video cameras fitted with infra-red lamps. A sub-sample of fish from each cage was weighed, measured and assessed for fin and snout condition prior to and after the experimental period. In addition, the vertebral column of 50 fish from the control and submerged treatments were dissected and X-rayed to assess vertebral deformities. The submerged salmon seemed unable to re-fill any gas into the swim bladder, as a linear decrease in echo reflection to < 5% of pre-submergence levels after 22 days of submergence indicated loss of almost all gas from the physostomous swim bladders and negatively buoyant fish. Around day 22, submerged salmon swam at night time with a distinct ‘tail-down, head-up’ tilt (26°) compared to the horizontal swimming position of control fish (− 3°). Average swimming speed (body length per second) of submerged salmon were 1.3–1.4 times faster (day: 0.77 ± 0.02; night: 0.46 ± 0.02, (mean ± SE)) than control fish (day: 0.54 ± 0.01; night: 0.37 ± 0.02) both during day and night. Almost no mortality was seen, and the submerged salmon maintained similar diurnal vertical migrations as the surface fish, indicating that deep submergence did not exhaust the fish. However, submerged fish fed less efficiently, resulting in lower growth and reduced feed utilization. Fins and snouts of the submerged fish had small, but significantly more erosion than the control fish. Vertebrae in the tail region were significantly compressed in the submerged fish compared to control fish. This could be an early symptom of development of vertebral deformities. The results suggest that continuous submergence below 10 m for longer than 2 weeks reduces the welfare and performance of Atlantic salmon.     

Changes in Cell Wall-Bound Phenolic Acids in the Internodes of Submerged Floating Rice

Abstract

Submergence induces rapid elongation of internodes in floating rice (Oryza sativa L.). We examined the distributions of p-coumaric, ferulic and 5-5-coupled diferulic acids ester-linked to cell walls along the axis of highest internodes of submerged and air-grown floating rice stem segments. The amounts of ferulic and 5-5-diferulic acids per cell wall weight were lowest around the intercalary meristem, and increased as the distance from the meristematic zone increased toward the upper part of the internode in both air-grown and submerged stem segments. The ratio of 5-5-diferulic acid to ferulic acid also increased toward the upper, old parts of internodes in both air-grown and submerged stem segments. These observations suggest that the feruloylation of cell wall polysaccharides and the formation of diferulic acids contribute to the cessation of internodal cell elongation and that the formation of diferulic acids in cell walls is controlled by the coupling reaction in addition to the feruloylation. The amounts of p-coumaric acid per unit length and per cell-wall weight were markedly low in the newly elongated region of submerged internodes, and closely correlated with cell-wall dry mass in both air-grown and submerged internodes, suggesting that the deposition of p-coumaric acid in cell walls is related to the formation of secondary cell walls in floating rice internodes.     

香稻育种新材料的抗性基因与表型鉴定

‘大粒香’是著名的香稻品种之一,但对稻瘟病敏感的缺点限制了其推广。本研究利用分子标记YY5-YY8、Bph14P/Bph14N、MS5、Pibdom、Pi-ta、pTA248、Sub1-1,从课题组选育的129株‘大粒香’改良系F4代中筛选同时聚合香味基因badh2,抗褐飞虱基因Bph14和Bph15,抗稻瘟病基因Pita和Pib,抗白叶枯病基因Xa21及耐涝基因Sub1的单株,并从中选择农艺性状较好的单株进行对应基因的表型鉴定,以期获得具有多种抗性的香稻育种新材料。通过PCR技术对改良系F4代的badh2、Bph14、Bph15、Pita、Pib、Xa21和Sub1基因进行分子标记检测,从129个单株中筛选出同时聚合以上7个基因的植株30株,从中选择农艺性状较好的单株17C1389-4-4W进行表型鉴定。咀嚼实验和KOH浸泡-嗅闻实验结果表明17C1389-4-4W具有香味,褐飞虱接种实验结果表明17C1389-4-4W抗褐飞虱级别为3级,稻瘟病菌株Gally接种实验结果表明17C1389-4-4W抗稻瘟病级别为1级,白叶枯菌株PXO86接种试验结果表明17C1389-4-4W抗白叶枯病级别为1级,苗期淹涝实验结果显示17C1389-4-4W耐涝性显著强于亲本。大粒香改良系17C1389-4-4W聚合了多达6个抗性基因,将在多抗香稻育种中发挥重要作用。     

Effect of green manuring (Sesbania aculeata) on zinc equilibria in submerged calcareous and non-calcareous soils

Summary A pot experiment was conducted to study the effect of green manuring (Sesbania aculeata) on pH, electrical conductivity (EC), Zn concentration and ZN equilibria in a calcareous and a non-calcareous soil under submerged conditions. The soil solutions were drawn anaerobically by gravity and analysed for pH, EC and Zn. Green manuring lowered the pH and increased the EC throughout submergence compared with the untreated control. The effect of green manuring was more pronounced in non-calcareous soil. The concentration of water-soluble Zn under submergence alone continued to decline up to the end of the experiment in both soils. But Zn concentration in green manure-amended soil was lower during the initial stages and higher in the later stages in comparison with the unamended soil. Zn potential values in the case of submergence alone were within the range of the ZnCo₃-Zn²⁺ (aq) system up to 1 week and 4 weeks for non-calcareous and calcareous soil, respectively. Thereafter they shifted to those of the Zn-soil (unknown solid phases)-Zn²⁺ (aq) system. Under green manuring the values were within the range of the latter system throughout the experiment.