Identification of drought responsive QTLs during vegetative growth stage of rice using a saturated GBS-based SNP linkage map

Drought is a major abiotic constraint for rice production worldwide. The quantitative trait loci (QTLs) for drought tolerance traits identified in earlier studies have large confidence intervals due to low density linkage maps. Further, these studies largely focused on the above ground traits. Therefore, this study aims to identify QTLs for root and shoot traits at the vegetative growth stage using a genotyping by sequencing (GBS) based saturated SNP linkage map. A recombinant inbred line (RIL) population from a cross between Cocodrie and N-22 was evaluated for eight morphological traits under drought stress. Drought was imposed to plants grown in 75 cm long plastic pots at the vegetative growth stage. Using a saturated SNP linkage map, 14 additive QTLs were identified for root length, shoot length, fresh root mass, fresh shoot mass, number of tillers, dry root mass, dry shoot mass, and root-shoot ratio. Majority of the drought responsive QTLs were located on chromosome 1. The expression of QTLs varied under stress and irrigated condition. Shoot length QTLs qSL1.38 and qSL1.11 were congruent to dry shoot mass QTL qDSM1.38 and dry root mass QTL qDRM1.11, respectively. Analysis of genes present within QTL confidence intervals revealed many potential candidate genes such as laccase, Calvin cycle protein, serine threonine protein kinase, heat shock protein, and WRKY protein. Another important gene, Brevis radix, present in the root length QTL region, was known to modulate root growth through cell proliferation and elongation. The candidate genes and the QTL information will be helpful for marker-assisted pyramiding to improve drought tolerance in rice.     

Soil infiltration, runoff and sediment yield from a shallow soil with varied stone cover and intensity of rain

Stones on the surface of the soil enhance infiltration and protect the soil against erosion. They are often removed in modern mechanized agriculture, with unfortunate side‐effects. We evaluated experimentally the influence of surface stones on infiltration, runoff and erosion under field conditions using a portable rainfall simulator on bare natural soil in semi‐arid tropical India, because modernization and mechanization often lead to removal of these stones in this region. Four fields with varied cover of stones from 3 to 65% were exposed to three rainfall intensities (48.5, 89.2 and 136.8 mm hour^?1). Surface stones retarded surface runoff, increased final infiltration rates, and diminished sediment concentration and soil loss. The final infiltration ranged from 26 to 83% of rainfall when the rainfall intensity was 136.8 mm hour^?1. The reduction in runoff and soil erosion and increase in infiltration were more pronounced where stones rested on the soil surface than where they were buried in the surface layer. The sediment yield increased from 2 g l^?1 for 64.7% stone cover with rainfall of 48.5 mm hour^?1 to 70 g l^?1 for 3.5% stone cover with rain falling at 136.8 mm hour^?1. The soil loss rate was less than 2 t ha^?1 hour^?1 for the field with stone cover of 64.7% even when the rainfall intensity was increased to 136.8 mm hour^?1. The effects of stones on soil loss under the varied rainfall intensities were expressed mathematically. The particles in the sediment that ran off were mostly of silt size.     

Molybdenum status and critical limit in the soil for green gram (Vigna radiata) growing in Madurai and Sivagangai districts of Tamil Nadu,India

Abstract

The decay of rice residue was investigated after incubation periods of from 1 to 24 months at 30°C under both flooded and upland soil conditions. Tops and roots of rice plants were cut into about 10-mm length, and separately incorporated in soil which had been passed through a 0.5-mm sieve. Plant debris were fractionated physically according to their sizes and divided into five groups (>4 mm, 4-2 mm, 2-1 mm, 1-0.5 mm, and 0.5-0.25 mm).

Carbon loss from the soils amended with rice residues and decrease in the weight of total plant debris proceeded at a rapid speed in the early periods (around 4 months) and then at a slow speed in the subsequent periods under both flooded and uplana soil conditions. The distribution of the plant debris in the decomposition processes differed under flooded and upland conditions. Under flooded conditions, 2–4 mm-sized plant debris were retained for a long period with slow transformation into the smaller fractions. In contrast, under upland conditions, change of plant debris from large to small size fractions proceeded gradually. This continuous change could be attributed to the high decomposing activities of fungi under upland conditions.     

Priority habitats for the conservation of large river fish in the Ganges river basin

• 1. Three classes of habitat used by groups of fish species classified as conservation and management priorities were developed for the Gerua River (also known as the Girwa River, Karnali River) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m³ s^?1, up to 900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversions and river alterations.
• 2. Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for 2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of the river habitats were grouped to identify classes of river habitat for conservation.
• 3. Most species and life‐stage groups specialized on specific habitat conditions revealed by multivariate analyses of variance and a principal component analysis. The most numerous and diverse group (six species, 15 life stages) was associated with deep depositional habitats with sandy substrate. Two species covering three life stages were primarily oriented to erosional habitat marked by fast current velocity with pebble and cobble substrate. A third group of three species of adults and juveniles were intermediate in habitat use.
• 4. River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel‐forming functions.

Copyright © 2006 John Wiley & Sons, Ltd.     

Soil degradation and mitigation in agricultural lands in the Indian Anthropocene

Current widespread and intensive soil degradation in India has been driven by unprecedented levels of population growth, large-scale industrialization, high-yield agriculture, urban sprawl and the spread of human infrastructure. The damage caused to managed and natural systems by soil degradation threatens livelihoods and local services and leads to national socio-economic disruption. Human-induced soil degradation results from land clearing and deforestation, inappropriate agricultural practices, improper management of industrial effluents and wastes, careless management of forests, surface mining, urban sprawl, and ill-planned commercial and industrial development. Of these, inappropriate agricultural practices, including excessive tillage and use of heavy machinery, over-grazing, excessive and unbalanced use of inorganic fertilizers, poor irrigation and water management techniques, pesticide overuse, inadequate crop residue and/or organic carbon inputs, and poor crop cycle planning, account for nearly 40% (121 Mha) of land degradation across India. Globally, human activities related to agriculture contribute to the transgression of four of the nine Planetary Boundaries proposed by Rockström et al. (2009): Climate Change, Biodiversity Integrity, Land-system Change, and altered Phosphorus and Nitrogen Biogeochemical Flows. This review focuses on how knowledge of soil processes in agriculture has developed in India over the past 10 years, and the potential of soil science to meet the objectives of the United Nations' Sustainable Development Goal 2: Zero Hunger (End hunger, achieve food security, improved nutrition and promote sustainable agriculture), using the context of the four most relevant Planetary Boundaries as a framework. Solutions to mitigate soil degradation and improve soil health in different regions using conservation agricultural approaches have been proposed. Thus, in this review we (1) summarize the outputs of recent innovative research in India that has explored the impacts of soil degradation on four Planetary Boundaries (Climate Change, Biodiversity Loss, Land-system Change, and altered Biogeochemical Flows of Phosphorus and Nitrogen) and vice-versa; and (2) identify the knowledge gaps that require urgent attention to inform developing soil science research agendas in India, to advise policy makers, and to support those whose livelihoods rely on the land.     

Trait phenotyping and SSR markers characterization of wheat (Triticum aestivum L.) germplasm for breeding early maturing wheat’s for Western-Himalayas

Genetic Resources and Crop Evolution - The study involved evaluation of 96 wheat genotypes for early maturity and related traits and molecular characterization of trait specific candidate genotypes...     

Hyperaccumulative Characteristics of Weed Species to Heavy Metals

Phytoremediation, which mainly employs hyperaccumulators to remove heavy metals from contaminated soils, is receiving more attention world-wide. The identification of hyperaccumulators is still a key step for phytoremediation. This research is devoted to identify some plants with hyperaccumulative characteristics from weed species. In a pot culture experiment, the hyperaccumulative characteristics of 13 weed species in 11 families to Cd, Pb, Cu and Zn were examined. The result showed that Taraxacum mongolicum and Rorippa globosa indicated some Cd hyperaccumulative properties. In a sample-analysis experiment conducted in a Pb?Zn mining area, T. mongolicum and R. globosa also displayed the same hyperaccumulative characteristics. However, in a concentration gradient experiment, Cd content in shoot of T. mongolicum was not higher than 100 mg/kg (DW, dry weight), the minimum Cd concentration for a Cd-hyperaccumulator in any treatment. The concentration of Cd in the stems and leaves of R. globosa were greater than 100 mg/kg, under the conditions of the soils spiked with 25 and 50 mg/kg Cd. The Cd accumulation factors and translocation factors in the shoots of R. globosa were higher than 1 too, and the plant biomasses did not decrease significantly (p?<?0.05) compared with the control. Thus, we conclude that only R. globosa showed the whole Cd-hyperaccumulator properties, which is a Cd-hyperaccumulator.     

A Comparison of Diffusion-Conductimetric and Distillation-Titration Methods in Analyzing Ammonium- and Nitrate-Nitrogen in the KCl-Extracts of Georgia Soils

Soil mineral (or inorganic) nitrogen (SMN), which primarily exists as exchangeable and soluble ammonium (NH4⁺) and the nitrate (NO₃^?) ions, represents readily available nitrogen for plant growth. Over the years a 2M potassium chloride (KCl) solution has become the extraction solution of choice for extracting SMN. In the research and service laboratories, either distillation-titration method (DTM) or colorimetric method (CM) is virtually the standard to measure NH₄⁺- and NO₃^?-N in the 2M KCl soil extracts. However, being a time-consuming and labor intensive method, DTM generally has a very low throughput. Likewise, CM is affected by interferences from pH variation, color, turbidity, presence of organic species, and some other constituents in the extracts. In contrast, diffusion conductivity method (DCM) is a less expensive and high throughput one, which is also relatively free from common interferences. In this study, we, therefore, compared the extraction efficiency of various KCl concentrations and performance of diffusion conductivity method (DCM) with DTM in measuring NH₄⁺-N and NO₃^?-N in KCl extracts of 32 agricultural soils of Georgia. A 0.2M KCl solution extracted statistically similar amounts of NH₄⁺-N and NO₃^?-N as did 2M KCl, suggesting that a 10-fold dilute KCl solution than the standard 2M KCl might be good enough to extract and estimate the most of SMN. For the analyses of NH₄⁺- and NO₃^?-N in the KCl extracts, the DCM produced results statistically similar to those produced by DTM. The deviation between the results given by DCM and DTM was no more than ±10%. Thus, DCM appears to be an attractive alternative to the labor intensive and time-consuming DTM for measuring NH₄⁺- and NO₃^?-N in the KCl extract of soils in the research and service laboratories.     

Removal of As(III) from Aqueous Solution Using Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles: Process Modeling and Optimization Using Statistical Design

In this study, Extran (biodegradable surfactant) was used for the preparation of Fe₃O₄ nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe₃O₄ nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe₃O₄ nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe₃O₄ nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.