Arbuscular Mycorrhizal (AM) Diversity in Prosopis cineraria (L.) Druce Under Arid Agroecosystems

Arbuscular mycorrhizal (AM) fungi associated with Prosopis cineraria (Khejri) were assessed for their qualitative and quantitative distribution from eight districts of Rajasthan. A total of three species of Acaulospora, one species of Entrophospora, two species of Gigaspora, twenty-one species of Glomus, seven species of Sclerocystis and three species of Scutellospora were recorded. A high diversity of AM fungi was observed and it varied at different study sites. Among these six genera, Glomus occurred most frequently. Glomus fasciculatum, Glomus aggregatum, and Glomus mosseae were found to be the most predominant AM fungi in infecting Prosopis cineraria. Acaulospora, G. fasciculatum, Sclerocystis was found in all the fields studied, while Scutellospora species were found only in few sites. A maximum of thirty-six AM fungal species were isolated and identified from Jodhpur, whereas only thirteen species were found from Jaisalmer. Spores of Glomus fasciculatum were found to be most abundant under Prosopis cineraria.     

Phosphorus requirement of Catla (Catla catla Hamilton) fingerlings based on growth, whole-body phosphorus concentration and non-faecal phosphorus excretion

A 120‐day feeding trial was conducted to determine the dietary requirement of phosphorus for Indian major carp, catla (Catla catla) fingerlings. Four hundred and eighty fingerlings (mean body weight: 4.23±0.87 g) were randomly distributed among eight treatment groups with three replicates each. Eight isonitrogenous and isocaloric semi‐purified diets (crude protein: 35% and crude lipid: 8.5%) were formulated with graded levels of phosphorus using KH₂PO₄ (T₁: control, 0.1%; T₂: 0.3%; T₃: 0.5%; T₄: 0.7%; T₅: 0.9%; T₆: 1.1%; T₇: 1.3%; T₈: 1.5%) and fed to the respective groups. Twenty fish were stocked in 150 L plastic tanks and fed to apparent satiation twice a day. Specific growth rate (SGR) significantly (P<0.05) increased with increasing dietary phosphorus concentration from 0.73% to 1.27%, after which there was a slight decline in growth at 1.1% available phosphorus (aP) and remained constant thereafter. The quadratic broken‐line model based on growth was Y=317.5?581(0.64?x) (0.64?x); R²=0.73. Moisture and crude protein contents of whole body were similar among all the treatments. However, the ether extract in T₁ group was significantly (P<0.05) higher than all the other treatments. The whole‐body phosphorus content increased significantly (P<0.05) with an increase in phosphorus in the diets. The one‐slope broken‐line model based on whole‐body phosphorus concentration was Y=4.07?1.63 (0.71?x); R²=0.48. The one‐slope broken‐line model for non‐faecal phosphorus excretion as inorganic phosphorus (Pi) for 24 h revealed a trend of Y=12.67+73.96 (x?0.6); R²=0.81. Minimum aP requirements based on weight gain (%), whole‐body phosphorus content and phosphorus excretion were 0.64%, 0.71% and 0.6%, respectively. Hence, the dietary aP requirement of catla fingerlings ranges from 0.6% to 0.71%.     

Limited evidence for genetic variation for resistance to the white spot syndrome virus in Indian populations of Penaeus monodon

There has been a highly detrimental impact of the white spot syndrome virus (WSSV) on black tiger shrimp (Penaeus monodon) aquaculture in India. Currently, no cost‐effective measures are available for controlling the disease. One alternative is to improve WSSV resistance through a selective breeding programme for disease‐resistant shrimp, provided that genetic variation exists for this trait. The aim of this study was to evaluate the evidence for genetic variation in resistance to WSSV in P. monodon sourced from Indian populations. Post‐larval shrimp (n=1950) from 54 full‐sibling families were challenged with WSSV using WSSV‐infected mince meat. The heritability was estimated using four different statistical models fitted to the resulting time to death data, including two linear models and two Weibull proportional hazard frailty models. None of the estimated heritabilities were significantly different from zero. We suggest three possible explanations for these results: there actually is very little variation between P. monodon in WSSV resistance and all individuals are highly susceptible to the disease; there is genetic variation in resistance to WSSV in P. monodon but we did not find it in our experiment because the level of challenge in the experiment was too high to allow genetic differences to be expressed; the variation is due to mutations conferring resistance, which are at a low frequency in the population, and we did not sample a broad enough genetic base to capture these mutations.     

Hydrocarbon separations in a metal-organic framework with open iron(II) coordination sites

The energy costs associated with large-scale industrial separation of light hydrocarbons by cryogenic distillation could potentially be lowered through development of selective solid adsorbents that operate at higher temperatures. Here, the metal-organic framework Fe(2)(dobdc) (dobdc(4-) : 2,5-dioxido-1,4-benzenedicarboxylate) is demonstrated to exhibit excellent performance characteristics for separation of ethylene/ethane and propylene/propane mixtures at 318 kelvin. Breakthrough data obtained for these mixtures provide experimental validation of simulations, which in turn predict high selectivities and capacities of this material for the fractionation of methane/ethane/ethylene/acetylene mixtures, removal of acetylene impurities from ethylene, and membrane-based olefin/paraffin separations. Neutron powder diffraction data confirm a side-on coordination of acetylene, ethylene, and propylene at the iron(II) centers, while also providing solid-state structural characterization of the much weaker interactions of ethane and propane with the metal.     

Effects of glyphosate on soil microbial communities and its mineralization in a Mississippi soil

Transgenic glyphosate-resistant (GR) soybean [Glycine max (L.) Merr.] has enabled highly effective and economical weed control. The concomitant increased application of glyphosate could lead to shifts in the soil microbial community. The objective of these experiments was to evaluate the effects of glyphosate on soil microbial community structure, function and activity. Field assessments on soil microbial communities were conducted on a silt loam soil near Stoneville, MS, USA. Surface soil was collected at time of planting, before initial glyphosate application and 14 days after two post-emergence glyphosate applications. Microbial community fatty acid methyl esters (FAMEs) were analyzed from these soil samples and soybean rhizospheres. Principal component analysis of the total FAME profile revealed no differentiation between field treatments, although the relative abundance of several individual fatty acids differed significantly. There was no significant herbicide effect in bulk soil or rhizosphere soils. Collectively, these findings indicate that glyphosate caused no meaningful whole microbial community shifts in this time period, even when applied at greater than label rates. Laboratory experiments, including up to threefold label rates of glyphosate, resulted in up to a 19% reduction in soil hydrolytic activity and small, brief (<7 days) changes in the soil microbial community. After incubation for 42 days, 32-37% of the applied glyphosate was mineralized when applied at threefold field rates, with about 9% forming bound residues. These results indicate that glyphosate has only small and transient effects on the soil microbial community, even when applied at greater than field rates.     

Foliar washoff potential and simulated surface runoff losses of trifloxysulfuron in cotton

The surface runoff potential of trifloxysulfuron {N-[(4,6-dimethoxy-2-pyrimidinyl)carbamoyl]-3-(2,2,2-trifluoroethoy)-pyridin-2-sulfonamide sodium salt} in cotton (Gossypium hirsutum L.) production systems has not been evaluated. The objectives of this study were to (i) determine sorption/desorption coefficients for trifloxysulfuron; (ii) quantify foliar washoff of trifloxysulfuron when applied to cotton at the five-leaf stage; and (iii) determine the surface runoff potential of trifloxysulfuron when applied to cotton at the five-leaf stage and to bare soil. Freundlich sorption and desorption coefficients were 1.15 and 1.22, respectively. Sorption data indicated that trifloxysulfuron was moderately sorbed to soil and that it will be transported primarily in the dissolved phase of surface runoff. Foliar washoff studies revealed that approximately 91% of trifloxysulfuron applied to cotton at the five-leaf stage was available for washoff 72 h after application. Simulated rainfall (7.5 cm h-1) applied 1 day after herbicide application (7.9 g ha-1) resulted in average concentrations of trifloxysulfuron in surface runoff water of 0.8 microg L-1 for bare plots and 1.3 microg L-1 for cotton plots. Cumulative trifloxysulfuron losses in surface runoff from bare plots and cotton plots were 0.13 and 0.21 g ha-1, respectively. These values correspond to fractional losses of 1.7% for bare plots and 2.7% for cotton plots. Greater runoff losses of trifloxysulfuron from cotton plots were attributed to foliar washoff. Trifloxysulfuron runoff losses may be curtailed if the herbicide is applied early postemergence when canopy coverage is minimal, thereby reducing the potential for foliar washoff.     

Molecular properties as descriptors of octanol-water partition coefficients of herbicides

Molecular modeling techniques were used to establish relationships between the octanol/water partition coefficient (K _ow) and molecular properties of 90 herbicides with several types of chemistry. The K_ow values were obtained from the literature. Various molecular properties were calculated by quantum mechanical methods using molecular modeling software. The quantitative structure activity relationship (QSAR) analysis of all herbicides showed that K _ow was dependent on bulk (van der Waals volume, VDW_v) and electronic (dipole moment, µ; superdelocalizability of highest occupied molecular orbital, SHOMO; nucleophilic superdelocalizability, SN) properties, and the model explained 68% of the variation in K _ow. Herbicides were broadly divided into six families (ureas, acid amides, triazines, carbamates, diphenyl ethers, and dinitroanilines) based on structural similarities, and separate equations were established for each group. The QSAR models accounted for 74 to 98% of the variation in K _ow within these six groups. Applicability of these models was tested for some herbicides. The QSAR models produced estimates that correlate well with experimental values and appear to be specific to structurally similar compounds.     

Aminomethylphosphonic acid, a metabolite of glyphosate, causes injury in glyphosate-treated, glyphosate-resistant soybean

Glyphosate-resistant (GR) soybean [Glycine max (L.) Merr.] was developed by stable integration of a foreign gene that codes insensitive enzyme 5-enolpyruvylshikimate-3-phosphate synthase, an enzyme in the shikimate pathway, the target pathway of glyphosate. Application of glyphosate to GR soybean results in injury under certain conditions. It was hypothesized that if GR soybean is completely resistant to the glyphosate, injury could be caused by a metabolite of glyphosate, aminomethylphosphonic acid (AMPA), a known phytotoxin. Glyphosate and AMPA effects on one- to two-trifoliolate leaf stage (16-18-days old) GR and non-GR soybean were examined in the greenhouse. In GR soybean, a single application of glyphosate-isopropylammonium (1.12-13.44 kg/ha) with 0.5% Tween 20 did not significantly reduce the chlorophyll content of the second trifoliolate leaf at 7 days after treatment (DAT) or the shoot dry weight at 14 DAT compared with Tween 20 alone. A single application of AMPA (0.12-8.0 kg/ha) with 0.5% Tween 20 reduced the chlorophyll content of the second trifoliolate leaf by 0-52% at 4 DAT and reduced shoot fresh weight by 0-42% at 14 DAT in both GR and non-GR soybeans compared with Tween 20 alone. AMPA at 0.12 and 0.50 kg/ha produced injury in GR and non-GR soybean, respectively, similar to that caused by glyphosate-isopropylammonium at 13.44 kg/ha in GR soybean. AMPA levels found in AMPA-treated soybean of both types and in glyphosate-treated GR soybean correlated similarly with phytotoxicity. These results suggest that soybean injury to GR soybean from glyphosate is due to AMPA formed from glyphosate degradation.     

Expansion of urban area and wastewater irrigated rice area in Hyderabad,India

The goal of this study was to investigate land use changes in urban and peri-urban Hyderabad and their influence on wastewater irrigated rice using Landsat ETM + data and spectral matching techniques. The main source of irrigation water is the Musi River, which collects a large volume of wastewater and stormwater while running through the city. From 1989 to 2002, the wastewater irrigated area along the Musi River increased from 5,213 to 8,939 ha with concurrent expansion of the city boundaries from 22,690 to 42,813 ha and also decreased barren lands and range lands from 86,899 to 66,616 ha. Opportunistic shifts in land use, especially related to wastewater irrigated agriculture, were seen as a response to the demand for fresh vegetables and easy access to markets, exploited mainly by migrant populations. While wastewater irrigated agriculture contributes to income security of marginal groups, it also supplements the food basket of many city dwellers. Landsat ETM + data and advanced methods such as spectral matching techniques are ideal for quantifying urban expansion and associated land use changes, and are useful for urban planners and decision makers alike.     

Linking physical, economic and institutional constraints of land use change and forest conservation in the hills of Nepal

This paper analyses the changes in spatial patterns of agricultural land use during the period 1976–2000 along the altitudinal gradients in a watershed in Nepal. Land change patterns during this period were examined using information on land use derived from satellite images from 1976, 1990 and 2000. During the 24-year period from 1976 to 2000 agricultural land use increased by 35% at a cost of loss of forestland. Agricultural expansion was most conspicuous at higher elevations (1150–2000-m). About 36%, 18% and 6% of forestland was converted into agricultural activities from higher, middle and lower elevations respectively in the period from 1990 to 2000. Spatial distribution of living standard parameters, including farm family income and, food availability obtained from family surveys, shows a decreasing trend as the elevation increases whereas percentage of food bought shows an increasing trend. In this way it was found that, lost forest areas were smaller when located around high-income areas with good quality agricultural land and near an administrative centre as compared to areas located around low-income areas with low quality agricultural land and far from an administrative centre. Additionally, a regression model is constructed, to link the socioeconomic variables with the conversion of forestland into agricultural activities, breaking the study area into smaller zones. The spatial trajectories of these zones are then contrasted, paying particular attention to the socioeconomic conditions and institutional arrangements governing access to land resources. The study finds that while overall land change patterns in the region are largely explained by elevation and the socioeconomic conditions of people living adjacent to the forestland, more specifically, in sub-regional areas, trajectories reflect the signatures of institutions governing access to land. As sustainability of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from agriculture for local people together with loss of ecosystem services.