Effects of different neem preparations in comparison to synthetic insecticides on the whitefly parasitoid Encarsia sophia (Hymenoptera: Aphelinidae) and the predator Chrysoperla carnea (Neuroptera: Chrysopidae) on cotton under laboratory conditions

The contact and feeding toxicity of NeemAzal T/S (EID Parry, Chennai, India) to the parasitoid Encarsia sophia (Girault & Dodd) was compared with three synthetic insecticides (chlorpyriphos, endosulfan and triazophos) against immatures and adult emergence. NeemAzal T/S (1.0%) at lower dose (200 mg/l) did not cause any effect on the emergence of E. sophia adults, but there was a significant reduction in emergence at higher doses (800 mg/l). Also, it did not show contact toxicity to adults of E. sophia, but there was a significantly high feeding mortality in a dosage dependant manner, whereas chlorpyriphos, endosulfan and triazophos showed high toxicity both by contact and feeding method. Three neem preparations registered in India, NeemAzal T/S, Nimbecidine (T. Stains, Coimbatore) and Godrej Achook (Godrej Agrovet, Mumbai) were tested against egg and larval stages of Chrysoperla carnea (Stephens) at three dosages, using a synthetic insecticide, triazophos 40 EC (200 mg/l), for comparison under laboratory conditions. The three biorationals did not induce any adverse effect on the hatchability of C. carnea eggs. The mortality of the first instars of C. carnea was not affected by any of the azadirachtin enriched formulations; however, at higher dosage of 800 mg/l these neem based products resulted in increased mortality of the first and second instar larvae of C. carnea relative to the untreated controls. Whereas, triazophos induced very high mortality rates (85.0, 89.0 and 81.5%) of all the three larval instars. The neem based insecticides showed a dosage-dependant effect on the larval instars of C. carnea. Thus, these biorationals show that there is a potential to use them in an IPM system, being safe for natural enemies of B. tabaci in cotton.     

Mechanisms and diversity of resistance to sorghum shoot fly,Atherigona soccata

Sorghum shoot fly, Atherigona soccata, is one of the important pests of postrainy season sorghums. Of the 90 sorghum genotypes evaluated for resistance to this pest, RHRB 12, ICSV 713, 25026, 93046 and 25027, IS 33844‐5, Giddi Maldandi and RVRT 3 exhibited resistance in postrainy season, while ICSB 463, Phule Anuradha, RHRB 19, Parbhani Moti, ICSV 705, PS 35805, IS 5480, 5622, 17726, 18368 and 34722, RVRT 1, ICSR 93031 and Dagidi Solapur showed resistance in rainy season, suggesting season‐specific expression of resistance to A. soccata. ICSB 461, ICSB 463, Phule Yasodha, M 35‐1, ICSV 700, 711, 25010, 25019 and 93089, IS 18662, Phule Vasudha, IS 18551 and 33844‐5 and Barsizoot had fewer deadhearts than plants with eggs across seasons, suggesting antibiosis as one of the resistance mechanism. Five genotypes exhibited resistance with high grain yield across seasons. Correlation, path and stepwise regression analyses indicated that leaf glossiness, seedling vigour, trichome density, oviposition and leaf sheath pigmentation were associated with the expression of resistance/susceptibility to shoot fly, and these can be used as marker traits to select and develop shoot fly‐resistant sorghums.     

Variability and selection on different <Emphasis Type="Italic">Argyrolobium roseum</Emphasis> accessions for morphological traits and yield

Variability studies were carried out among different accessions of Argyrolobium roseum for 12 metric traits under natural and cultivated conditions. Almost all characters showed higher values in cultivated than natural population. Leaf breadth recorded highest CV (30.59%). Highest percentage of vitexin and D-pinitol (0.208 and 0.773% dwb) was observed in RAR-7 and RAR-6, respectively, under cultivated conditions. Phenotypic coefficient was higher than genotypic coefficient of variation. The association analysis revealed that root yield had positive significant correlation with 100 seed weight (r=0.839) biomass yield (r=0.601), where biomass yield had a positive significant correlation with leaf length, single pod weight. High heritability (97.4–99.8%) coupled with moderate genetic advance ranged between (49–67%) as a percent of mean was observed for leaf breadth, pod length, total foliage biomass yield and total root yield/plant. This suggests that direct selection for these traits is suitable for the improvement of this crop.     

印度拉贾斯坦邦半干旱地区流域发展项目对农业经济的影响

从 2 0世纪 70年代就开始的科学研究已经充分论证了改良土壤湿度和提高农业科技含量 (改良种子 ,增施化肥 )导致作物产量的提高 ,不仅可在宏观上维持全面的农产品供应 ,而且还可维持大部分农村家庭的经济收入。因此保持雨水、防治土壤侵蚀成为发展干旱地区农业的中心议题。因为     

Puddling and N management effects on crop response in a rice-wheat cropping system

Coarse-textured soils are puddled to reduce high percolation losses of irrigation water under rice (Oryza sativa L.). This practice, however, reduces yield of succeeding wheat (Triticum aestivum L.) owing to deterioration in soil physical conditions. The 6 year field study reported in this paper evaluated the effects of puddling level and integrated N management on the development of subsurface compaction and growth and yield of rice and the following spring wheat grown in 1 year sequence on a sandy loam soil. Treatments were combinations of three puddling levels: low (one discing and one planking), medium (two discings and one planking), and high (four discings and one planking), and three nitrogen sources: (1) 120 kg N ha⁻¹ from urea, (2) 60 kg N ha⁻¹ from urea plus sesbania (Sesbania aculeata Pers.) green manure, and (3) 60 kg N ha⁻¹ from urea plus 20 Mg ha⁻¹ farmyard manure. Percolation rate decreased from 14 mm day⁻¹ with low puddling to 10 mm day⁻¹ with high puddling, with a corresponding reduction in irrigation water requirement of rice of about 20%. Bulk density profiles in the 0–30 cm soil layer showed the formation of a compact layer at 15–20 cm depth, and bulk density increased with puddling level and cropping season. The impact of organic amendments in reducing bulk density was immediate, but the rate of increase in bulk density with time was the same in all the nitrogen sources. Organic amendments did not affect percolation rate and irrigation requirement of rice. Rice yields were not significantly affected by puddling and N source treatments throughout the study period. Residual effects of treatments on wheat yield were observed from the second season onwards. Interactive effects of puddling and N source on yields of rice and succeeding wheat were not significant. Yield differences in wheat between high and low puddling were 8% and 11% during the second and the fifth cropping season, respectively. This study indicates that medium puddling was optimum, as it reduced percolation without decreasing yield of succeeding wheat.     

Molecular simulations to estimate thermodynamics for adsorption of polar organic solutes to montmorillonite

Ideally, one could use molecular mechanics or quantum mechanics to predict the magnitude of organic solute adsorption from water to soil minerals. Reproduction and/or prediction of mineral and interfacial structures remains challenging, but calculation of meaningful energy relations through computational chemistry techniques is even more difficult than structural calculations. This paper attempts to define the necessary and relevant components for an overall scheme that allows translation of computed interaction enthalpies to experimental adsorption enthalpies and vice versa. While the scheme could be applied to quantum calculations, we test it for the possibility of using empirical molecular mechanics to estimate relative energies for the adsorption of non‐ionic organic solutes in clay mineral‐water‐solute systems. We used molecular dynamics’ simulations to estimate relative clay–organic interaction enthalpies for a series of nitro‐aromatic solutes and hydrated, K‐saturated montmorillonite, for comparison with experimental adsorption isotherm data for the same clay‐nitroaromatic systems. The trend of computed interaction enthalpies (e.g. −234 ± 17 kJ mol⁻¹ for trinitrobenzene and −154 ± 16 kJ mol⁻¹ for p‐nitrobenzene) agreed modestly well with the trend of adsorption maxima from the experiments. Furthermore, we developed several variants on a thermodynamic cycle framework for comparing computed interaction energies with experimentally determined adsorption enthalpies. The algorithms, which include estimates for enthalpy changes both in bulk solution and in the clay interlayer, show promise: for p‐dinitrobenzene and for 1,3,5‐trinitrobenzene, the overall predicted adsorption enthalpies (e.g. −13 ± 22 and −67 ± 23 kJ mol⁻¹, respectively) were in modest agreement with experiments (−18 ± 1 and −28 ± 4 kJ mol⁻¹, respectively). We discuss shortcomings of the methods, in hopes of encouraging better estimates for the various energy terms, improvement of the algorithms, and more valid comparisons between quantum mechanical or molecular mechanical interaction energies and experimental enthalpies.     

Ascaridia galli: effect of some anthelmintics on amino acid uptake and macromolecular synthesis in vitro.

L-(U-14C) aspartic acid, L-(U-14C) alanine and L-(U-14C) leucine uptake by Ascaridia galli was found to be a non-linear function of time and limiting substrate concentration. The uptake was rapid initially but achieved steady state thereafter, possibly owing to the saturation of transport loci. Linear transformations of substrate saturation kinetics by Lineweaver-Burk plots of L-(U-14C) aspartic acid, L-(U-14C) alanine and L-(U-14C) leucine gave Kt values of 4.76, 3.03 and 2.0 mM and Jmax of 5.0, 3.57 and 2.08 m moles/100 mg dry weight/2 min, respectively. D1-tetramisole and 1-tetramisole (levamisole) inhibited the uptake of amino acids. The uptaken amino acids were readily metabolized into different tissue fractions. D1-tetramisole and levamisole significantly inhibited the incorporation of the three amino acids into the nematode's total protein, RNA and lipid fractions in an in vitro incubation system.     

Lipid metabolism and low molecular weight solute uptake in Ascaridia galli

Adult Ascaridia galli, an intestinal nematode parasite of fowl, reveals a large variety of complex lipids such as phospholipids containing choline, ethanolamine, inositol, serine and glycerol. Lysophospholipid species, vinyl ether phospholipid (plasmalogen), neutral acylglycerols, cholesterol and non-esterified fatty acids are also present. Sugar-containing lipids, such as cerebrosides, sulphatides and gangliosides are abundantly present. Female parasites contain more lipids, particularly acylglycerols and phospholipids. Acylglycerols, phosphatidyl choline, phosphatidyl ethanolamine and glycolipids incorporate a large amount of radiolabelled precursor substrate in A. galli. The presence of important enzymes of lipid biosynthesis like glucose-6-phosphate dehydrogenase, malate dehydrogenase and hydroxymethyl glutaryl-CoA reductase as well as an enzyme of lipid ester hydrolysis, triacylglycerol lipase is detected in the parasite. These enzymes show subcellular distribution patterns and Michaelis-Menten kinetic characteristics comparable with that from rat liver homogenate. Studies on the uptake of labelled precursor molecules for lipid biosynthesis, glucose, acetate and palmitate show that the parasites can take up the isotopes readily in a time-dependent manner, showing substrate saturation kinetics, dependence upon Na ions, and can be inhibited by the presence of the bile salts sodium cholate and sodium deoxycholate. The substrate affinity constant (Kt) and maximum apparent velocity of glucose uptake in A. galli were found to be 9.09 mM and 26.67 mM per 100 mg tissue dry weight per min at 37 degrees C.     

Cumulative effects of tree-based intercropping on arbuscular mycorrhizal fungi

In tree-based intercropping system (agroforestry), the role of perennial trees in maintaining active populations and mycelial networks of arbuscular mycorrhizal fungi (AMF) is well documented. Agroforestry positively influences the AMF community, but complete studies regarding mycorrhization in such systems are scarce. The present study was conducted to assess the effect of tree introduction in agriculture fields on mycorrhization. In particular, we investigated the effect of trees on AMF colonization of intercrops and vice versa, the effect of canopy management of trees on their root colonization, and the cross-infectivity of AMF isolated from tree rhizosphere in intercrops and vice versa. The results of the field study suggest that in agroforestry systems, trees acted as AMF inoculum reservoir for intercrops, especially during the rainy season. Intercropping (Phaseolus mungo and Triticum aestivum in the rainy and winter seasons, respectively) increased mycorrhization, i.e., root colonization and spore population in the rhizosphere of Albizia procera and Eucalyptus tereticornis. Canopy management, i.e., shoot pruning, reduces root colonization in A. procera, Anogeissus pendula, Dalbergia sissoo, Hardwickia binata, and Tectona grandis, especially in April 2005 (late spring), but during subsequent periods, differences among the treatments were at par. Results from greenhouse suggest that AMF are nonspecific in their selection of host since species isolated from tree rhizosphere could colonize the roots of crops and vice versa.