Biopolymeric superabsorbent hydrogels enhance crop and water productivity of soybean-wheat system in Indo-Gangetic plains of India.

Environmental crises, declining factor productivity, and shrinking natural resource is a threat to global agricultural sustainability. The task is much more daunting in the Indo-Gangetic northern plains of India, where depletion of the underground water table and erratic rains due to the changing climate pose a major challenge to agriculture. To address these challenges a field investigation was carried out during 2016-2018 to test the efficacy of biopolymeric superabsorbent hydrogels namely Pusa Hydrogel (P-hydrogel: a semi-synthetic cellulose derivative-based product) and kaolin derivative of Pusa Hydrogel (K-hydrogel: semi-synthetic cellulose derivative) to assess their effect on crop and water productivity, soil moisture, root dynamics, and economics of soybean (Glycine max L.)-wheat (Triticum aestivum L.) system under three irrigation regimes namely full irrigation, limited irrigation and rainfed. The results revealed that the full irrigation along with P-hydrogel led to enhanced grain yield, biomass yield, and water productivity (WP) of soybean (1.61-10.5%, 2.2-9.5%, and 2.15-21.8%, respectively) and wheat (11.1-18.3%, 12-54% and 11.1-13.1%, respectively) over control plots. Likewise, under water stressed plots of rainfed conditions with P-hydrogel exhibited 52.7 and 20.6% higher system yields (in terms of wheat equivalent yield) over control and other combinations during the respective study years. Whereas the magnitude of increase in system yield under limited irrigation with P-hydrogel was ~ 15.1% and under full irrigation with P-hydrogel was 8.0-19.4%. Plots treated with P-hydrogel retained 3.0-5.0% higher soil moisture compared to no-hydrogel plots, while K-hydrogel treated plots held the lower moisture (4.0-6.0%) than the control. In terms of profitability, full irrigation along with P-hydrogel plots registered 12.97% higher economic returns over control. The results suggested that P-hydrogel (2.5 kg ha-1) reduces runoff water loss in full irrigation applied plots and retained more water, where loss of water is more thus reduces number of irrigations. Hence P-hydrogel with irrigation water is a viable option for sustainable production of soybean-wheat systems in the Indo-Gangetic plains of India and other similar eco-regions of the world.

Pesticidal seed coats based on azadirachtin-A: release kinetics, storage life and performance.

BACKGROUND: Infestation of seeds by pests during storage leads to deterioration in quality. Seed coating is an effective option to overcome the menace. Unlike synthetic fungicidal seed coats, little is known of those based on botanicals. This study aims at developing azadirachtin-A-based pesticidal seed coats to maintain seed quality during storage. RESULTS: Polymer- and clay-based coats containing azadirachtin-A were prepared and evaluated for quality maintenance of soybean seed during storage. Gum acacia, gum tragacanth, rosin, ethyl cellulose, hydroxyethyl cellulose, polyethyl methacrylate, methyl cellulose, polyethylene glycol, polyvinyl chloride, polyvinyl acetate, polyvinyl pyrrolidone and Agrimer VA 6 polymers and the clay bentonite were used as carriers. The time for 50% release (t(1/2)) of azadirachtin-A into water from the seeds coated with the different coats ranged from 8.02 to 21.36 h. The half-life (T(1/2)) of azadirachtin-A in the coats on seed ranged from 4.37 to 11.22 months, as compared with 3.45 months in azadirachtin-A WP, showing an increase by a factor of nearly 1.3-3.3 over the latter. The coats apparently acted as a barrier to moisture to reduce azadirachtin-A degradation and prevented proliferation of storage fungi. Polyethyl methacrylate, polyvinyl acetate and polyvinyl pyrrolidone were significantly superior to the other polymers. Azadirachtin-A showed a significant positive correlation with seed germination and vigour, and negative correlation with moisture content. CONCLUSION: Effective polymeric carriers for seed coats based on azadirachtin-A are reported. These checked seed deterioration during storage by acting as a barrier to moisture and reduced the degradation of azadirachtin-A.

Controlled release formulations of acephate: water and soil release kinetics.

Controlled release formulations of insecticide acephate (O,S-dimethyl acetylphosphoramidothioate) have been prepared using commercially available polyvinyl chloride, carboxy methyl cellulose and carboxy methyl cellulose with kaolinite. Kinetics of acephate release in soil and water from the different formulations was studied in comparison with the commercially available formulation 75 DF. Release from the commercial formulation was faster than the new controlled pesticide release (CR) formulations. Addition of clay in the carboxy methyl cellulose matrix reduced the rate of release. The diffusion exponent (n value) of acephate in water and soil ranged from 0.462 to 0.875 and 0.420 to 0.547 respectively in the tested formulations. The release was diffusion controlled with a half release time (T(1/2)) of 2.97 to 52.41 days in water and 2.98 to 76.38 days in soil from different matrices. The maximum release of acephate in water and soil from controlled released formulations occurred between 6.33 to 36.34 and 12.49 to 29.09 days respectively. The results suggest that depending upon the polymer matrix used, the application rate of acephate can be optimized to achieve insect control at the desired level and period.

Isolation and simultaneous LC analysis of thiram and its less toxic transformation product in DS formulation.

A simple and sensitive high pressure liquid chromatographic method has been developed for the simultaneous determination of Thiram and its transformation product using isocratic mixture of methanol-water (65:35) at flow rates of 0.75 mL min(-1), PDA detector using UV absorbance (lambda(max)) at 217 nm for Thiram and 265.5 nm for the transformation product. The transformation product was isolated from the commercial DS formulation and has been tentatively assigned the structure by (1)H NMR and ESI-MS spectral data. The separation is dependent on the nature of the mobile phase, its flow rate and the nature of the HPLC column. The detection limit (signal/noise; S/N = 3) for both Thiram and its transformation product was 0.2 ppm. The method has been successfully applied to analysis of soil and soybean samples spiked with Thiram, its transformation product and a commercial sample containing these products.

Field efficacy of azadirachtin-A, tetrahydroazadirachtin-A, NeemAzal and endosulfan against key pests of okra (Abelmoschus esculentus).

UNLABELLED: BACKGROUND Unlike synthetic pesticides, azadirachtin-based neem pesticides are environmentally friendly and are well known for their diverse pest control properties. Their use is, however, limited by the instability of azadirachtin, necessitating application at short intervals. The efficacy of relatively stable tetrahydroazadirachtin-A, therefore, needed to be established under field conditions. RESULTS: Azadirachtin-A (Aza-A), its stable derivative tetrahydroazadirachtin-A (THA) and other neem pesticides have been evaluated for their field efficacy against major insect pests of okra, Abelmoschus esculentus (L.) Moench., during summer (kharif) 2003 and 2004. The optimum doses of Aza-A and THA against the fruit borer, Earias vittella F., were also established. Reductions in population of whitefly, Bemisia tabaci (Genn.), and leafhopper (jassid), Amrasca biguttulla biguttulla Ishida, after application of THA or endosulfan was evident up to 10 days after treatment (DAT), whereas with Aza-A and NeemAzal (NZ) the effect was observed up to 7 DAT only. Endosulfan and THA also caused higher reduction in the larvae of shoot and fruit borer E. vittella and E. insulana Boisd., and recorded the highest yields of 4600 and 4180 kg ha(-1). The efficacy of THA (0.05 g L(-1) emulsion) was comparable with that of 0.5 g L(-1) endosulfan emulsion in reducing fruit borer infestation, the reduction over the control being 86.0 and 87.3%, 84.9 and 94.1% and 90.2 and 92.6% at first, second and third picking. THA 0.02 g L(-1) and Aza-A 0.05 g L(-1) were on a par. Laboratory-made neem oil emulsifiable concentrate was the least effective, but was superior to untreated check. CONCLUSION: Three consecutive sprays of THA, a neem-based biopesticide, and endosulfan have been found to be superior in controlling field pests of okra to Aza-A and NZ, which were on a par. THA thus holds potential as a component of pest management strategies against okra pests.

Development of controlled release formulations of carbofuran and evaluation of their efficacy against Meloidogyne incognita.

Controlled release (CR) formulations of the insecti-nematicide carbofuran have been prepared using commercially available rosin, sodium carboxymethylcellulose and sodium carboxymethylcellulose with clay (bentonite, kaolinite, and Fuller's earth). The kinetics of carbofuran release in soil from the different formulations were studied in comparison with that of the commercially available granules (3G). Release from the commercial formulation was faster than with the new CR formulations. Addition of clay in the biodegradable polymer matrix reduced the rate of release. The diffusion exponent (n value) of carbofuran in soil ranged from 0.462 to 0.740 in the tested formulations. The half-release (t1/2) values ranged between 4.79 and 25.11 days, and the period of optimum availability (POA) of carbofuran ranged from 15.10 to 43.97 days. The mean EC50 of the commercial formulation against Meloidogyne incognita was quite high as compared to those of CR formulations. The effective duration (te) of carbofuran from the CR and commercial formulations was predicted by fitting the mean EC50 values of test formulations in the model (M(infinity) - Me)/M(infinity) = Kdte. It was 0.7 day in commercial 3G in comparison with 17.8 days for CMC-bentonite. The bioassay studies revealed that with the rosin-yellow polymer, the dose of carbofuran could be reduced to half of its recommended dose for nematode control. Overall, a comparison of CR formulations with the commercial one showed an earlier degradation of carbofuran in the latter and relatively prolonged activity in the former.

Azadirachtin-A and tetrahydroazadirachtin-A concentrates: preparation, LC-MS characterization and insect antifeedant/IGR activity against Helicoverpa armigera (Hübner).

A 60% azadirachtin-A concentrate has been obtained through repeated precipitation with hexane from a methanolic solution of a 20% concentrate. Azadirachtin-A (90%) has been obtained by medium-pressure liquid chromatography of the 60% concentrate with an RP-18 column and a methanol + water (1 + 1 by volume) solvent system. Catalytic hydrogenation of the 60 and 90% azadirachtin concentrates yielded the corresponding tetrahydroazadirachtin concentrates. Dihydroazadirachtin and tetrahydroazadirachtin formed during the first 5 h of hydrogenation were identified by LC-ESI-MS on the basis of their unique mass fragmentation pattern. The efficacy of tetrahydroazadirachtin concentrates in inhibiting the feeding and growth of Helicoverpa armigera (Hübner) larvae has been compared with that of azadirachtin concentrates. They were in general more active and deterred larvae from feeding at all concentrations. Tetrahydroazadirachtin-A (90%) and azadirachtin-A (90%) with respective IC(50) values of 280 and 390 mg L(-1) were effective as insect growth regulators, while tetrahydroazadirachtin-A (90%) displayed higher antifeedant activity (AI(50) 14 mg L(-1)) against the test insect.

Liquid chromatographic method for the analysis of two plant based insecticide synergists dillapiole and dihydrodillapiole.

A reversed-phase LC method for the determination of two plant based insecticide synergists dillapiole (5-allyl 6,7-dimethoxy 1,3-benzodioxole) and dihydrodillapiole (5-n-propyl 6,7-dimethoxy-1,3-benzodioxole) is reported. The resolution of dillapiole and dihydrodillapiole has been achieved on RP-18 column using methanol-water (90:10, v/v) as mobile phase and a photodiode array detector at 207 nm. The response was linear in the range of 25-250 microg. The developed isocratic RP-LC method was validated for specificity, linearity, precision, and accuracy. It has been applied for individual or simultaneous detection, monitoring and quantification of dillapiole and dihydrodillapiole from treated French bean Phaseolus sp.

An efficient method for the purification and characterization of nematicidal azadirachtins A, B, and H, using MPLC and ESIMS.

Azadirachtin A enriched concentrate containing 60% active ingredient (a.i.) was prepared from the methanolic extract of the de-fatted neem (Azadirachta indica A. Juss) seed kernels. Azadirachtins A, B, and H, the three major bioactive constituents of neem seed kernel, were purified from this methanolic concentrate by employing reverse phase medium-pressure liquid chromatography (MPLC), using methanol-water solvent system as an eluant. The three pure azadirachtin congeners thus obtained were characterized by their unique mass spectral fragmentation, using electrospray probe in positive ion mode (ESI). All three azadirachtins exhibited nematicidal and antifungal activities. Azadirachtin B was the most effective against the reniform nematode Rotylenchulus reniformis (EC(50) 96.6 ppm), followed by Azadirachtin A (119.1 ppm) and H (141.2 ppm). At 200-ppm concentration, the test compounds caused 50-65% mortality of Caenorhabditis elegans nematode. Azadirachtin H showed the highest activity against the phytophagous fungi Rhizoctonia solani (EC(50) 63.7 ppm) and Sclerotium rolfsii (EC(50) 43.9 ppm), followed by B and A. The isolation of pure azadirachtins A, B, and H directly by MPLC purification from its concentrate and their characterization by ESIMS are unique and less time-consuming.

Activity of alkanediol alkanoates against pathogenic plant fungi Rhizoctonia solani and Sclerotium rolfsii.

Thirty known dialkanoates of ethylene, propylene and diethylene glycols were synthesized by reacting the glycols with acyl chlorides and their structures confirmed by IR, NMR and mass spectral analyses. They exhibited significant antifungal activity against two phytopathogenic fungi Rhizoctonia solani Kuehn and Sclerotium rolfsii Sacc in a dose dependent manner. Propylene glycol dipentanoate was the most active against R. solani. followed by diethylene glycol dibutanoate and ethylene glycol dibutanoate. Against S. rolfsii ethylene glycol diheptanoate was found to be most active followed by diethylene glycol diisobutanoate As compared to the standard reference benomyl (EC50 5.16 microg/mL), the potential alkanediol dialkanoates showed EC50 in the range of 33 - 60 microg/mL.

Structure-biological activity relationships in triterpenic saponins: the relative activity of protobassic acid and its derivatives against plant pathogenic fungi.

BACKGROUND: Triterpenic saponins from Sapindus mukorossi Gaertn. and Diploknema butyracea JF Gmelin were evaluated for in vitro antifungal activity against four phytopathogenic fungi. The study of the structure-antifungal activity relationships of protobassic acid saponins was widened by including semi-synthetic derivatives. RESULTS: Diploknema butyracea saponins exhibited significant antifungal activity against three fungi (ED(50) 230-455 microg mL(-1)), whereas S. mukorossi saponin was effective against two fungi (ED(50) 181-407 microg mL(-1)). The n-butanol extract after preparative HPLC separation provided two saponins from D. butyracea saponin mixture: 3-O-[beta-D-glucopyarnosyl-beta-D-glucopyranosyl]-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-glucopyranosyl-xylopyranosyl]-arabinopyranoside (MI-I), and 3-O-beta-D-glucopyranosyl-glucopyranosyl-glucopyranosyl-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-xylopyranosyl-arabinopyranosyl]-apiofuranoside (MI-III). The single saponin extracted from S. mukorossi saponin mixture was identified as 3-O-[O-acetyl-beta-D-xylopyranosyl-beta-D-arabinopyranosyl-beta-D-rhamnopyranosyl] hederagenin-28-O[beta-D-glucopyranosyl-beta-D-glucopyranosyl-beta-D-rhamnopyranosyl] ester (SM-I). Monodesmosides resulting from the partial degradation of hederagenin and hydroxyprotobassic acid bisdesmosides exhibited significant reduction in antifungal effect. Further removal of sugar moiety yielded complete loss in activity. The antifungal activity of the triterpenic saponins was associated with their aglycone moieties, and esterification of the hydroxyl group led to change in antifungal activity. CONCLUSION: Sapindus mukorossi saponin, which is effective against Rhizoctonia bataticola (Taub.) Briton Jones and Sclerotium rolfsii Sacc., can be exploited for the development of a natural fungicide. A sugar moiety is a prerequisite for the antifungal activity of triterpenic saponin.

Screening for feeding deterrent and insect growth regulatory activity of triterpenic saponins from Diploknema butyracea and Sapindus mukorossi.

Antifeeding and insect growth regulatory effects of saponins and its hydrolyzed products from Diploknema butyracea and Sapindus mukorossi on the insect pest Spodoptera litura (F.) were investigated in the laboratory. D. butyracea saponins as well as their hydrolyzed prosapogenins were found to be better biologically active in controlling pests. A concentration of 1200 and 3400 mg L(-1) alkaline and acid hydrolyzed D. butyracea saponins exhibited significant antifeeding and toxic effects to third instar larvae when compared to the emulsified water as control. The n-BuOH extract after prep-HPLC separation provided two saponins from the D. butyracea saponin mixture: 3-O-[beta-D-glucopyarnosyl-beta-d-glucopyranosyl]-16-alpha-hydroxyprotobassic acid-28-O-[ara-glc-xyl]-ara (MI-I) and 3-O-beta-D-glucopyranosyl-glucopyranosyl-glucopyranosyl-16-alpha-hydroxyprotobassic acid-28-O-[ara-xyl-ara]-apiose (MI-III). The single saponin extracted from the S. mukorossi saponin mixture was 3-O-[beta-D-xyl(OAc).beta-D-arabinopyranosyl.beta-D-rhamnopyranosyl] hederagenin-28-O-[beta-D-glc.beta-D-glc.beta-D-rhamnopyranosyl] ester (SM-I). Five days after saponin treatment on larvae, the growth index (GI50) was reduced from 0.92% to 1520 ppm in alkaline hydrolyzed D. butyracea saponins. Upon hydrolysis, growth regulatory activity was improved in S. mukorossi saponin, whereas very little difference was found in antifeedant activity. Hydrophile-lipophile balance is important for the proper functioning of saponin/prosapogenin/sapogenin, which could be achieved by manipulating the sugar molecule in the triterpenic skeleton.