Effect of biocontrol agents and biofertilizers on root rot,yield, harvest index and nutrient uptake of cassava (Manihot esculanta Crantz)

Cassava is an important subsidiary food and industrial raw material in the tropics. Root rot disease, caused by Phytophthora palmivora, poses a serious threat to cassava cultivation in Tamil Nadu, India. Field experiments (2008–09) were conducted to study the effect of biocontrol agents (Trichoderma spp. and Pseudomonas fluorescens) and biofertilizers (Azospirillum, vesicular–arbuscular mycorrhizal fungi and phosphorus-solubilizing bacteria) on root rot, yield, harvest index and nutrient uptake of cassava at two NPK rates. The design of the experiment was a split plot with two NPK rates, recommended and 50% recommended rate, as the main plot treatments and five biocontrol agents and biofertilizers as subplot treatments. The results clearly indicated that use of a bioinoculants consortium significantly reduced root rot infection/disease incidence over uninoculated controls. Azospirillum significantly improved the yield of cassava at 50% of the recommended rate of NPK. NPK rates had no significant impact on harvest index of cassava and Trichoderma and vesicular–arbuscular mycorrhizal fungi resulted in a higher harvest index even at 50% of the recommended NPK rate. Nitrogen, phosphorus and potassium uptake was significantly improved when treated with biofertilizers and/or a consortium.     

Flowing solution culture system maintains uniform root environment composition

Flowing solution culture enables the researcher to study effects of root environment variables independently. This flowing solution culture system utilizes air pressure and syphoning or a peristaltic pump to circulate the nutrient solution. Because this system is inexpensive, simple in design, and compact, several factors can be studied concurrently, treatments can be replicated to test for system effects, nutrient deviations, and block for growth effects due to environment. These systems have been used successfully with experiments in N form, plant growth regulators, salt stress, and mechanical stress. Non‐destructive measurements of root growth and nutrient uptake are possible.     

The physical stability of suspension concentrates with particular reference to pharmaceutical and pesticide formulations

The word stability is ubiquitous in colloid science but means different things to different people. In a suspension concentrate it is possible to identify three different physical processes which may lead to instability in a particulate system, namely a change in particle size due to Ostwald ripening, particle aggregation and particle sedimentation. Although these processes may occur simultaneously they are here treated separately in order to promote understanding of the physical forces involved.     

Distribution and metabolism of abamectin in larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae)

Comparisons were made between the amounts of abamectin and total radioactivity recovered from Spodoptera littoralis and Heliothis armigera larvae after topical application of [³H]abamectin. Penetration (as shown by wash-off experiments) did not differ significantly between the Spodoptera instars. Significantly more abamectin was recovered from ventral nerve cord samples of larvae showing symptoms of poisoning than from larvae not showing these symptoms. Fifth-instar S. littoralis larvae had a significantly lower proportion of radioactivity as abamectin in the ventral nerve cord than in sixth-instar S. littoralis or fifth- and sixth-instar H. armigera. The proportion of radioactivity present as abamectin (but not total radioactivity) was significantly increased when the fifth-instar S. littoralis larvae were pre-treated with piperonyl butoxide (PB) suggesting that the relative insensitivity of fifth-instar S. littoralis larvae to abamectin is due at least in part to greater metabolism, particularly by microsomal oxidases. Fat body samples consistently had a greater proportion of radioactivity as abamectin than the nerve cord and the former may act as storage sites for abamectin.     

Interactions of insecticides with biological membranes

Many insecticides (e.g. DDT, lindane, pyrethroids) are hydrophobic molecules which bind extensively to biological membranes. Binding of insecticides to phospholipid bilayers frequently shows saturation, with binding increasing with increasing insecticide concentration up to some limit, beyond which no further insecticide is incorporated into the bilayer. For lindane, this limit has been shown to correspond to the concentration at which the aqueous phase becomes saturated. Simple alkanes show similar saturation phenomena, and binding of halogenated alkanes can be followed by fluorescence quenching methods. It is shown that effects of hydrophobic molecules on bilayer fluidity are small. Effects of alkanes and insecticides on the activity of the (Ca²⁺-Mg²⁺)-ATPase purified from sarcoplasmic reticulum follow from direct binding to the ATPase, at sites which are not at the lipid-protein interface of the ATPase.     

Studies on pesticides based on coumarin. II. Synthesis and antifungal activity of ten 2-alkyl-7, 8-dihydro-3-hydroxynaphtho[1,2-c]chromen-6-ones

A series of 2-alkyl-7, 8-dihydro-3-hydroxynaphtho[1,2-c]chromen-6-ones was synthesised by the condensation of ethyl 3, 4-dihydro-1-oxonaphthalene-2-carboxylate with substituted phenols in the presence of POCl₃. The compounds were characterised and tested for their toxicity towards the mycelial growth of seven phytopathogenic fungi in culture. Drechslera oryzae, Rhizoctonia solani and Colletotrichum falcatum exhibited maximum sensitivity to these compounds whereas Macro-phomina phaseolina, Fusarium solani, Alternaria alternata and Pythium aphanidermatum were less sensitive. 2-Ethyl-7, 8-dihydro-3-hydroxy-naphtho[1,2-c]chromen-6-ones possessed greatest toxicity with EC₅₀ values ranging from 0.2 to 2.5 μg ml^?1 against all fungi except A. alternata and P. aphanidermatum.     

The physical and chemical properties of the herbicide cinmethylin (SD 95481)

Cinmethylin (SD 95481), is a novel herbicide developed for the selective pre-emergence control of many annual grass weeds in a wide range of temperate and tropical crops. Representing new herbicide chemistry, cinmethylin is in the cineole family. Cinmethylin is a mobile colourless liquid with a boiling point of 313°C under an inert atmosphere at atmospheric pressure. It has a density of 1015 kg m^?3 and a viscosity of 70–90 mPa s, both at 20°C. It is miscible in all proportions with most organic solvents but has a low solubility, 63 mg litre^?1, in water. It has a vapour pressure of 10.2 mPa (20°C) and the vapour pressure/temperature relationship is given by log_e P(Pa)=28.9–9816/T (K). The n-octanol/water partition coefficient is 6850 and soil organic matter/water sorption coefficient (K_om) ranges between 165 and 235 over the three types of soil used in these studies. Cinmethylin is stable in water over the pH range 3–11. Solutions of cinmethylin in water or solvents are reasonably stable to sunlight, though thin films on a quartz surface photooxidise mainly to an ester within 24 h. This rate can be reduced by the addition of photostabilisers or by sorption onto soil surfaces. In an inert atmosphere cinmethylin is stable to high temperatures, though, in air, oxidation occurs at temperatures above 100°C to give the same product as by photodecay.     

Physiological interactions between the herbicide EPTC and selected analogues of the antidote naphthalic anhydride on two hybrids of maize

The efficacies of nine structural analogues of the herbicide antidote naphthalene-1,8-dicarboxylic acid anhydride (naphthalic anhydride, NA) for the protection of maize (Zea mays L. cv. DeKalb XL72AA and DeKalb XL67) against injury by the herbicide S-ethyl dipropyl(thiocarbamate) (EPTC) were elevated under greenhouse conditions. The chemical analogues of NA tested were: acenaphthenequinone (ACQ); 4-aminonaphthalene-1,8-dicarboxylic acid anhydride (NH₂NA); 1,8:4,5-naphthalenetetracarboxylic acid dianhydride (NDiA); naphthalene- 1,8-carboximide (NHNA); 4-chloronaphthalene-1,8-dicarboxylic acid anhydride (C1NA); biphenyl-2,2′-dicarboxylic acid anhydride (diphenic anhydride; DA); 2-phenylglutaric anhydride (PGA); phthalic anhydride (PHA); phenalen-1-one (PA). Pre-plant incorporated applications of EPTC at 2.2, 4.5, 6.7, and 9.0 kg ha^?1 were highly toxic to XL67 maize. Appreciable injury to XL72AA maize by EPTC was observed only with the high rates of EPTC (6.7 and 9.0 kg ha^?1). Of the analogues tested PGA and PA were very toxic and inhibited germination of both maize hybrids. NA, ACQ, NH₂NA, NDiA, NHNA, C1NA, DA, and PHA applied as seed dressings at 5.0 and 10 g per kg of seed offered satisfactory protection to XL72AA maize against EPTC rates higher than 6.7 kg ha^?1. The same antidotes significantly antagonised the EPTC activity against XL67 maize but the overall protection obtained was partial and not agronomically important. The presence of the dicarboxylic anhydride group and of at least one aromatic ring attached directly to the anhydride appeared to be essential for the exhibition of protective activity by the structural analogues of NA. NA was slightly toxic to both hybrids of maize and chlorination of NA increased the phytotoxicity of this molecule. A genetic component that is present in the thiocarbamate-tolerant XL72AA hybrid but absent from the thiocarbamate-susceptible XL67 hybrid of maize appeared to be important for the phytotoxic activity of EPTC and may be involved in the protective activity of NA and its structural analogues.     

New mite-borne virus isolates from rakkyo,shallot and wild leek species

Flexuous viruses were transmitted from rakkyo (Allium chinense) and wild leek species (especiallyA. commutatum) to plants of crow garlic (A. vineale), by transfer of dry bulb mites. By electron microscope decoration tests using three antisera and by inoculations onto test plants, it was concluded that from each of the two natural host species at least two viruses were isolated. The viruses from wild leeks are both pathogenic onAllium spp. and may be of economic importance. Decoration tests on a virus mixture from shallot obtained earlier, revealed another new mite-borne virus in this species. The mite-borne viruses ofAllium spp. appear to be very common; they are largely diverse and their identification remains difficult.     

Exploration of glycoprotein structures: Sequences and consequences

The vast expansion in our knowledge of the detailed molecular structure of many glycoproteins has been achieved by purpose-designed methodologies. In this review, principal experimental methods for gaining fundamental evidence are assessed with respect to well-known iV-glycoproteins (e.g. ribonucleases), 0,N-glycoproteins (e.g. glycophorin A) and O-glycoproteins (e.g. submaxiilary gland mucins and some sulfated forms). Relevant properties of N-carbohydrate-peptide links (N-acetylglucosaminyl-asparagine) and O-linkages (N-acetylgalac-tosaminyl-Thr (or -Ser)) are reviewed and the classification and structure of more elaborate glycoproteins is outlined. Key reactions, both chemical and enzymic, effect the cleavage of N- and O-oligosaccharide side-chains from core protein, and subsequent calibrated chromatographic analysis can permit the identification of certain oligosaccharide groupings characteristic of glycoforms (families of glycoproteins different only in the oligosaccharide chain lengths and bond structures). Basic sequencing of individual oligosaccharides is generally achieved by chemical methods (e.g. methylation analysis, degradation with periodate) and by the action of well-characterised specific exo- and endoglycosidases. Degradation of a glycoprotein chemically (e.g. by cyanogen bromide) or enzymically by endopeptidases to glycopeptides provides means for locating oligosaccharide position(s) on the core protein. The presence of O-sulfate ester groups on oligosaccharide side-chains presents further challenging problems for sequencing investigations. Some correlations between oligosaccharide sequences and biological function are considered. While, in the main, the best-known glycoprotein structures are for those of mammalian origin (e.g. Igs), evidence points to other areas of interest in plants (especially yeasts), invertebrates and micro-organisms. Allusion is made to current comparative and fundamental physico-chemical techniques, especially gel permeation chromatography, membrane-transfer, FAB-MS and NMR (NOE, COSY, etc.).