Comparison of fungicides for the control of Rhizoctonia solani causing datnping-off of mung bean (Phaseohis aureus)

Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC₅₀ values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC₅₀ of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.     

Radiation-induced Organogenesis and Isoenzyme Patterns in Long-term Callus Cultures of Datura innoxia

Effect of gamma irradiation on growth, shoot organogenesis andenzyme activities and isoenzyme patterns of -amylase and peroxidaseduring differentiation in long-term calluses of Datura innoxiahave been investigated. Radiation in doses of 0.2 and 1.0 kRstimulated the shoot regeneration frequency as well as the numberof shoots per regenerating callus. The 0.2 kR dose could induceshoot organogenesis even in calluses incubated in the dark oncallusing medium, although with less frequency. Such cultures,however, showed profuse shoot regeneration when sub-culturedonto regeneration medium under light conditions. A higher radiationdose (5.0 kR) was lethal to both growth and shoot differentiation.Prior to shoot regeneration, -amylase and peroxidase specificactivities increased to four- to fivefold and 7–24-fold,respectively. While the amylase isoenzyme pattern remained unchanged,specific changes in the isoperoxidase pattern were observedduring shoot differentiation in callus cultures. The most significantchange was the appearance of fast-moving anodic bands priorto visible shoot differentiation. Thus, such isoperoxidasesprovide useful biochemical markers for shoot differentiation. Datura innoxia, shoot organogenesis, isoenzyme pattern, gamma-radiation, growth regulators     

Fungicidal control of Rhizoctonia solani in soil amended with organic manures

Amendments of nutrient-deficient soil with three organic manures and one non-edible oil-cake reduced the disease controlling potential of methoxyethyl mercury chloride (MEMC), quintozene and carbendazim used as seed treatments on cowpea and cotton against seedling rot caused by Rhizoctonia solani. Biogas sludge (BGS) and farm yard manure (FYM) nullified the activity of MEMC and quintozene and reduced markedly the efficacy of carbendazim. Humic acid extracted from BGS inactivated MEMC and carbendazim but had little effect on quintozene. Green manure (Sesbania aculeata) slightly reduced the efficacy of MEMC only. Soil amendment with mahua (Madhuca indica) cake and soil drench with its aqueous extract greatly reduced the efficacy of the three fungicides.     

Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels

Upper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha^-1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.^-1) increased significantly due to soil N application (N₃₀ over N₀). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)^-1 revealed that two-thirds of N is translocated by 28-day stage and the rest between 28-day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)^-1 at N₀, N₃₀ and N₁₂₀- respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.     

The Occurrence of Biogenic Calcian Struvite, (Mg, Ca)NH4PO4.6H2O, as Intracellular Crystals in Paramecium

ABSTRACT. Intracellular crystals are conspicuous refractile "inclusion bodies" commonly found in many protozoans, but very few have been identified mineralogically. We have isolated crystals from axenically grown mass cultures of Paramecium tetraurelia , and purified them using differential centrifugation. The crystals' structure and chemistry were analyzed using x-ray powder diffraction and energy-dispersive electron microprobe techniques. The morphology was studied by means of scanning electron microscopy. The crystals were identified as the orthorhombic mineral, calcian struvite, (Mg, Ca)NH₄PO₄.6H₂O. Struvite from P. tetraurelia exhibited a variety of crystal habits, including hemimorphic forms, epitactic overgrowths and several types of twins. A linear correlation between computed hydration number and Mg content suggests that the crystal composition may reflect the range of conditions under which struvite nucleation and growth occur. The mineral struvite also occurs in association with guano and other rich organic products, and can be biologically induced to precipitate extracellularly. Extracellular struvite has been well characterized in pathogenic calculi (kidney stones) of humans and cats, where precipitation is enhanced by bacterial urease activity that produces ammonia in the urinary tract. This is the first study demonstrating that struvite is also biologically controlled to form as an intracellular mineral. These crystals may have formed within lipid-rich, membrane-bound vesicles in Paramecium .     

Element Stoichiometry of a Mixotrophic Protist Grown Under Varying Resource Conditions

ABSTRACT. The balance of essential elements (e.g. carbon [C], nitrogen [N], and phosphorus [P]) between consumers and their resources influences not only the growth and reproduction of the consumers but also the nutrients they regenerate. Flagellate protists are significant predators of aquatic bacteria and directly influence nutrient flow to higher trophic levels and, through excretion, influence the mineral element composition of dissolved nutrients. Because the element stoichiometry of protists is poorly characterized, we varied the resource composition of the bacterium Pseudomonas fluorescens and used it to grow the mixotrophic bacterivorous flagellate Ochromonas danica. Using a mass balance approach, the element composition of O. danica was found to vary depending upon the nutrient composition of the prey and ranged between 482:36:1 and 80:12:1 (C:N:P molar). Homeostasis plots suggested that flagellate protists weakly regulate their element composition and are likely to regenerate different elements depending upon the nature of the element limiting growth of their prey.     

Effect of Aldrin on Growth and Oxidative Metabolism of Rhizobia

At 500 μg ml⁻¹ of aldrin, Rhizobium sp. Bengal gram ( Cicer arietinum ) and Rhizobium sp. Green gram (Vigna radiata ) showed a lag of about 12 h after which the growth returned to normal. The lag period was extended at concentrations above 500 μg ml⁻¹ of aldrin and it was more in the case of Rhizobium sp. Green gram than Rhizobium sp. Bengal gram. However, at high concentrations of aldrin, after the lag, the growth rate was very slow. On the seventh day, Rhizobium sp. Bengal gram showed 72, 81 and 84° inhibition while Rhizobium sp. Green gram exhibited 74, 85 and 88° inhibition of growth at 1000, 1500 and 2000 μg ml⁻¹ of aldrin, respectively. In general, oxidative activity of both of the Rhizobium spp. on pentoses, hexoses and TCA cycle intermediates was more strongly inhibited in aldrin grown cells than normal cells. The inhibitory effect of aldrin on the oxidative activity of rhizobia was partially released with a high concentration of glucose.     

A selective medium for isolating Rhizoctonia solani from soil

Ko & Hora's (1971) selective medium (FM) for counting Rhizoctonia solani propagules from soil has been modified. FM medium minus gallic acid and fenaminosulf i.e. mineral antibiotic (MA) medium, was amended with inhibitors and fungicides at different concentrations. The modified medium consisting of MA + gallic acid (400 μg ml^-1) + fosetyl-Al (250μgml^-1) was found most efficient in selective isolation of R. solani from soil even in the presence of Macrophomina phaseolina (Rhizoctonia bataticold) and other soil mycoflora. This amended medium was effective in isolating R. solani from soil even when the number of propagules of M. phaseolina present was 10 times greater. The sensitivity of this medium was five times better than Ko & Hora's medium.     

Control of pearl millet downy mildew caused by Sclerospora graminicola with systemic fungicides in an artificially-contaminated plot

Among four fungicides, viz. metalaxyl (two formulations), fosetyl-Al, pro-pamocarb and cyomaxanil tested in vitro against sporangial germination inhibition of Sclerospora graminicola, cyomaxanil was found to be most inhibitory. In an artificially contaminated plot, when used as seed treatment or foliar spray for the control of downy mildew of pearl millet, only metalaxyl was effective. Metalaxyl 25 (Ridomil) and metalaxyl 35 (Apron) seed treatments protected the pearl millet plants from downy mildew up to 30 days. As a foliar spray, metalaxyl 25 used once at 20 days or twice after 20 and 38 days of plant growth gave less disease at harvest time. Seed treatment (metalaxyl 25 or 35) followed by one metalaxyl 25 spray was found to be effective in controlling the downy mildew. These treatments improved the growth of plants and yield significantly.     

Dissolved Organic Matter as a Potential Source of Nutrition for Marine Organisms

The general features of accumulation of amino acids by marineinvertebrates are outlined. The wide distribution of this abilityis noted. Data from observations of this process for periodsof several days are presented for the polychaete worm, Doruilleaarticulata. Measurements of the constituents in the pool offree amino acids of this same organism are presented togetherwith data concerning the rate of appearance of radioactivityin the medium after permitting animals to accumulate amino acids.These data permit tentative estimates of rates at which aminoacids are lost to the medium. These apparent "leakage" ratesare low when compared with rates of uptake. The thermodynamicwork necessary to move material against the concentration differencesinvolved is calculated. The fraction of metabolic energy neededis small. The possible biological significance of uptake ofsmall organic compounds is discussed. It is concluded that uptakeof amino acids occurs sufficiently generally and at such ratesthat it should be included in any analysis of the pathways wherebymaterial is acquired from the environment by marine organisms.