Insect-Mediated Dispersal of the Rhizobacterium Pseudomonas chlororaphis

ABSTRACT The southern corn rootworm, Diabrotica undecimpunctata subsp. howardi, a common and mobile insect pest, was shown to transmit the rhizobacte-rium Pseudomonas chlororaphis strain L11 between corn plants. Strain L11 has been genetically modified to contain the lacZY genes from Escherichia coli. It can reach high densities on roots and invade the roots and move into the foliage. D. undecimpunctata subsp. howardi became infested with L11 as larvae while feeding on roots of seed-inoculated corn and retained the bacteria through pupation, molting to the adult stage, and emergence from the soil. Bacterial densities on or in the insects increased 100-fold after they fed again as adults on L11-infested foliage. Adults retained the bacteria for at least 2 weeks after last exposure and could transmit L11 to new plants. The likelihood of transmission decreased with time since last exposure to L11, but increased with time spent on the new plants. This research demonstrates that rhizobacteria can escape the rhizosphere by moving in or onto foliage, where they can then be acquired and transmitted by insects. This transmission route may be common among naturally occurring rhizobacteria and facilitate the dispersal of both beneficial and harmful soilborne microorganisms.     

Interaction of Fusarium graminearum and F. moniliforme in Maize Ears: Disease Progress, Fungal Biomass, and Mycotoxin Accumulation

ABSTRACT To investigate the interaction between two major ear-rotting pathogens, maize ears were inoculated with either Fusarium graminearum, F. moniliforme, or an equal mixture of the two. Silk and kernel tissues were periodically harvested throughout the growing season so that a time course of the experimental variables (disease severity, ergosterol content, fungal DNA content, and mycotoxin concentration) could be recorded. Over the 3 years tested (1992 to 1994), the highest levels of disease and ergosterol were found in the F. graminearum treatment, followed by the mixture treatment (F. graminearum plus F. moniliforme) and, finally, the F. moniliforme treatment. Kernel ergosterol content and disease rating were correlated for both pathogens, but the highest correlation coefficients were obtained in the F. graminearum treatment. The DNA analysis revealed that, in the mixed inoculum, F. moniliforme had a greater growth rate than did F. graminearum. In 1994, appreciable F. moniliforme from natural inoculum was found in the F. graminearum treatment. Fumonisin B(1) levels did not differ between the F. moniliforme treatment and the mixed inoculum treatment. The effect of temperature on the growth rate of the two species explained some of the field results, with temperatures in the silks being more favorable to F. moniliforme. Data on the growth rate on silks obtained by the incorporation of radiolabeled precursor to ergosterol demonstrated that F. graminearum was able to grow well at 26 to 28 degrees C, whereas F. moniliforme grew well over a broader range, including at higher temperatures.     

Effects of dietary cysteine on blood sulfur amino acid, glutathione, and malondialdehyde concentrations in cats

OBJECTIVE: To determine effects of dietary cysteine on blood sulfur amino acids (SAA), reduced glutathione (GSH), oxidized glutathione (GSSG), and malondialdehyde (MDA) concentrations in cats. ANIMALS: 12 healthy adult cats. PROCEDURE: Cats were fed diets with a nominal (0.50 g/100 g dry matter [DM]), moderate (1.00 g/100 g DM), or high (1.50 g/100 g DM) cysteine content in a 3 X 3 Latin square design with blocks of 8 weeks' duration. Venous blood samples were collected after each diet had been fed for 4 and 8 weeks, and a CBC and serum biochemical analyses were performed; poikilocyte, reticulocyte, and Heinz body counts were determined; and MDA, GSH, GSSG, and SAA concentrations were measured. RESULTS: Blood cysteine and MDA concentrations were not significantly affected by dietary cysteine content. Blood methionine, homocysteine, and GSSG concentrations were significantly increased when cats consumed the high cysteine content diet but not when they consumed the moderate cysteine content diet, compared with concentrations obtained when cats consumed the nominal cysteine content diet. Blood GSH concentrations were significantly increased when cats consumed the moderate or high cysteine content diet. CONCLUSIONS: Increased dietary cysteine content promotes higher blood methionine, homocysteine, GSH, and GSSG concentrations in healthy cats. CLINICAL RELEVANCE: Supplemental dietary cysteine may be indicated to promote glutathione synthesis and ameliorate adverse effects of oxidative damage induced by disease or drugs.     

Responses of carbon gain and growth of Pinus radiata stands to thinning and fertilizing

Thinning of forest stands is widely carried out to minimize the slowing of growth of individual stems that follows from increasing competition among trees as they become bigger. After thinning, there is an increase in the growth rate of remaining trees because of an increase in the availability of resources per tree. Often, there is also an increase in foliar efficiency (biomass increase/foliage amount). On sites where mineral nutrient supply is limiting, fertilizers may be applied, often in association with thinning, to boost productivity. Growth responses to fertilizer application depend on an adequate supply of other resources, but also involve nonlinear interactions among mineral nutrients and between nutrients and other growth-limiting environmental factors. The effects of thinning and fertilizing on the carbon gain and growth responses of Pinus radiata D. Don to availability of resources (light, mineral nutrients and water) and to changes in the canopy are discussed.     

使用电孵机的经验教训

营销是企业成功的关键因素，“营销”一词不应该被认为是过去大家认定的销售，而必须赋予新的意义——满足顾客需要（菲力普·科特勃）。俗话说：“顾客是我们的衣食父母”，企业依存于顾客。无数企业的兴衷无不印证这一道理：只有将企业的经营目标与顾客的需求和期望有机地结合起来，企业才能生存和发展；只有重视顾客的利益，为顾客创造价值，企业才会有旺盛的生命力。目前，顾客满意已成为所有优秀企业追求的重要经营目标之一，而顾客满意度比利润更能体现企业经营业绩的好坏。顾客满意度不仅可以体现企业当前的经营状况，而且可以更深刻地揭示企业经营中存在的一些深层次的问题，如企业的质量文化、经营理念等等。