Patterns of cover crop use,adoption, and impacts among Indiana farmers

Cover crops have recently been generating a lot of interest in agriculture for their agronomic benefits, including erosion control, nutrient restoration, and increased cash crop yield. However, the value of these benefits is not well established and likely highly variable. The factors that influence a farmer’s decision to adopt or not adopt cover crops are also a point of interest to conservationists and policy makers. As part of a long-term study estimating the benefits and costs of cover crops, this study analyzed five years of historic information collected from Indiana farmers, who either grew or did not grow cover crops. No significant impact was found from cover crops on cash crop yields, but several interesting correlations in cover crop use were found. Cover crop use was higher on steeper fields. There was also a high correlation between the use of cover crops and no-till.     

美国印第安纳州玉米种质资源的利用研究

根据不同特点选取铁97005、铁98012、铁98033、铁98042、铁98103、铁98127等共6份自交系作为试验材料,分别以分属不同杂种优势群的自交系吉853、丹340、Mo17和沈137作为标准测验种,按Griffing完全双列杂交法Ⅳ组配出45个杂交组合,通过对杂交组合间的杂种优势和配合力的分析与比较。结果表明,利用美国印第安纳州种质资源选育的二环系与旅大红骨类群自交系、唐四平头类群自交系、PN类群自交系在单株产量性状上均具有较大的配合力,其中自交系铁98012、铁98033、铁98103的利用价值较高。     

美国印第安纳玉米种质资源引进及资源分析

通过对1997～1998年从美国印第安纳州种子批发公司引进的玉米种质资源进行分析、鉴定等，探讨其在我国玉米生产上的应用价值。引进杂文种熟期较早，株高适中，可以通过增加株数来提高产量。引进自交系与我国目前骨干自交系测配结果：与旅大红管改良系具有较强的配合力；与唐四平头改良系也具有一定的配合力；与Ried黄马牙系统配合力表现一般；与合热带么缘系统改良系具有较强的配合力。通过1997～1998年对引进杂文种试验，对自文系观察、鉴定，自文系DM2在丰产性与配合力方面表现良好，但DM2在抗性方面表现较差，多数自交系可通过改良加以利用。     

Evaluation of the enzyme-amplified ELISA for the detection of potato viruses A,M, S,X, Y,and leafroll

Various parameters,e.g. types of microtiter plate for DAS-ELISA (double antibody sandwich-enzyme-linked immunosorbent assay), use of fresh or frozen amplifier solutions for enzyme-amplified-ELISA, and use of sodium diethyldithiocarbamate (NaDIECA) in sample buffer in cocktail-ELISA were evaluated for the detection of potato viruses A, M, S, X, Y and leafroll from potato foliage. Dynatech Immulon immunoplates provided higher readings for all viruses. Fresh amplifier solution in amplifed-ELISA was superior to frozen solutions. Amplified ELISA gave only marginal improvement in the sensitivity over the standard DAS-ELISA. Addition of NaDIECA in sample buffer did not improve the detection of viruses in DAS-, amplified-, or cocktail-ELISA. Cocktail-ELISA can reduce antigen incubation time to as short as 15 min for PVA, PVM and PVX; 1 hr for PVY and PLRV; and 2–4 hr for PVS using pre-coated plates. Although amplified-ELISA is slightly more sensitive than DAS-ELISA for certain potato viruses, it is not suitable for large-scale indexing of potato viruses in Seed Certification Laboratories, in view of the additional steps needed in carrying out this procedure.     

On the Chemistry,Toxicology and Genetics of the Cyanobacterial Toxins,Microcystin, Nodularin,Saxitoxin and Cylindrospermopsin

The cyanobacteria or “blue-green algae”, as they are commonly termed, comprise a diverse group of oxygenic photosynthetic bacteria that inhabit a wide range of aquatic and terrestrial environments, and display incredible morphological diversity. Many aquatic, bloom-forming species of cyanobacteria are capable of producing biologically active secondary metabolites, which are highly toxic to humans and other animals. From a toxicological viewpoint, the cyanotoxins span four major classes: the neurotoxins, hepatotoxins, cytotoxins, and dermatoxins (irritant toxins). However, structurally they are quite diverse. Over the past decade, the biosynthesis pathways of the four major cyanotoxins: microcystin, nodularin, saxitoxin and cylindrospermopsin, have been genetically and biochemically elucidated. This review provides an overview of these biosynthesis pathways and additionally summarizes the chemistry and toxicology of these remarkable secondary metabolites.     

Exposure to the Neurotoxic Dinoflagellate,Alexandrium catenella,Induces Apoptosis of the Hemocytes of the Oyster,Crassostrea gigas

This study assessed the apoptotic process occurring in the hemocytes of the Pacific oyster, Crassostrea gigas, exposed to Alexandrium catenella, a paralytic shellfish toxins (PSTs) producer. Oysters were experimentally exposed during 48 h to the toxic algae. PSTs accumulation, the expression of 12 key apoptotic-related genes, as well as the variation of the number of hemocytes in apoptosis was measured at time intervals during the experiment. Results show a significant increase of the number of hemocytes in apoptosis after 29 h of exposure. Two pro-apoptotic genes (Bax and Bax-like) implicated in the mitochondrial pathway were significantly upregulated at 21 h followed by the overexpression of two caspase executor genes (caspase-3 and caspase-7) at 29 h, suggesting that the intrinsic pathway was activated. No modulation of the expression of genes implicated in the cell signaling Fas-Associated protein with Death Domain (FADD) and initiation-phase (caspase-2) was observed, suggesting that only the extrinsic pathway was not activated. Moreover, the clear time-dependent upregulation of five (Bcl2, BI-1, IAP1, IAP7B and Hsp70) inhibitors of apoptosis-related genes associated with the return to the initial number of hemocytes in apoptosis at 48 h of exposure suggests the involvement of strong regulatory mechanisms of apoptosis occurring in the hemocytes of the Pacific oyster.