Virulence characteristics of a new race of the parasitic angiosperm,Striga gesnerioides,from southern Benin on cowpea (Vigna unguiculata)

An in vitro growth system was used to determine the virulence of two samples of Striga gesnerioides from Zakpota in southern Benin. Cowpea variety B301, previously considered resistant to all races of S. gesnerioides, was susceptible to both samples of the parasite. Two other cowpea varieties, 58–57 and IT81D-994, were totally resistant. Resistance in 58–57 was associated with a hypersensitive necrosis of infected roots, whilst IT81D-994 supported production of small S. gesnerioides tubercles with stems which failed to develop. Striga gesnerioides from southern Benin is the fourth race of the parasite to be identified, and the first with virulence on variety B301. The implications for breeding cowpeas with resistance to S. gesnerioides are discussed.Abbreviations IITA International Institute of Tropical Agriculture - LARS Long Ashton Research Station - SAFGRAD Semi-Arid Food Grain Research and Development     

Effect of silver from cloud seeding on rumen microbial function

Hazards of Ag from weather modification to micro-organisms of the rumen were evaluated in vitro and in vivo. Silver iodide complexes at a concentration of 38 ppm of Ag in dry alfalfa substrate did not affect substrate digestion in vitro. Inhibition of rumen microbial digestion was noted with 100 or more ppm of Ag, as Ag NO₃, in an in vitro fermentation system. A chronic intake of 1 ppm of Ag in dry-matter intake did not produce gradual accumulation of Ag in the rumens of two goats. Silver passed from a goat rumen with a half time of 1.3 days. In two in vivo trials, neither suspensions of AgI complexes simulating 1 ppm of Ag in dry food intake nor solutions of AgNO₃ simulating 100 ppm of Ag in dry food intake inhibited rumen digestion rates. An abundance of chloride ions, proteins, bacteria and other organic matter precludes persistence of Ag ions in the rumen. Based on these results, Ag in forages in areas where clouds are seeded with AgI complexes, including areas near AgI generators, where forages rarely contain more than 1 ppm of Ag in dry matter, will not affect rumen microbial digestion.     

Development of an immunological technique for estimating mycelial biomass of Mycena galopus in leaf litter

Antisera were produced in rabbits against cell wall and cytoplasmic components of the mycelium of a litter-decomposing basidiomycete, Mycena galopus (Pers. ex Fr.) Kummer. The antisera were conjugated with fluorescein isothiocyanate, and positive reactions were obtained in direct and indirect fluorescent antibody (FA) tests with homologous antigens and with heterologous antigens of M. galopus from pure cultures and field material. Cross reactions occurred with fungal associates of M. galopus on Quercus litter from a deciduous woodland, but these were mostly removed by absorption with a preparation of Cladosporium herbarum Link ex Fr. Membrane filtration combined with FA staining and rhodamine-gelatin counter-staining was found to be a feasible means of estimating the biomass of FA-reactive mycelium of M. galopus in leaf litter.     

The elemental composition of asteroid 433 eros: results of the NEAR-shoemaker X-ray spectrometer

We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.     

Sounding the stratosphere and mesosphere by infrared limb scanning from space

Inversion of the measurements obtained by the infrared limb scanner on the Nimbus 6 satellite has demonstrated that the stratospheric and mesospheric temperatures and ozone concentrations may be obtained remotely from space with accuracy and precision comparable to in situ methods. Such global data have many applications in middle atmospheric research and operational temperature sounding.