Callus induction and plantlet formation from mature embryo cultures of Kentucky bluegrass (Poa pratensis L.) cultivars

The primary objectives of this study were to develop a suitable culture system and obtain plant regeneration from callus for Kentucky bluegrass (Poa pratensis L.) cultivars. Secondary objectives included (a) comparing the regenerability of cultivars differing in percent apomictic reproduction; (b) cytological investigation of chromosome numbers of regenerated plants; (c) testing incubation temperature effects on plant regeneration; and (d) determining the mode of plant regeneration from callus cultures. Mature embryos of seven Kentucky bluegrass cultivars were plated on a solid, modified Schenk and Hildebrandt medium in a series of three experiments. The first experiment, using the cultivar \u27South Dakota,\u27 tested the four synthetic auxins 2,4-D(2,4- dichlorophenoxyacetic acid), 2,4,5-T(2,4,5-trichlorophenoxyacetic acid, dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6- trichloropicolinic acid) at six different concentrations for callus induction and growth. Results indicated that dicamba at 20 μM and picloram at 60 μM produced the best callus growth and most shoot and root suppression. Using these auxin concentrations, a second experiment was conducted using seven cultivars with varying percentages of apomictic reproduction. Results indicated variation among cultivars and auxins in call using and plant regeneration with plantlet formation percentages being low (0%-3.1%). Somatic chromosome counts of regenerated plants and cultivar reference plants showed some varia-tion. No relationship was observed between percent apomictic reproduction and plant regenerability in the cultivars. A third experiment tested the effects of culture temperature (25°C vs. 15°C) and cold shock (4°C for 7 days) on plant regenera-tion from calli of the cultivars \u27A25 x Blacksburg\u27 and \u27Ram I\u27 using 20 μM dicamba. Culture at 15°°C improved plant regeneration over 25°C for both cultivars. Cold treatment at the 15°C culture temperature was not superior to no cold treatment for A25 x Blacksburg. Ram I demonstrated the highest percent plant regenera-tion at 15°C with a cold treatment (18.0%). A histological examination of calli in the latter two experiments showed the mode of plant regeneration to be organogenesis

EXTENSION PROGRAMS ON THE SOIL BANK

Teaching/Communication/Extension/Profession,

What Does It Cost To Dry Corn?

Returns from artificial drying vary from year to year, depending on weather and other conditions. But it\u27s possible to give a reasonably accurate picture of the costs to consider along with the advantages and disadvantages

FOREIGN AGRICULTURAL POLICY AND FAR EAST FARM MARKETS

Agricultural and Food Policy,

Estimating probability of germline mismatch repair mutations in colorectal cancer patients with microsatellite stable tumors

http://deepblue.lib.umich.edu/bitstream/2027.42/112938/1/13053_2011_Article_206.pd

Two clinical isolates of Mycoplasma hyosynoviae showed differing pattern of lameness and pathogen detection in experimentally challenged pigs

Mycoplasma (M.) hyosynoviae is known to colonize and cause disease in growing-finishing pigs. In this study, two clinical isolates of M. hyosynoviae were compared by inoculating cesarean-derived colostrum-deprived and specific-pathogen-free growing pigs. After intranasal or intravenous inoculation, the proportion and distribution pattern of clinical cases was compared in addition to the severity of lameness. Tonsils were found to be the primary site of colonization, while bacteremia was rarely detected prior to the observation of clinical signs. Regardless of the clinical isolate, route of inoculation, or volume of inocula, histopathological alterations and tissue invasion were detected in multiple joints, indicating an apparent lack of specific joint tropism. Acute disease was primarily observed 7 to 10 days post-inoculation. The variability in the severity of synovial microscopic lesions and pathogen detection in joint cavities suggests that the duration of joint infection may influence the diagnostic accuracy. In summary, these findings demonstrate that diagnosis of M. hyosynoviae-associated arthritis can be influenced by the clinical isolate, and provides a study platform to investigate the colonization and virulence potential of field isolates. This approach can be particularly relevant to auxiliate in surveillance and testing of therapeutic and/or vaccine candidates

The magnetic nature of disk accretion onto black holes

Although disk accretion onto compact objects - white dwarfs, neutron stars, and black holes - is central to much of high energy astrophysics, the mechanisms which enable this process have remained observationally elusive. Accretion disks must transfer angular momentum for matter to travel radially inward onto the compact object. Internal viscosity from magnetic processes and disk winds can in principle both transfer angular momentum, but hitherto we lacked evidence that either occurs. Here we report that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655-40 must be powered by a magnetic process that can also drive accretion through the disk. Detailed spectral analysis and modeling of the wind shows that it can only be powered by pressure generated by magnetic viscosity internal to the disk or magnetocentrifugal forces. This result demonstrates that disk accretion onto black holes is a fundamentally magnetic process.Comment: 15 pages, 2 color figures, accepted for publication in Nature. Supplemental materials may be obtained by clicking http://www.astro.lsa.umich.edu/~jonmm/nature1655.p

Two clinical isolates of \u3ci\u3eMycoplasma hyosynoviae\u3c/i\u3e showed differing pattern of lameness and pathogen detection in experimentally challenged pigs

Mycoplasma (M.) hyosynoviae is known to colonize and cause disease in growing-finishing pigs. In this study, two clinical isolates of M. hyosynoviae were compared by inoculating cesarean-derived colostrum-deprived and specific-pathogen-free growing pigs. After intranasal or intravenous inoculation, the proportion and distribution pattern of clinical cases was compared in addition to the severity of lameness. Tonsils were found to be the primary site of colonization, while bacteremia was rarely detected prior to the observation of clinical signs. Regardless of the clinical isolate, route of inoculation, or volume of inocula, histopathological alterations and tissue invasion were detected in multiple joints, indicating an apparent lack of specific joint tropism. Acute disease was primarily observed 7 to 10 days post-inoculation. The variability in the severity of synovial microscopic lesions and pathogen detection in joint cavities suggests that the duration of joint infection may influence the diagnostic accuracy. In summary, these findings demonstrate that diagnosis of M. hyosynoviae-associated arthritis can be influenced by the clinical isolate, and provides a study platform to investigate the colonization and virulence potential of field isolates. This approach can be particularly relevant to auxiliate in surveillance and testing of therapeutic and/or vaccine candidates

Homophily and Contagion Are Generically Confounded in Observational Social Network Studies

We consider processes on social networks that can potentially involve three factors: homophily, or the formation of social ties due to matching individual traits; social contagion, also known as social influence; and the causal effect of an individual's covariates on their behavior or other measurable responses. We show that, generically, all of these are confounded with each other. Distinguishing them from one another requires strong assumptions on the parametrization of the social process or on the adequacy of the covariates used (or both). In particular we demonstrate, with simple examples, that asymmetries in regression coefficients cannot identify causal effects, and that very simple models of imitation (a form of social contagion) can produce substantial correlations between an individual's enduring traits and their choices, even when there is no intrinsic affinity between them. We also suggest some possible constructive responses to these results.Comment: 27 pages, 9 figures. V2: Revised in response to referees. V3: Ditt