Abstract. Universities, experiencing growths in student enrollment and reductions in operating budgets, are faced with the problem of providing adequate help resources for students. Help resources are needed at an institution-wide and also at a course-specific level, due to the limited time of instructors to provide help and answer questions. The Intelligent IntraNet Peer Help Desk provides an integration and application of previously developed ARIES Lab tools for peer help to university teaching. One of its components, CPR, provides a subject-oriented discussion forum and FAQ -list providing students with electronic help. Another component, PHelpS, suggests an appropriate peer to provide human help. In both cases it is peer help, since the help originates from students themselves. The selection of the appropriate help resource (electronic or human) is based on modelling student knowledge and on a conceptual model of the subject material.

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A monoclonal antibody, designated AbF21-1D3G7C8, reacts in useful for laboratory diagnosis of A. tumejaciens biovar 3, and thus for enzyme-linked immunosorbent assay with biovar 3 strains of detection and diagnosis of grapevine crown gall, indexing of propagation Agrobacterium tumefaciens, causal agent of grapevine crown gall, from wood, and quarantine testing. A. tumeJaciens biovar 3 was identified North America, Europe, and Asia, regardless of tumorigenicity.

Host (Vitis vinifera 'Chardonnay') and nonhost (Avena sativa 'Astro') tumors, and systemic infections were detected in 10%. Populations of rhizospheres enhanced survival of Agrobacterium tumefaciens biovar 3 rifampicin-resistant AT3 did not change over 10 wk in Concord grapevine (AT3) in artificially infested unpasteurized field soil in a greenhouse study; (Vitis labrusca L.) rhizosphere; 60% of Concord seedlings in soil infested populations in host rhizospheres were greater than in nonhost with 106 cfu/gbecame systemically infected within l0wk, but none became rhizospheres. Populations declined over time in both fallow soil and oat systemically infected at lower levels of soil infestation (104, 102, and I rhizospheres but not in grapevine rhizospheres. AT3 survived 10 mo in cfu/g). association with 54% of grapevines assayed; 35% of these developed Agrobacterium tumefaciens (E. F. Smith & Townsend) Conn pin through the smear several times to wound the stem. Soil (sandy biovar 3 (AT3) is associated with crown gall of grapevine (Vitis loam collected from an apple nursery) was infested with 1% (v/w) spp.) throughout the world (5,9,12,15,17-19). AT3 survives suspensions of 4-day-old PDA cultures of CG48 or CG49 in saprophytically as systemic infections in grapevine xylem and is distilled water adjusted to A 6 0 0 nm = 0.1, approximately 108 cfu transmitted to new plantings by vegetative propagation of (colony-forming units)/ ml (estimated by dilution plating), or 1% grapevine cuttings (6,13,20). Tumor induction follows wounding (w/w) gall tissue (approximately 106 cfu/g, estimated by diluting of systemically infected grapevines by sudden drops in temperature plating) comminuted in an electric coffee grinder. Control soils or mechanical means (3,9,13,14). were treated with distilled water (1%, v/w) in each experiment. Testing of grapevine propagation stocks and production of V. vinifera'Chardonnay'plants, freed of AT3 by propagation of AT3-free grapevines have been proposed as approaches to disease shoot tip cultures in vitro (8), were transplanted one per 8-cm pot in control (1,6,8,20). Success of these control strategies will depend infested and control soils when several leaves had expanded and on continued freedom of grapevines from AT3 after planting in the shoots were 3-5 cm in length. Nine oat (Avena sativa L. 'Astro') field. AT3 appears to be restricted to soils where grapevines have seeds per 8-cm pot were sown 1 cm deep. Plants were maintained in grown (5,7), indicating that AT3 is introduced with diseased or a greenhouse (approximately 24 C, 16-hr photoperiod) and were systemically infected propagation material. Survival of AT3 in soil watered daily with approximately 9 ml of distilled water. apart from grapevines and infection of grapevines by soilborne Three replicates each of infested and control treatments were AT3 have not been described. sampled, as described below, at the time of infestation and 3, 14, Our objectives were to compare the survival of AT3 in host and 28, and 70 days after infestation an...

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