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Background and aims Resistant cultivars are one of the most effective control measures used against bacterial wilt, caused by the soilborne bacterium Ralstonia solanacearum. We aimed to determine the effect of temperature and resistance of tobacco varieties on bacterial wilt occurrence. Methods Five tobacco cultivars, with varying resistance levels, were inoculated and transferred to growth chambers at 10, 15, 20, 25, 30, and 35°C. The growth rate of R. solanacearum was also studied in culture at 10, 20, and 30°C. The mechanism of resistance was further examined in histological studies conducted at 10, 20, and 30°C with strain AW1-gfp38 that expresses green fluorescent protein.Results The highest disease incidence was observed at 30 and 35°C, while no symptoms were observed at 10 and 15°C. Strains grew in culture at all temperatures. At 30°C the low resistant cultivars had the most stems colonized by the bacterium, while the highly resistant cultivars mainly had localized infections in the roots. Conclusions We suggest that the mechanism of resistance in tobacco is associated with the ability to limit colonization of stem tissues and is temperature dependent. Evaluation of restricted root infections in breeding lines may provide a means for early screening of resistance in breeding programs.

Tar Spot continues to threaten U.S. corn production (Telenko et al., 2022). A reliable assay under controlled conditions is needed to study the epidemiology and management of Tar Spot. Researchers have reported controlled environment infections, but incidence and severity were low and the ability to screen germplasm has not yet been reported. In this paper, we describe a controlled environment assay that reliably achieves Tar Spot symptoms on corn plants allowing differentiation of susceptible and resistant germplasm.

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractMagnetic resonance (MR) logging was originally intended for measuring fluid filled porosity, and for differentiating between producible and non producible fluids. Early tools however came with special operational requirements. Wireline logs were slow and sensitive to wash-outs; early logging while drilling (LWD) measurements did not tolerate tool vibrations. Both required a good deal of preplanning to accommodate limited capability hardware. The paper shows how problems of the past could be solved by the innovative technology of Magnetic Resonance Logging While Drilling (MR-LWD).By returning to basics a new LWD magnetic resonance tool tolerant to vibration and easy to apply could be designed. The novel device acquires valuable data which can be used as well for formation evaluation as for geo-steering under normal drilling conditions and with standard operating practices. This was made possible by a short inter-echo spacing, by a special stabilization, and by a low magnetic field gradient. The new sensor operates with a minimum of preplanning and requires little to no interference with the drilling process.We present an application of the new system in a European onshore well. In the case described we show how reliable deliverables such as porosity and pore-size distribution can be determined from MR-LWD. Formation boundaries and fluid contact can easily be determined. The clear logs and the intuitive presentation of data makes MR while drilling ready for everyday petrophysics.

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractMagnetic resonance (MR) logging was originally intended for measuring fluid filled porosity, and for differentiating between producible and non producible fluids. Early tools however came with special operational requirements. Wireline logs were slow and sensitive to wash-outs; early logging while drilling (LWD) measurements did not tolerate tool vibrations. Both required a good deal of preplanning to accommodate limited capability hardware. The paper shows how problems of the past could be solved by the innovative technology of Magnetic Resonance Logging While Drilling (MR-LWD).By returning to basics a new LWD magnetic resonance tool tolerant to vibration and easy to apply could be designed. The novel device acquires valuable data which can be used as well for formation evaluation as for geo-steering under normal drilling conditions and with standard operating practices. This was made possible by a short inter-echo spacing, by a special stabilization, and by a low magnetic field gradient. The new sensor operates with a minimum of preplanning and requires little to no interference with the drilling process.We present an application of the new system in a European onshore well. In the case described we show how reliable deliverables such as porosity and pore-size distribution can be determined from MR-LWD. Formation boundaries and fluid contact can easily be determined. The clear logs and the intuitive presentation of data makes MR while drilling ready for everyday petrophysics.