Mechanism of broccoli-mediated verticillium wilt reduction in cauliflower.

ABSTRACT Broccoli is resistant to Verticillium dahliae infection and does not express wilt symptoms. Incorporation of broccoli residues reduces soil populations of V. dahliae. The effects of broccoli residue were tested on the colonization of roots by V. dahliae, plant growth response, and disease incidence of both broccoli and cauliflower in soils with different levels of V. dahliae inoculum and with or without fresh broccoli residue amendments. The three soils included a low-Verticillium soil, a high-Verticillium soil, and a broccoli-rotation soil (soil from a field after two broccoli crops) with an average of 13, 38, and below-detectable levels of microsclerotia per g of soil, respectively. Cauliflower plants in broccoli-amended high-Verticillium soil had significantly (P

Comparison of lettuce diseases and yield under subsurface drip and furrow irrigation.

ABSTRACT Subsurface drip and furrow irrigation were compared on lettuce (Lactuca sativa) cvs. Salinas and Misty Day for yield and incidence and severity of three important diseases of lettuce in the Salinas Valley, CA. Experiments were conducted between 1993 and 1995 during the spring and fall seasons. The diseases examined included lettuce drop (Sclerotinia minor), downy mildew (Bremia lactucae), and corky root (Rhizomonas suberifaciens). Replicated plots of subsurface drip and furrow irrigation were arranged in a randomized complete-block design. All plants were inoculated with S. minor at the initiation of the experiment during the 1993 spring season. Plots were not inoculated for downy mildew and corky root during any season nor were the plots reinoculated with S. minor. During each season, all plots were sprinkler irrigated until thinning, and subsequently, the irrigation treatments were begun. The furrow plots were irrigated once per week, and the drip plots received water twice per week. The distribution of soil moisture at two soil depths (0 to 5 and 6 to 15 cm) at 5, 10, and 15 cm distance on either side of the bed center in two diagonal directions was significantly lower in drip-irrigated compared with furrow-irrigated plots. Plots were evaluated for lettuce drop incidence and downy mildew incidence and severity at weekly intervals until harvest. Corky root severity and yield components were determined at maturity. Lettuce drop incidence and corky root severity were significantly lower and yields were higher in plots under subsurface drip irrigation compared with furrow irrigation, regardless of the cultivar, except during the 1994 fall season. Incidence and severity of downy mildew were not significantly different between the two irrigation methods throughout the study. The differential microclimates created by the two irrigation treatments did not affect downy mildew infection, presumably because the mesoclimate is usually favorable in the Salinas Valley. Subsurface drip irrigation is a viable, long-term strategy for soilborne disease management in lettuce in the Salinas Valley.

Development and Significance of Dicarboximide Resistance in Sclerotinia minor Isolates from Commercial Lettuce Fields in California.

Three growth stages of each of 20 Sclerotinia minor isolates were tested for resistance to iprodione. Sclerotia and both vegetative and mature mycelium of each isolate were plated on potato-dextrose agar (PDA) amended with 0, 1, 5, 10, 25, and 100 µg of the fungicide per ml, and radial growth was measured. All wild-type field isolates were initially sensitive and did not grow in the presence of iprodione. However, fungicide resistance arose readily in vitro. All 20 isolates produced measurable growth (≥2 mm) on iprodione at 5 µg/ml after 2 weeks when started from mature mycelium, and 18 of 20 isolates produced measurable growth after 4 weeks when started from vegetative mycelium. In general, fungicide-resistant growth arose more frequently and mean colony diameters were significantly greater (P ≤ 0.05) with mature mycelium than with vegetative mycelium at all times and concentrations. In sclerotial germination tests, at least 1% of sclerotia germinated in 18 of 20 isolates after 2 weeks on iprodione at 5 µg/ml, and in 19 of 20 isolates after 5 weeks on 100 µg/ml. Of growth produced on 79 plates containing iprodione, 73 remained viable on PDA after 5 months, and 71 retained resistance to 5 µg/ml. Seventy of these also exhibited cross-resistance to vinclozolin, another dicarboximide fungicide. Pathogenicity of five fungicide-resistant strains was tested in greenhouse, microplot, and field experiments, with and without iprodione. Two months after in vitro production, one of the five resistant strains was avirulent, but disease incidence for the other four ranged from 40 to 75%, compared with 40% for the wild-type isolates. However, the virulence of the fungicide-resistant strains declined over time. Ten months after their production, two of the isolates were avirulent and disease incidence for the others ranged from 3 to 17%, compared with 40 to 90% for the wild-type isolates. The strains that remained virulent 5 and 7 months after in vitro production were not significantly controlled by iprodione sprayed according to labeled rates, although disease was significantly controlled by the fungicide in treatments inoculated with wild-type field isolates (P > 0.05). In experiments in commercial fields to determine the efficacy of fungicide sprays on the wild-type S. minor population, there was no evidence that fungicide resistance was the cause of lack of lettuce drop control observed in many coastal California fields. Application of fungicides at a less than optimal time may account for some incidents of control failure.

Prevention of pulmonary emboli in hospitalized patients.

The risk of pulmonary infarction in any hospitalized population is high. To decrease this dreaded complication, the high risk population must be identified. These are chiefly elderly patients with a history of previous DVTP, cancer, cardiac disease, trauma to a lower limb or a history of recent surgery. All methods of reducing venous stasis should be used, and most of these patients should be treated prophylactically with subcutaneous heparin.

Non-specific incorporation of nucleic acid precursors in Blastomyces dermatitidis and Histoplasma capsulatum.

Incorporation of thymidine, thymidine monophosphate (TMP), thymidine triphosphate (TTP), uridine and orotic acid into DNA, RNA and protein in Blastomyces dermatitidis and Histoplasma capsulatum was studied utilizing a specific acid hydrolysis technique developed for these fungi. Thymidine was incorporated to the greatest extent (approximately 0.5% of added label) followed by uridine, orotic acid, TMP and TTP. In Blastomyces, uridine and orotic acid labeled primarily RNA. TMP and TTP labeled RNA, DNA and protein at nearly the same level. In Histoplasma RNA was labeled poorly by any of these precursors. TMP and TTP labeled DNA predominately and protein to a slightly lower level. Deoxyadenosine or uridine media supplements of 250 micrograms/ml did not enhance incorporation. All precursors tested were found to be nonspecific in that RNA, DNA and protein were labeled. All data indicate that neither RNA nor DNA synthesis can be specifically measured in whole cells or acid precipitates by any of these precursors. Specific radiometric monitoring with these isotopes therefore requires the separation of these macromolecules.

In Vitro and In Vivo Activity of a Synthetic Halogenated Quinoline Against Cryptococcus neoformans.

The minimum inhibitory concentrations of a halogenated quinoline, 3-amino-7-chloro-3,4-dihydro-1-hydroxycarbostyril (CBS), against nine clinical strains of Cryptococcus neoformans were determined by in vitro testing. The CBS was fungistatic at a minimum concentration of 0.2 mug/ml at 48 h for several strains. In vivo toxicity studies were carried out in mice. Mice were also infected with C. neoformans strain Price and injected with various concentrations of CBS. Mean life expectancy of treated groups of animals was increased over infected untreated controls.

Improved microscopy of Mycoplasma in vitro.

Techniques were developed for continuous microscopic observation of mycoplasmata growing in vitro in Rose chambers by using an inverted phase microscope. The methods permitted direct microscopic observation of undisturbed growth of mycoplasmata in liquid medium. Inocula of mycoplasmata were passed through 0.22-mum filters before culture to provide a suspension of discrete particles. The sequential growth of Mycoplasma pneumoniae was followed from points or single straight lines, with development of branching, a net-like confluence of filaments, large bodies occurring in the center of developing colonies, and finally coccoid forms. Other species of Mycoplasma which did not attach as readily to glass could be observed also by inverted phase microscopy. Umbonation of colonies (a "friedegg" appearance) occurred in liquid medium, indicating that this appearance was not due simply to interaction with the agar medium, but may reflect a qualitative difference in growth patterns between center and periphery. For growth on solid medium, direct observation of colonies in uncovered plates of agar medium was made by using inverted phase microscopy. This was found helpful in detecting small colonies and in observing relationships between colonies.