Vincent A. Fritz

Antibiotic uptake by vegetable crops from manure-applied soils.

This study quantified the uptake of five antibiotics (chlortetracycline, monensin, sulfamethazine, tylosin, and virginiamycin) by 11 vegetable crops in two different soils that were fertilized with raw versus composted turkey and hog manures or inorganic fertilizer. Almost all vegetables showed some uptake of antibiotics from manure treatments. However, statistical testing showed that except for a few isolated treatments the concentrations of all antibiotics in vegetable tissues were generally less than the limits of quantification. Further testing of the significant treatments showed that antibiotic concentrations in vegetables from many of these treatments were not significantly different than the corresponding concentrations from the fertilizer treatment (matrix effect). All five antibiotic concentrations in the studied vegetables were <10 μg kg(-1). On the basis of the standards for maximum residue levels in animal tissues and suggested maximum daily intake based on body weight, this concentration would not pose any health risk unless one is allergic to that particular antibiotic.

Green manures of oat, rape and sweet corn for reducing common root rot in pea (Pisum sativum) caused by Aphanomyces euteiches

Green manure crops of sweet corn, soybean, alfalfa, snap bean, rape, pea and of the two oat cultivars ‘Dane’ and ‘Troy’ were incorporated into the same soil and containers in which the crop had grown for five weeks. The soil was then evaluated for suppression of common root rot (Aphanomyces euteiches) of pea grown in infested pasteurized and non-pasteurized soils in the greenhouse. Pea biomass reduction and a plant bioassay for A. euteiches were used to measure the green manure suppression of disease. Green manures of sweet corn cv.‘Jubilee’, oat cv.‘Troy’, and rape cv.‘Humus’ significantly reduced pea biomass losses over the non-amended control soil treatments. Oat cv.‘Troy’and sweet corn cv.‘Jubilee’ green manures significantly reduced inoculum density of A. euteiches over the corresponding fallow controls in inoculated pasteurized soil by 87% and 76%, respectively, and in inoculated non-pasteurized soil by 67% and 66%, respectively. Only the green manure of oat cv. ‘Troy’ reduced inoculum density significantly below fallow.

Oat residue and soil compaction influences on common root rot (Aphanomyes euteiches) of peas in a fine-textured soil

Management of common root rot (Aphanomyces euteiches Drechs.) in peas (Pisum sativum L.) is sought primarily by host crop avoidance for several years. Soil compaction is known to aggravate A. euteiches disease in peas but effects on infection and subsequent symptom development are not sufficiently known to assist in cultural control. Several isolated observations have noted that oat crop residues may suppress A. euteiches infection and disease in pea roots. The individual and combined influence (a factorial combination of two factors each at two levels) of a prior oat crop and soil compaction were studied for their effects on common root rot severity in processing peas grown in an A. euteiches disease nursery on a fine-textured soil in the northern Corn Belt of the USA. A previous crop of summer oats relative to prior-year peas significantly suppressed common root rot and increased pea fresh vine weight 210% at peak bloom stage. Both fresh vine weight and green pea yield were reduced as much as 63% by soil compaction and increased as much as 48% by a prior oat crop. Greater soil bulk density at the 10 to 25-cm depth identified wheel traffic compaction patterns in each year. A 10-fold reduction of saturated hydraulic conductivity in the 10 to 25-cm compacted zone and high soil-water potentials within the upper 60 cm both confirmed an impaired water drainage, especially during infiltration events. These observations support the use of a previous full season or summer oat crop jointly with chisel plowing, plus the prevention of excessive traffic during secondary tillage and planting, to reduce common root rot in a field infested with A. euteiches. Shallow incorporation of oat shoot and root residue by chiseling could be a crucial component of the cultural control of the disease. R Rodriguez Kabana Section editor

Urinary 3,3′-Diindolylmethane: A Biomarker of Glucobrassicin Exposure and Indole-3-Carbinol Uptake in Humans

Background: Brassica vegetable consumption may confer a protective effect against cancer, possibly attributable to their glucosinolates. Glucobrassicin is a predominant glucosinolate and is the precursor of indole-3-carbinol (I3C), a compound with anticancer effects. However, objective assessments of I3C uptake from Brassica vegetables have not been successful. Methods: We conducted a randomized, crossover trial to test whether 3,3′-diindolylmethane (DIM, a metabolite of I3C) excreted in the urine after consumption of raw Brassica vegetables with divergent glucobrassicin concentrations is a marker of I3C uptake from such foods. Twenty-five subjects were fed 50 g of either raw “Jade Cross” Brussels sprouts (high glucobrassicin concentration) or “Blue Dynasty” cabbage (low glucobrassicin concentration) once daily for 3 days. All urine was collected for 24 hours after vegetable consumption each day. After a washout period, subjects crossed over to the alternate vegetable. Urinary DIM was measured using a novel liquid chromatography-electrospray ionization-tandem mass spectrometry–selected reaction monitoring (LC-ESI-MS/MS-SRM) method with [2H2]DIM as internal standard. Results: Urinary DIM was consistently and significantly higher after Brussels sprouts feeding than after cabbage feeding, as evidenced by an average difference of 8.73 pmol/mg creatinine (95% confidence interval, 5.36–12.10; P = 0.00002). Conclusion: We have successfully quantified urinary DIM after uptake of I3C from food, and demonstrated that differences in glucobrassicin exposure are reflected in urinary DIM levels. Impact: Our LC-ESI-MS/MS-SRM method and the results of our study indicate urinary DIM is a measure of I3C uptake from Brassica vegetables, a finding that can be utilized in prospective epidemiologic and chemoprevention studies. Cancer Epidemiol Biomarkers Prev; 23(2); 282–7. ©2013 AACR.

Research on cruciferous vegetables, indole‐3‐carbinol, and cancer prevention: A tribute to Lee W. Wattenberg

Lee W. Wattenberg, who spent his entire career at the University of Minnesota, was a true pioneer in the field of chemoprevention. This paper is a tribute to his groundbreaking research which uncovered the cancer prevention properties of many dietary compounds, including those discussed here in some detail-indole-3-carbinol and diindolylmethane. These compounds occur as glucosinolate conjugates in cruciferous vegetables and are released when one chews or otherwise macerates the vegetable. They have numerous beneficial effects including the ability to prevent cancer in laboratory animals treated with carcinogens. We review some of the early work on indole-3-carbinol and diindolylmethane which spurred subsequent studies on their efficacy and molecular mechanisms of prevention. We also present unique data on field conditions that affect levels of their glucosinolate precursors in vegetables and on the release of diindolylmethane in people who consume cruciferous vegetables.

Effect of Bacillus thuringiensis Application Interval on European Corn Borer (Lepidoptera: Pyralidae) Control in Sweet Corn

Ground-applied treatments of two commercial Bacillus thuringiensis subsp. kurstaki formulations (MVP and Dipel ES) and tank-mixes with a pyrethroid (Ambush 2E) were evaluated for control of European corn borer, Ostrinia nubilalis (Hubner), larvae in sweet corn. Treatments were applied at average intervals of 3.4, 5, 7, and 10 days to determine field persistence. Manual infestations of first-instar O. nubilalis were used to augment natural populations. During both years, there were no significant interactions between application interval and treatment for all dependent variables tested, including late instars per ear, percent marketability, yield, and predator density. Regardless of application interval, MVP provided greater larval control than Dipel ES. However, the decline in efficacy of the encapsulated MVP formulation occurred at the same rate as that of the non-encapsulated Dipel ES formulation over the 3.4 to 10-d intervals. Tank-mixes of B. thuringiensis + low-rate permethrin provided no additional ...

Harnessing the power of cruciferous vegetables: developing a biomarker for Brassica vegetable consumption using urinary 3,3'-diindolylmethane

Glucobrassicin in Brassica vegetables gives rise to indole-3-carbinol (I3C), a compound with potent anticancer effects in preclinical models. We previously showed that the urinary metabolite 3,3′-diindolylmethane (DIM) could discriminate between volunteers fed high and low doses of Brassica vegetables. However, the quantitative relationship between glucobrassicin exposure and urinary DIM level is unclear. We conducted a clinical trial to examine the hypotheses that a range of glucobrassicin exposure from Brassica vegetables is reflected in urinary DIM and that this effect plateaus. Forty-five subjects consumed vegetables, a mixture of brussels sprouts and/or cabbage, at one of seven discrete dose levels of glucobrassicin ranging from 25 to 500 μmol, once daily for 2 consecutive days. All urine was collected for 24 hours after each vegetable-eating session. Urinary DIM was measured using our published liquid chromatography-electrospray ionization-tandem mass spectrometry-selected reaction monitoring (LC/ESI-MS/MS-SRM) method. Urinary DIM excretion increased predictably with increasing glucobrassicin dose and plateaued between 200 and 300 μmol of glucobrassicin. The association between glucobrassicin dose and urinary DIM was strong and positive (R2 = 0.68). The majority of DIM was excreted in the first 12 hours after vegetable consumption. We conclude that urinary DIM is a reliable biomarker of glucobrassicin exposure and I3C uptake and that feeding glucobrassicin beyond 200 μmol did not consistently lead to more urinary DIM, suggesting a plateau in potential chemopreventive benefit. Cancer Prev Res; 9(10); 788–93. ©2016 AACR.

Seasonal variation in glucosinolate accumulation in turnips grown under photoselective nettings

Glucosinolates (GSLs) accumulation is greatly influenced by environmental conditions including planting date and light quality and quantity. Photoselective nettings influence both the quality and quantity of light transmitted onto the crop canopy. The objective of this study was to determine yield and GSL concentrations in turnip (Brassica rapa subsp. rapa L.) roots and shoots grown under different photoselective nettings at different planting dates. Field studies were conducted with red and white turnip cultivars at May and August planting dates for two years using blue, red, and yellow photoselective nettings and a no netting control. Netting did not significantly affect the shoot yield and had an inconsistent effect on root yield. Cultivars differed in GSL concentrations with JR, the white turnip cultivar, having the highest gluconapin (3-butenyl GSL) concentrations in root and shoot tissues and the red turnip cultivar having the highest total GSL concentration in root tissues. Netting did not significantly influence total or individual GSLs in root tissues. Netting was only a significant factor for glucobrassicanapin (GBN; 4-pentenyl GSL) concentration in shoots with no netting treatments resulting in the highest GBN concentrations. May plantings resulted in 50% higher total GSL concentrations than August plantings. Planting date × year interactions were significant for total and individual GSL concentrations. These interactions may be due to differences in mean air temperatures and solar radiation prior to harvest.

Common root rot of pea (Pisum sativum L.): Oat pre-crop and traffic compaction effects in fine-textured mollisols

Common root rot of pea caused by Aphanomyces euteiches Drechs. is widespread and difficult to control. In many production areas, yearly losses have been estimated at 10% because of the disease. Cultural control is needed even when disease tolerant cultivars are planted. Soil compaction due to traffic is known to aggravate the disease. In a series of research studies in a heavily infested nursery and adjacent farm fields, it was shown that compaction aggravates the disease by decreasing drainage and thus providing more favourable soil water conditions for early infection of pea roots. Traffic compaction has also provided an adverse abiotic environment for plant stress due to poor aeration. A precrop of oat (Avena sativum L.), as a full-season or late-summer crop, suppressed the disease only if the oat residue was incorporated at a shallow depth late in the fall using a chisel. Incorporated oat residue reduced inoculum potential of A. euteiches above 10 cm when incorporated with a chisel and below 10 cm when incorporated with a moldboard plow. A rolled towel bioassay using a susceptible pea cultivar successfully estimated inoculum potential when the test soil was placed near the epicotyl of 7-day-old seedlings. Although A. euteiches is an aggressive disease, all of these findings focus on vulnerability during the infection process. These investigations were required to examine carefully the soil ecology pertaining to the host crop, the pathogen when in the saprophytic mode, and the host crop interaction with the pathogen.

Alternatives to Atrazine for Weed Management in Processing Sweet Corn

Atrazine has been the most widely used herbicide in North American processing sweet corn for decades; however, increased restrictions in recent years have reduced or eliminated atrazine use in certain production areas. The objective of this study was to identify the best stakeholder-derived weed management alternatives to atrazine in processing sweet corn. In field trials throughout the major production areas of processing sweet corn, including three states over 4 yr, 12 atrazine-free weed management treatments were compared to three standard atrazine-containing treatments and a weed-free check. Treatments varied with respect to herbicide mode of action, herbicide application timing, and interrow cultivation. All treatments included a PRE application of dimethenamid. No single weed species occurred across all sites; however, weeds observed in two or more sites included common lambsquarters, giant ragweed, morningglory species, velvetleaf, and wild-proso millet. Standard treatments containing both atrazine and mesotrione POST provided the most efficacious weed control among treatments and resulted in crop yields comparable to the weed-free check, thus demonstrating the value of atrazine in sweet corn production systems. Timely interrow cultivation in atrazine-free treatments did not consistently improve weed control. Only two atrazine-free treatments consistently resulted in weed control and crop yield comparable to standard treatments with atrazine POST: treatments with tembotrione POST either with or without interrow cultivation. Additional atrazine-free treatments with topramezone applied POST worked well in Oregon where small-seeded weed species were prevalent. This work demonstrates that certain atrazine-free weed management systems, based on input from the sweet corn growers and processors who would adopt this technology, are comparable in performance to standard atrazine-containing weed management systems. Nomenclature: Atrazine; dimethenamid; mesotrione; tembotrione; common lambsquarters, Chenopodium album L.; giant ragweed, Ambrosia trifida L.; morningglory species, Ipomea spp.; velvetleaf, Abutilon theoprasti Medik.; wild-proso millet, Panicum miliaceum L.; sweet corn, Zea mays L.