The U.S. Department of Agriculture (USDA) pepper (Capsicum spp.) germplasm collection contains several thousand members or accessions. Many of these species and cultivars have not been analyzed for their concentrations of ascorbic acid, capsaicin, and total phenolic compounds, which are important antioxidants having a number of benefits for human health. The objective of this investigation was to select candidate accessions of hot pepper having high concentrations of ascorbic acid, capsaicin, free sugars, and total phenols for use as parents in breeding for these compounds. Seventeen accessions of pepper from the core Capsicum germplasm collection (four accessions of Capsicum chinense; five accessions of C. baccatum; six accessions of C. annuum; and two of C. frutescens) were field grown and their mature fruits were analyzed for their antioxidant composition. Concentrations of these compounds tended to be higher in C. chinense and C. baccatum, than in C. annuum and C. frutescens. Across all accessions the concentration of total phenols was correlated with ascorbic acid (r = 0.97) and free sugars (r = 0.80). Concentrations of total phenols (1.4, 1.3, and 1.3 mg g⁻¹ fruit) and ascorbic acid (1.6, 1.2, and 1.3 mg g⁻¹ fruit) were significantly greater in PI-633757, PI-387833, and PI-633754, respectively, compared to other accessions analyzed. Total capsaicinoids concentrations were greatest (1.3 mg g⁻¹ fruit) in PI-438622 and lowest (0.002 mg g⁻¹ fruit) in Grif-9320. The great variability within and among Capsicum species for these phytochemicals suggests that these selected accessions may be useful as parents in hybridization programs to produce fruits with value-added traits.

Soil enzymes (urease, invertase, acid and alkaline phosphatase) activity in the rhizosphere of field-grown tomato plants were used to monitor the impact of soil amendments (SA) and SA mixed with biochar on soil microbial activity four months after addition of amendments. The soil treatments were sewage sludge (SS); horse manure (HM); chicken manure (CM); vermicompost (worm castings); commercial inorganic fertilizer; commercial organic fertilizer; and no-mulch (NM) native soil used for comparison purposes. Soil treatments also were mixed with 10% (w/w) biochar to investigate the impact of biochar on soil enzymes activity. The results showed a significant increase in soil urease and invertase activities after incorporation of SA to native soil. Vermicompost and HM were superior in increasing urease and invertase activity four months after their addition to native soil. Alkaline phosphatase activity fluctuated among the soil treatments, revealing some obstruction of its activity. SS amended with biochar increased acid phosphatase activity by 115% four months after SS addition. Other than alkaline phosphatase, organic manure enhanced soil biological activity (microbial biomass and release of enzymes), indicating that the use of manures, rather than inorganic fertilizers, in crop production is an affordable and sustainable agricultural production system.

Glucosinolates (GSLs), a group of compounds found in Brassica plants, are toxic to some soil-borne plant pathogens because of the toxicity of their hydrolysis products, isothiocyanates. Other phytochemicals found in Brassica plants, such as phenols and ascorbic acid, may compliment the activity of GSLs. A survey of Brassica accessions from the national germplasm repository was conducted to identify potential cover crops that could be soil-incorporated for use as biofumigants. Ten Brassica accessions that demonstrated relative cold tolerance, rapid maturity, and superior biomass production were selected. The selected accessions were grown under three climatic conditions (fall greenhouse, winter high tunnel, and spring field) to investigate whether growing conditions affect their GSL, phenol, and ascorbic acid content. The selected accessions included seven accessions of Brassica juncea (Indian mustard), one of Brassica napus (oil seed rape), one of Brassica campestris (field mustard), and one of Eruca sativa (arugula). Separation of GSLs from the selected Brassica accessions was achieved using ion-exchange sephadex in disposable pipette tips. Quantification of total GSLs was based on inactivation of the endogenous thioglucosidase and liberation of the glucose moiety from the GSL molecule by addition of standardized thioglucosidase (myrosinase) and colorimetry. GSL concentration of greenhouse, high tunnel, and field-grown shoots (leaves and stems) averaged 24, 40 and 76 μ moles g^{− 1} fresh weight, respectively. Accessions of B. juncea generally had the highest GSL content. A comparison of accessions revealed that Ames 8887 of B. juncea contained the greatest GSL concentration, but had the lowest biomass yield and ascorbic acid concentration, in part because phytochemical concentration tended to be negatively correlated with biomass yield. More promising was B. juncea accession ‘Pacific Gold’ which coupled high biomass yield with above-average GSL production, but had low phenol and ascorbic acid concentration. We concluded that environmental stress on growing plants can increase the concentration of GSLs, ascorbic acid, and total phenols in Brassica shoots, but does not increase yields of these phytochemicals per unit area.

The mobility of heavy metals from soil into the food chain and their subsequent bioaccumulation has increased the attention they receive as major environmental pollutants. The objectives of this investigation were to: i) study the impact of mixing native agricultural soil with municipal sewage sludge (SS) or chicken manure (CM) on yield and quality of cabbage and broccoli, ii) quantify the concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in soil amended with SS or CM, and iii) determine bioavailability of heavy metals to cabbage leaves and broccoli heads at harvest. Analysis of the two soil amendments used in this investigation indicated that Cr, Ni, Cu, Zn, Mo, Cd, Pb, and organic matter content were significantly greater (P < 0.05) in premixed sewage sludge than premixed chicken manure. Total cabbage and broccoli yields obtained from SS and CM mixed soil were both greater than those obtained from no-mulch (bare) soil. Concentration of Ni in cabbage leaves of plants grown in soil amended with CM was low compared to plants grown in no-mulch soil. No significant differences were found in Cd and Pb accumulation between cabbage and broccoli. Concentrations of Ni, Cu, Zn, and Mo were greater in broccoli than cabbage. Total metals and plant available metals were also determined in the native and amended soils. Results indicated that the concentration of heavy metals in soils did not necessary reflect metals available to plants. Regardless of soil amendments, the overall bioaccumulation factor (BAF) of seven heavy metals in cabbage leaves and broccoli heads revealed that cabbage and broccoli were poor accumulators of Cr, Ni, Cu, Cd, and Pb (BAF 1 for Zn and Mo. Elevated Ni and Mo bioaccumulation factor (BAF >1) of cabbage grown in chicken manure mixed soil is a characteristic that would be less favorable when cabbage is grown on sites having high concentrations of these two metals.

The use of sewage sludge as a source of nutrients in crop production is increasing in the United States and worldwide. A field study was conducted on a 10% slope at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge, six plots were mixed with yard waste compost, and six unamended plots were used for comparison purposes. During a subsequent 3-year study, plots were planted with potato (year 1), pepper (year 2), and broccoli (year 3). The objectives of this investigation were to: (i) characterize chemical properties of soil-incorporated sewage sludge and yard waste compost; (ii) determine the concentration of seven heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) in sewage sludge and yard waste compost used for land farming; and (iii) monitor heavy metal concentrations in edible portions of plants at harvest. Concentrations of heavy metals in sewage sludge were below the U.S. EPA limits. Analysis of potato tubers, peppers, and broccoli grown in sludge-amended soil showed that Cd, Cr, Ni, and Pb were not significantly different from control plants. Concentrations of Zn, Cu, and Mo were significantly greater in tubers and peppers grown in sludge compared to their respective controls. Zn and Mo in broccoli heads were higher than their control plants. The ability of potato to accumulate lead needs additional investigation to optimize the phytoremediation of this pollutant element.

Increasing concern about persistence and environmental impact of synthetic pesticide residues require development of biodegradable and environmentally safe alternatives. The potential of using fruit extracts of hot pepper as alternatives to synthetic acaricides for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study. Twenty-four Capsicum accessions (Solanaceae) were screened for their toxicity and repellency to the spider mites. Crude extracts from fruits of C. chinense, C. frutescens, C. baccatum, C. annuum, and C. pubescens were prepared in methanol and tested for their acaricidal properties. Spider mite mortality was greatest (45%) when fruit extract of accession Grif-9169 (C. annuum) was used. Results from diving board bioassays indicated that mites avoided filter paper strips treated with hot pepper extracts from accessions PI-596057 (C. baccatum), PI-195299 (C. annuum), and Grif- 9270 (C. annuum). This investigation suggests that methanolic extracts of these three accessions may have a great potential for repelling spider mites and should be field-tested on a large-scale to assess their value in managing populations of spider mites, which could reduce reliance on synthetic acaricides. An attempt was made to correlate repellency with chemical constituents of fruit extracts of the most repellent accessions to identify chemical sources of repellency. Capsaicin and dihydrocapsaicin, the pungent components of pepper fruit, were not correlated with toxicity or repellency, indicating that these are not likely related to the toxicity or repellency of the pepper fruit extracts. Other, unidentified chemicals are likely responsible for toxicity and repellency to the two-spotted spider mite