allyl isothiocyanate (AITC) break down in the soil, producing isothiocyanate, which is a potent biocide ( Ajwa et al., 2003b ; Rodriguez-Kabana (2005) ). Commercially, dazomet is mostly sold as solid granules and powder, which must be incorporated into
James P. Gilreath, Bielinski M. Santos, and Timothy N. Motis
Honghui Gu, Jiansheng Wang, Huifang Yu, Zhenqing Zhao, Xiaoguang Sheng, Jisuan Chen, and Yingjun Xu
been noted ( Zhang et al., 2011 ). Current research has demonstrated that the chemoprotective properties of cruciferous vegetables are attributed to GS hydrolysis products, primarily, isothiocyanates [ITCs ( Traka and Mithen, 2009 ; Verkerk et al
Akira Kitajima, Atsu Yamasaki, Tsuyoshi Habu, Bannarat Preedasuttijit, and Kojiro Hasegawa
rhodamine-conjugated anti-Dig and fluorescein isothiocyanate-conjugated avidin (La Roche Ltd.), respectively. Preparations were counterstained with DAPI and mounted in PPD. Chromosomes of GISH were photographed with an epifluorescence microscope (BX-FLA) and
Hyoung Seok Kim and John A. Juvik
GS degradation products. Among Brassica vegetables, broccoli is a rich source of GSs, phytochemicals that are hydrolyzed into isothiocyanates with known human anticarcinogenic bioactivity ( Talalay and Fahey, 2001 ). Broccoli has been considered as
Young-A Choi, R. Tao, K. Yonemori, and A. Sugiura
Multi-color genomic in situ hybridization (MCGISH) was performed for mitotic cells of the somatic hybrids of Diospyros kaki (2n = 6x = 90) and D. glandulosa (2n = 2x = 30). Total DNA of D. kaki and D. glandulosa were isolated and labeled with biotin-16-UTP and digoxigenin (DIG)-11-UTP, respectively. The labeled DNAs were used as probes to differentiate parental chromosomes. The biotin-labeled probe was detected with avidin-rhodamine, and the DIG-labeled probe was detected with anti-DIG-FITC (fluorescein isothiocyanate). Ninety chromosomes from D. kaki that showed reddish-orange and 30 chromosomes from D. glandulosa that showed greenish-yellow were observed under a fluorescence microscope. Some chromosomes showed cross-hybridization with both probes at their terminal or other chromosome regions. These results indicated that MCGISH could be used to analyze genomes of Diospyros species whose chromosomes are small and numerous.
Timothy J Ng and James G. Kantzes
Twenty-five melon (Cucumis melo L.) cultigens were screened for resistance to fusarium wilt in a field infested with race 1 and race 2 of Fusarium oxysporum f.sp. melonis in 1993 and 1994. Plants were grown on clear plastic mulch using commercial production recommendations. The soil was fumigated with methyl isothiocyanate at a broadcast rate of 340 liters·ha–1 in 1993, and with dichloropropene at a broadcast rate of 136 liters·ha–1 in 1994. Resistance was determined by the percentage of plants surviving 8 weeks after transplanting. In general, highly resistant cultigens (>90% survival) and highly susceptible cultigens (<20% survival) performed consistently in the two experiments. However, differences in performance between the two years were noted for cultigens with intermediate resistance, and their performance may have contributed to the significant cultigen × year interaction in this study.
Jed W. Fahey and Paul Talalay
High fruit and vegetable consumption is associated with a striking reduction in susceptibility to malignancy. In addition to other health benefits (e.g., high levels of vitamin C, carotenoids, and dietary fiber), cruciferous vegetables contribute significantly to this chemoprotective effect. Cruciferous vegetables (e.g. Brassica sp.), contain glucosinolates, water-soluble secondary metabolites that are converted to highly reactive isothiocyanates as a defense response to predation or injury. When fed to mammals, isothiocyanates induce Phase 2 enzymes such as glutathione-S-transferase and quinone reductase, that detoxify xenobiotics. Phase 2 enzyme induction potential was assessed for fruits and vegetables from a wide variety of plant families and the Brassica vegetables were particularly rich in such activity. Tremendous variability in glucosinolate content and Phase 2 enzyme induction potential was found between commercial broccoli cultivars (n = 12) and between sites (n = 7) growing transplants produced at the same time, from the same seedlot. Broccoli (B. oleracea var. italica) cvs. Green Comet and Excelsior had an almost identical spatial distribution of Phase 2 enzyme induction potential that varied by position on market-stage plants. Fertilization regime also affected Phase 2 enzyme induction by these two cultivars. Additionally, induction of detoxication enzymes and glucosinolate profiles have been evaluated in primary and axillary shoots of two greenhouse-grown broccoli cultivars (Broccolo Natalino and a proprietary hybrid), harvested over the duration of a 2-month period of side-shoot production. This approach to evaluating the germplasm, positional, temporal, and cultural effects on levels of inducers of mammalian detoxication enzymes should lead to development of cultivation strategies to enhance the chemoprotective effect of Cruciferous vegetables.
Husein A. Ajwa and Thomas Trout
Strawberry (Fragaria ×ananassa Duchesne) is a high-value cash crop that benefits from preplant soil fumigation with methyl bromide (MB) and chloropicrin (CP). Methyl bromide will be banned in the U.S. and other developed countries by 2005 for most uses. Potential alternative chemicals to replace methyl bromide for soil fumigation include CP, 1,3-dichloropropene (1,3-D), and methyl isothiocyanate (MITC) generators such as metam sodium (MS). Commercial formulations of these fumigants applied singly and in combination through drip irrigation systems were evaluated at two sites for three consecutive growing seasons as alternatives to MB:CP fumigation for strawberry production. A mixture of 1,3-D and CP was shank injected as Telone C35 (62% 1,3-D and 35% CP) at 374 kg·ha-1. An emulsifiable concentrate (EC) formulation of 1,3-D and CP was applied as InLine (60% 1,3-D and 32% CP) at 236 and 393 L·ha-1 through drip irrigation systems in three amounts of irrigation water (26, 43, and 61 L·m-2). Chloropicrin (CP EC, 96%) was drip applied singly at 130 or 200 L·ha-1. Metam sodium was applied singly as Vapam HL in three amounts of water and in combination with InLine and CP EC. Strawberry growth, fruit yields, disease pressure, and weed biomass were compared to an untreated control and shank injection with MB:CP mixture (67:33) at 425 kg·ha-1. For soils high in pathogen populations, fruit yield from the untreated plots was 34% to 50% relative to the MB:CP treatment. The greatest (95% to 110%) yields relative to MB:CP were in the high rates of the InLine treatments. Yields from simultaneous drip fumigation with a combination of Vapam HL and InLine or CP EC were less (67% to 79%) than yields from shank fumigation with MB:CP due to 1,3-D and CP hydrolysis reactions with Vapam HL or the generated MITC in the irrigation water that reduced the efficacy of these combinations to control soilborne pathogens. Application of reduced rates of InLine or CP EC followed 6 days later with reduced rates of Vapam HL controlled soil borne pathogens and weeds and produced the greatest fruit yield relative to all treatments. Chemical names used: 1,3-dichloropropene (1,3-D); methyl bromide (MB); trichloronitromethane (chloropicrin, CP); sodium methyldithiocarbamate (metam sodium); methyl isothiocyanate (MITC).
Steven Vaughn*, Terry Isbell, David Weisleder, and Mark Berhow
Field pennycress (Thlaspi arvense L.) seedmeal was found to suppress seedling germination/emergence and biomass accumulation when added to a sandy loam soil containing wheat (Triticum aestivum L.), arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] and sicklepod (Senna obtusifolia (L.) H.S. Irwin & Barneby) seeds. Covering the pots with petri dishes containing the soil-seedmeal mixture increased phytotoxicity at the lowest application rate, suggesting that the some of the phytotoxins were volatile. Dichloromethane, methanol and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod radicle elongation. Only the dichloromethane extract was found to be strongly inhibitory to both species. Fractionation of the dichloromethane extract identified two major phytotoxins, identified by GC-MS and NMR analyses as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, the germination of all three species were completely inhibited by both compounds at concentrations of 5 ppm or less.
Chien Wang, Korakot Chanjirakul, Shiow Wang, and Jingtair Siriphanich
The effect of naturally occurring volatile compounds on decay and antioxidant activities in fresh-cut papayas (Carica papaya L.) was studied. Exposure to methyl jasmonate (MJ), methyl salicylate (MS) or allyl isothiocyanate (AITC) substantially delayed the onset and reduced the severity of decay during and after storage at 5 °C. Treatment with tea tree oil (TTO) or ethanol (ETOH) was also effective in retarding decay, but to a lesser extent. No beneficial effect was obtained with the use of vinegar vapor. MJ and MS increased oxygen radical absorbance capacity and elevated the activities of several antioxidant enzymes, including glutathione reductase, glutathione peroxidase, guaiacol peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and superoxide dismutase. The nonenzyme components in the ascorbate-glutathione cycle were also increased by MJ and MS treatments, including ascorbate and glutathione. It is possible that MJ and MS treatments enhanced the antioxidant system and increased the resistance of tissue to decay. However, while AITC also suppressed the development of decay in papaya slices, it had little effect on antioxidant levels and antioxidant enzyme activities. Apparently, AITC exerted its effect through different mechanisms. Studies are in progress to determine if AITC inhibits decay directly via its antimicrobial properties.