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  • Author or Editor: R.O. Miller x
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Ornamentals, fruit and vegetable crops are commonly tested for inorganic anions, NO3-N, PO4-P, Cl and SO4-S, to identify the nutritional status of the plant. Two percent (0.20 M) acetic acid has primarily been used as the extractant for these inorganic anions. The use of acetic acid does not quantitatively extract SO4-S and PO4-P. Research using calcium formate was initiated to assess its effectiveness as an universal extractant for inorganic anions. Results of a series of experiments will be presented identifying the optimum calcium formate concentration, extraction time, and extractant sample ratio for quantitative removal and measurement of NO3-N, PO4-P, Cl and SO4-S. Results of spiking experiments will be presented using a range of horticultural crops important to California agriculture. Additional data will be presented on the use of calcium formate for the determination of K and NH4-N in botanical tissues.

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Since the discovery of elevated concentrations of selenium in the water, sediments, and biota at the Kesterson Wildlife Refuge, several studies regarding trace element distribution in the San Joaquin Valley and their potential environmental impacts have been initialed. We conducted a reconnaissance investigation to assess the concentration of boron, selenium, arsenic, molybdenum, uranium and vanadium using inductively coupled mass spectroscopy in prominent vegetation in the San Joaquin Valley. Five regions representing a range of geochemical environments with known differences in trace element concentrations in their soils or shallow ground water were selected for plant and soil sampling. Concentrations of boron, selenium arsenic, molybdenum, uranium, and vanadium in soil and tissue will be presented for these geographic areas for alfalfa, almonds, cotton, garlic, grapes, onions, tomatoes, and wheat. Interpretations of the wide range of trace element tissue concentrations that have been found will be discussed.

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Sustainable alternatives for saline drainage water management in areas such as California's San Joaquin Valley are needed. Previous work has demonstrated the short-term potential for reuse of saline drainage water for irrigation in this area. Results from our 6-year cyclic drainage reuse study, however, indicate that soil structural problems may occur which can greatly reduce stand establishment and crop yields in periodically salinized soils. To prevent these problems, we are evaluating the effectiveness of winter cover crop incorporation and gypsum applications relative to conventional fallows, for improving/maintaining soil physical properties and crop productivity in cyclically salinized soils. Six winter cover crop/fallow treatments have been imposed upon a rotation of tomatoes, tomatoes and cotton as summer crops. By monitoring water use, relevant soil physical and chemical properties as well as crop performance during the course of this 3-year rotation study, we are assessing the potential benefits and constraints of using winter cover crops in drainage water reuse systems.

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Our objective was to determine the feasibility of using waste tire rubber and fiber from the processing of waste tires as a root-zone medium for greenhouse crops. Two cultivars of zonal geraniums, `Danielle' and `Kim' were grown in media containing three grind sizes of rubber (10, 6, and 2.4 mm) and fiber from the fabric belting processed from waste tires in three proportions (1 rubber: 1 peat moss, 1 rubber: 1 vermiculite: 2 peat moss, and 2 rubber: 1 vermiculite: 1 peat moss, by volume). Two control media were also included: 1 vermiculite: 1 peat moss and 1 rock wool: 1 peat moss, by volume. The largest plants were grown in the 1 vermiculite: 1 peat moss medium, whereas the smallest plants were grown in the media containing the rubber grinds 2.4 mm and 6 mm making up 50% of the media. The media 1 rubber: 1 vermiculite: 2 peatmoss, regardless of grind or fiber, produced plants equal to the 1 rock wool: 1 peatmoss medium. All plants grown in media containing rubber by products had elevated levels of Zn and Cu in the foliage, but was greatest in media containing 50% rubber. Foliar P: Zn ratio was less for plants grown in media where rubber was 50% of the volume. The P: Zn ratio also was lower in plants grown in media with smaller grind sizes of rubber. Geranium plants can be successfully grown in media containing up to 25% rubber waste products without reducing plant quality.

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The Vigna Crop Germplasm Committee has established a core subset for the USDA cowpea germplasm collection. The subset consists of 9.3% (700 accessions) of the 7525 accessions currently contained in the collection. The subset was selected on the basis of country of origin, taxonomic characteristics, and known disease and pest resistance characteristics. Theoretically, the lines in the subset represent the genetic diversity present in the entire collection. A listing of the accessions in the subset is available from the Vigna germplasm curator (A.G. Gillaspie). The listing can also be accessed through the USDA's Germplasm Resources Information Network (GRIN).

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The udiA gene encoding the enzyme β -glucuronidase (GUS) appears promising as a genetic marker for early confirmation of successful plant cell transformation. Two strains of Agrobacterium rhizogenes and eight strains of A. tumefaciens were selected as hosts to carry a binary plasmid (pBI121) containing the marker gene encoding the GUS marker that is controlled by the CaMV35S promoter. Presence of plasmid pBI121 in the bacteria was confirmed by resistance to kanamycin, plasmid re-isolation, and restriction enzyme analysis. When the GUS enzyme was expressed in transformed plant cells, reaction with the histochemical substrate 5-bromo-4-chloro-3-indolylglucuronide (X-gluc) lead to blue pigment development. Expression of GUS in viable bacteria that had not been eliminated from transformed tissue caused problems with the early transformation detection in radish, peach, and apple stem sections by also producing a positive X-gluc color reaction. Putative transformation of apple xylem parenchyma callus was accomplished, as judged by resistance to kanamycin, opine analysis, GUS marker gene expression, and presence of the APH(3')11 enzyme. In this system, elimination of bacterial contamination was accomplished during multiple culture transfers on selective media. To be more useful as a marker, the GUS gene should be coupled with a promoter that will not be expressed by Agrobacterium. Parenchyma callus may serve as a primary screen to provide an efficient way of determining the ideal strain for transformation of deciduous tree fruit genera. In our studies, strain A281 consistently proved to be a vector superior to others tested.

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