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Deric D. Picton and Harrison G. Hughes

In this study, 11 species, hybrids, and color variants were characterized using randomly amplified polymorphic DNA (RAPD) analysis. Total genomic DNA was extracted using a 2% CTAB extraction buffer using fresh or frozen leaf material. The DNA was amplified using standard RAPD-PCR protocols utilizing 10-mer primers. All primers utilized exhibited a high degree of polymorphism in their banding patterns among the species and hybrids studied. The primers used produced ≈40 reproducible bands. It was possible to identify and uniquely distinguish all species and hybrids investigated using these bands.

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Francisco Lopez-Gutierrez, Harrison G. Hughes and Nicholas C. Carpita

After 6 months of growth in 200,400, and 500 mm NaCl, cultured cells of Distichlis spicata showed a decreased cell volume (size) despite maintenance of turgor pressure sometimes 2-fold higher than that of the control. Tensile strength, as measured by a nitrogen gas decompression technique, showed empirically that the walls of NaCl-stressed cells were weaker than those of nonstressed cells. Breaking pressures of the walls of control cells were ≈68 ± 4 bars, while that of the walls of cells grown in 500 mm NaCl (-25 bars) were 14 ± 2 bars. The relative amount of cellulose per cell remained about constant despite salt stress. However, glucuronoarabinoxylans were more readily extractable, presumably because of a decrease in cross-linkage with phenol substances. Therefore, we suggest that cellulose microfibrils are not the only determinants that confer tensile strength to the primary cell wall, but rather subtle changes in the matrix polysaccharides are likely responsible for this event.

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Chi Won Lee, Chun-Ho Pak and Harrison G. Hughes

Stevia (Stevia rebaudiana Bert.) leaves produce stevioside and rebaudioside that can be used as a natural source of low-calorie sweetener which is heat-stable. Because of low fertility, this plant is often vegetatively propagated for field production. This study was conducted to optimize tissue culture procedures for propagating selected clones and explore the feasibility of producing the sweetener compounds by callus cultures. Shoot proliferation was best in Murashige and Skoog (MS) medium supplemented with 0.1 mg/l naphthaleneacetic acid (NAA) Plus 10 mg/l kinetin. Kinetin as a cytokinin source was better than benzyladenine (BA) especially when NAA was present. Callus production fronm leaf disc cultures was most prolific when a combination of 0.1 mg/l NAA and 3 mg/l BA was used in MS medium. The relative sweetener contents of callus cultures are currently being-analyzed.

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Mekhled M. Alenazi, Harrison G. Hughes, Cecil Stushnoff and David G. Holm

The influence of storage temperature and length of time in storage on anthocyanin tuber concentration were investigated in seven potato genotypes. These genotypes were cultivars `All Blue' and `Yukon Gold' plus five selections that were various skin/flesh color types of red/red, purple/purple, white/yellow, and two red/yellow types. The red, blue, and purple colors are the result of various anthocyanin compounds. Tubers of the seven genotypes were stored at 4.4 or 10 °C for 0, 4, 6, 8, 10, 12, 16, 20, or 24 weeks. Both fresh and freeze-dried samples of the tubers were evaluated for each temperature and time treatment combination. Extractable anthocyanins were found in only the three pigmented genotypes red/red, purple/purple, and `All Blue'. Anthocyanin concentrations were estimated spectrophotometrically with a Molecular Devices Spectramax 384, based upon extinction coefficients reported in the literature for purple and red pigmented potatoes. Anthocyanin concentration increased in storage as time in storage increased for both fresh and freeze-dried samples. Tubers stored at the cooler temperature (4.4 °C) had higher levels of anthocyanin than those tubers stored at the higher temperature (10 °C). Increased levels of anthocyanins in cold-stored tubers may be linked to the conversion of starch to sugar (so called cold sweetening) known to occur at cold storage temperatures. Pigment extraction was more efficient from freeze-dried tuber samples compared to fresh tuber samples. There was, however, a similar increasing trend in both freeze-dried and fresh tuber sources with storage duration.

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Margaret L. Shore, Harrison G. Hughes, Frank D. Moore and Danny H. Smith

Carbonated water (CW) application has enhanced yields of tomato. However, little is known about the mechanism of this response. Our objectives were to determine if strawberry would respond to CW application and the effect of soil pH modification on the expression of a yield response. Two different soils were used; a calcareous soil (5% CaCO3, pH 7.9), with a Zn content 0.8 ppm and a non-calcareous soil (< 1% CaCO3, pH 6.5) with a Zn content 8.8 ppm. The carbonated water temporarily lowered the pH of the calcareous soil to 6.7 and the non-calcareous soil to 5.9, at both extremes of the optimal range (6.0-6.7) for strawberry. Application of carbonated water increased production of marketable fruit as compared to the tap water control on both soils, and the magnitude of the response to CW was similar for both soils. Soil and water treatment effects on leaf tissue Zn levels will also be discussed.