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Taxol® (paclitaxel), an important anticancer agent, is found in many species of yew. As the need for Taxol increases, sustainable sources must be found for this drug. Plants often respond to stress with increased production of terpenoid compounds such as Taxol and related taxanes or hormones such as abscisic acid (ABA). To determine whether water stress would enhance the production and recovery of Taxol from stem clippings, 100 young Taxu×media `Hicksii' shrubs were grown for sustainable production of Taxol from stem clippings for two seasons in the dry climate of the Malheur Experiment Station in Ontario, Ore. Shrubs were grown under minimal, moderate, or severe water stress, and the relationships between taxane content and 1) soil and plant water potentials, 2) percentage of stomatal closure, and 3) ABA content were examined. Severely water-stressed shrubs produced significantly more taxanes and ABA than did the less stressed shrubs. Chemical names used: Taxol; 10-deacetyl baccatin III; baccatin III; 10-deacetyl taxol, cephalomannine; 7-epi; 10-deacetyl taxol; abscisic acid. Taxol is a registered trademark of Bristol-Myers Squibb.
Eight winter squash varieties (Table Ace Acorn, Sweet Dumpling, Waltham Butternut, Honey Boat, Sugar Loaf, Spaghetti, Gold Keeper, and Kabocha) were placed in storage 3 weeks after harvested and were stored for 6, 12, or 16 weeks at 5, 10, or 15°C and 50, 60, or 70 percent relative humidity. Before storage Spaghetti squash had low dry weight and low sugars while Kabocha, Sugar Loaf, and Honey Boat had high dry weight and high sugars. Squash of all varieties suffered high spoilage when stored at 5°C. Water losses increased with temperature or with storage at 50 percent relative humidity. Considering both spoilage and water loss, marketable fruit was highest when squash was stored at 10°C or 15°C and 60 or 70 percent relative humidity. Squash sugars were maintained with storage at 5°C and 10%. Squash can be stored for several months at 10°C and 60 to 70 percent relative humidity with little fruit loss or loss of sugar.
Onion (Allium cepa L.) production in the Treasure Valley of eastern Oregon and southwestern Idaho has been based on furrow irrigation with 318 kg·ha-1 N fertilizer and average yields of 70 Mg·ha-1, but these practices have been implicated in nitrate contamination of groundwater. Drip irrigation, introduced in the early 1990s, has several advantages, including reduced leaching losses. Since onion plant populations and N fertilizer rates can affect economic returns, studies were conducted in 1999, 2000, and 2001 to determine optimum plant populations and N fertilizer rates for subsurface drip-irrigated onion. Long-day onion (`Vision') was subjected to a combination of seven nitrogen fertilization rates (0 to 336 kg·ha-1 in 56-kg increments applied between late May and early July) and four plant populations (185, 250, 300, and 370 thousand plants/ha). Onion was grown on silt loam in two double rows spaced 0.56 m apart on 1.1 m beds with a drip tape buried 13 cm deep in the bed center. Soil water potential was maintained nearly constant at -20 kPa by automated irrigations based on soil water potential measurements at a 0.2-m depth. Onion bulbs were evaluated for yield and grade after 70 days of storage. Onion yield and grade were highly responsive to plant population. Onion marketable yield increased, and bulb diameter decreased with increasing plant population. Within the range of plant populations tested, gross returns were not always responsive to plant population. Returns were increased by the increase in marketable yield obtained with higher plant population, but higher plant population also reduced the production of the largest sized bulbs which had the highest value per weight. Onion yielded 95 Mg·ha-1 with no applied N fertilizer, averaged over plant populations and years. Onion yield and grade were not responsive to N fertilizer rate or interaction of N fertilizer rate with plant population. Preplant soil available N, N mineralization, and N in irrigation water all contributed N to the crop. Onion N uptake did not increase with increasing N fertilizer rate.
Eleven treatments in 1999 and thirteen treatments in 2000 containing single or combined nonconventional additives from eight manufacturers were compared with an untreated check for their effect on onion (Alliumcepa L.) yield and quality, and for their economic efficiency. The nonconventional additives were tested at commercial rates using the methods of application provided by the manufacturers. The products were applied to soil, foliage, or both. The treatments, including the check, were incorporated into standard cultural practices for onions. All treatments (with exception of an organic fertilizer treatment), including the check, were fertilized based on soil tests. In both years, none of the products evaluated significantly increased onion yield or quality compared to the untreated check. The organic fertilizer treatment, tested in 1999 only, resulted in significantly lower onion yield and size compared to the check. At the application rates used in this study, most of the products supplied plant nutrients or humic acid in amounts insufficient to expect improvements in crop production.
Sweet worm wood is a source of the anti-malarial plant secondary compound artemisinin. The effects of water stress, nitrogen rates, plant growth regulators, and harvest timing on vegetative growth and yield of artemisinin were tested in separate experiments. In the harvest timing trial, total biomass, leaf yield, leaf artemisinin content and total artemisinin yield increased during the season. The wettest treatment tested decreased the total plant dry to fresh weight ratio, but had no effect on height, total biomass, leaf yield, leaf artemisinin content and artemisinin yield. Nitrogen fertilization increased plant height, but had no effect on total biomass, leaf yield, leaf artemisinin content and artemisinin yield. The plant growth regulators decreased plant height, increased total biomass, but had no effect on leaf yield, leaf artemisinin content and artemisinin yield. The effects of chemical weed control and post-harvest leaf drying will also be discussed.
Onion (Allium cepa) cultivars for commercial production in eastern Oregon and southwestern Idaho are evaluated annually in replicated yield trials conducted at the Malheur Experiment Station, Oregon State University, Ontario. Market demand has progressively called for larger bulb size and bulbs with single centers. At harvest onions were evaluated for maturity, number of bolters, and single centeredness. Cultivars showed a wide range of bulbs with only one growing point or “bullet” single centers, ranging from 1% to 57% in 2000, from 7% to 70% in 2001, and from 1% to 74% in 2002. The percentages of bulbs functionally single-centered for processing uses ranged from 18% to 88% in 2000, from 24.7% to 91.3% in 2001, and from 14.4% to 92% in 2002. Bulb yield and market grade were evaluated out of storage. Marketable yield after 4 months of storage varied significantly by cultivar from 643 to 1196 cwt/acre (72.1 to 134.1 Mg·ha–1) in 2000, from 538 to 980 cwt/acre (60.3 to 109.8 Mg·ha–1) in 2001, and from 583 to 1119 cwt/acre (65.3 to125.4 Mg·ha–1) in 2002. Averaging over cultivars, super colossal bulb size averaged 26%, 14%, and 10% in 2000, 2001, and 2002, respectively.
Although an irrigation onset criterion for drip-irrigated onion (Allium cepa) has been determined, the optimal irrigation intensity has not been examined. Some authors have argued that very high irrigation frequencies with low amounts of water are needed to maximize crop responses. Long-day, sweet Spanish onions were grown on 44-inch beds with two double rows spaced 1.8 ft apart and a drip tape buried 4 inches deep in the bed center. Onions were submitted to eight treatments as a combination of four irrigation intensities (1/16, 1/8, 1/4, and 1/2 inch of water per irrigation) and two drip tape emitter flow rates (0.5 and 0.25 L·h–1) on silt loam in 2002 and 2003. The 1/16-, 1/8-, 1/4-, and 1/2-inch irrigation intensities had irrigations scheduled up to eight times, four times, twice, or once per day, respectively, to replenish soil water potential to –20 cbar as needed. Each plot was independently and automatically irrigated if the soil water potential at 8-inch depth was equal to or lower than –20 cbar. This resulted in an average of 564, 269, 121, and 60 irrigations over 107 days for the 1/16-, 1/8-, 1/4-, and 1/2-inch irrigation intensities, respectively. Onions were harvested, stored, and evaluated for yield and grade after 75 days of storage. Averaged over irrigation intensities, the drip tape with 0.5 L·h–1 emitters had significantly higher total yield, marketable yield, and colossal onion yield than the tape with 0.25 L·h–1 emitters. Averaged over emitter type, the 1/2-inch irrigation intensity had higher total and marketable onion yields than the 1/16- and 1/8-inch intensities. Averaged over emitter type, the 1/2-inch irrigation intensity resulted in the highest super colossal and colossal onion yield. Onions grown with an irrigation intensity of 1/2 inch and drip tape with emitter flow rate of 0.5 L·h–1 produced total yields of 50.0 ton/acre, marketable yields of 48.8 ton/acre, super colossal yield of 1.05 ton/acre, and colossal yield of 13.9 ton/acre. Interactions between irrigation intensities and emitter flow rates were nonsignificant for the number of irrigations, water applied, average soil water potential, or onion yield and grade. There was no significant difference in average soil water potential between treatments. There was no significant difference in total water applied plus precipitation between treatments, with, on average, 32.3 and 31.1 inches applied in 2002 and 2003, respectively. Onion evapotranspiration from emergence to onion lifting totaled 34.6 and 37.3 inches in 2002 and 2003, respectively.
Seven potato cultivars were grown in an adequately irrigated check (100% of crop evapotranspiration replaced at -60 kPa) and three deficit irrigation regimes in order to evaluate varietal response to water stress and to evaluate nitrate leaching below the crop root zone in relation to the irrigation management. Potatoes were grown with sprinkler irrigation on silt loam in 1882 and 1993. Water stress treatments were achieved by partial or complete crop evapotranspiration replacement when soil water potential reached -60 or -80 kPa. In 1992, over all varieties, tuber yield and grade were significantly reduced by the two higher levels of water stress. In 1993, a relatively cool year, yield was reduced by water stress, but grade was not. Tuber internal quality was affected more by variety than by deficit irrigation both years. A comparison of pre-plant and post-harvest soil nitrate and ammonium shows that a small amount of nitrate moved from the top two feet of soil to the third and fourth foot in the check plots. Soil nitrogen accounting for the season showed large surpluses, indicating the importance of natural sources of available nitrogen.
Onions were grown with different soil water potentials as irrigation criteria to determine the soil water potential at which optimum onion yield and quality occurs. Furrow irrigation treatments in 1992 and 1993 consisted of six soil water potential thresholds (-12.5 to -100 kPa). Soil water potential in the first foot of soil was measured by granular matrix sensors (Watermark Model 200SS, Irrometer Co., Riverside, CA) that had been previously calibrated to tensiometers on the same silt loam series. Both years, yield and market grade based on bulb size (more jumbo and colossal onions) increased with wetter treatments. In 1993, a relatively cool year, onion grade peaked at -37.5 kPa due to a significant increase in rot during storage following the wetter treatments. These results suggest the importance of using moisture criteria to schedule irrigations for onions.
Long-day onion (Allium cepa L. `Vision') was subjected to five soil water potential (SWP) treatments (–10, –20, –30, –50, and –70 kPa) using subsurface drip irrigation in 1997 and 1998. Onions were grown on 1.1-m beds with two double rows spaced 0.56 m apart and a drip tape buried 13 cm deep in the bed center. Soil water potential was maintained at the five levels by automated, high-frequency irrigations based on SWP measurements at 0.2-m depth. Onions were evaluated for yield and grade after 70 days of storage. In 1997, total and colossal (bulb diameter ≥102 mm) yield increased with increasing SWP, but marketable yield was highest at a calculated –21 kPa because of greater decomposition in storage in wetter treatments. In 1998 total, marketable, and colossal-grade onion yield increased with increasing SWP. Onion profits were highest with a calculated SWP of –17 kPa in 1997, and at the wettest level tested in 1998. Storage decomposition was not affected by SWP in 1998. Maintenance of SWP at –10 and –20 kPa required, respectively, 912 and 691 mm of water in 1997 and 935 and 589 mm of water in 1998. Onion crop evapotranspiration from emergence to the last irrigation totaled 681 mm in 1997 and 716 mm in 1998.