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J.R. Davenport, C.A. Redulla, M.J. Hattendorf, R.G. Evans, and R.A. Boydston

An accurate yield map is imperative for successful precision farming. For 3 years (1998 to 2000) two to four potato (Solanum tuberosum) fields on a commercial farm in southeastern Washington were yield-monitored using commercial yield monitoring equipment without operator interaction. Multiple potato diggers were used to harvest the fields and diggers used were not necessarily the same at each harvest. In all years, yield monitoring data were missing due to equipment failure or lack of yield monitoring equipment on all diggers. Banding, due to dissimilar calibrations, different equipment used, or differential digger performance was observed in 1998 and 2000. Based on experience described here, some yield monitor data need minimal postprocessing or correction, other data need substantial postprocessing to make them usable, and other data may not be reliable due to equipment failure, improper calibration, or other causes. Even with preharvest calibration, it is still likely that the potato yield monitor data will need differential postprocessing, indicating that yield maps lack accuracy. In addition, comparison to yield data collected at multiple points within the field, this study found that the yield monitor over estimated potato yield. Thus, with some postprocessing, a useful yield map showing within field differences is possible. However, without significant postprocessing, the practice of using multiple diggers and yield monitors for potato harvest, both within and between fields, severely limits the ability to make consistent yield maps in commercial potato operations.

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Barbara J. Daniels-Lake and Robert K. Prange

The importance of light fry color to the potato ( Solanum tuberosum L.) processing industry cannot be overstated. Because most of the North American potato crop must be stored for many months between harvest and processing, it is important to

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Petra Wolters, Wanda Collins, and J.W. Moyer

The establishment of a sweet potato repository in Georgia that will eventually accept and distribute true seed of sweet potato [Ipomoea batatas (L.) Lam.] raised the question of seed transmission of viruses, especially of sweet potato feathery mottle virus (SPFMV). Seedlings obtained from virus-infected parent plants were free of viral infection. Examination of virus distribution in virus-infected plants determined that SPFMV was present in vegetative tissue, but not in reproductive organs, indicating that the probability of SPFMV transmission in sweet potato through seed is very low.

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J.D. Abbott and L. T. Thetford

Cyromazine is a triazine molecule with insect growth regulator properties being developed for control of Colorado potato beetle (Leptinotarsa decemlineata Say) (CPB) in vegetables. Research presented focuses primarily on results with potato (Solanum tuberosum L.), however, crop safety has been observed in other crops within the Solanaceae. Several trials were conducted in PA and NY during 1991 to examine the rates and timing necessary to control CPB in potatoes. Data from replicated small plot trials and non-replicated large block trials are included. Rates examined ranged 70 to 560 g ai na-1 applied alone or in combination with a pyrethroid or Bt. Comparisons were made with insecticides presently registered for CPB control in potatoes and cyromazine compared quite favorably. Two applications per CPB generation were made, the first at the beginning of CPB egg hatch and a second 7-16 days later for each generation. This application schedule provided excellent (90%) control of CPB larvae. The reduction in larvae also resulted in a reduction in adult CPB and potato leaf area damaged through insect feeding. In the test conducted in PA, an increase in size and number of tubers was observed when plants were treated with cyromazine. -These increases resulted in a 23-28% increase in total yield compared to that obtained from the untreated check plots.

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M. Moriondo, M. Bindi, and T. Sinclair

Crop growth simulation models have been mainly developed to simulate final yield reliably. Thus, a main challenge in these models is the definition of a stable method for expressing the growth of harvested organs (e.g., fruit, seed, tuber, etc.). Generally, two approaches have been used: growth rate analysis of harvested organs [yield growth rate (YGR)] and analysis of harvest index (HI) increase over time (dHI/dt). This work aims to: 1) examine whether YGR and dHI/dt increase linearly over much of growing period, and 2) compare the two growth indices in terms of stability across a number of treatments, in order to identify which is the best indicator of harvest-organ growth. This analysis has already been performed for a large number of field crops, including wheat (Triticum aestivum L.), sunflower (Helianthus annuus L.), soybean [Glycine max L. (Merr.)], and pea (Pisum sativum L.), but it has never been attempted in crops where final yield is not simply seeds. In this study, YGR and dHI/dt performances for tomato (Lycopersicum esculentum Mill.), potato (Solanum tuberosum L.), and eggplant (Solanum melongena L.) were compared using 21, 18, and 4 datasets, respectively. Results indicated that both descriptors of harvest-organ growth increased linearly for most of the growth period, whilst the comparison among the two variables in terms of stability showed that, although a direct statistical test failed, dHI/dt was more suitable to describe harvest-organ growth (smaller coefficient of variability) under a large range of crop management conditions (e.g., irrigation, sowing date, planting density, and water salt concentration).

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Daniel Keifenheim and Cindy Tong*

Anthocyanins are a class of flavonoids that are responsible for pigments in flowers, fruit, and potato periderm. Developing `Norland' potatoes synthesize anthocyanins in periderm tissue when the tubers are mere swollen stolon tips. As the tubers enlarge, anthocyanin accumulation seems to stop, and anthocyanins synthesized early in development seem to be diluted as the tubers enlarge. Expression of dihydroflavonol reductase (DFR) limits anthocyanin synthesis in grape and maize fruit, and in petunia and snapdragon flowers. However, DFR expression in periderm tissue occurred throughout tuber development (Hung et al., 1999). To determine if expression of late anthocyanin pathway genes limit anthocyanin synthesis in developing potato tubers, we performed RNA gel blot analyses. Expression of leucoanthocyanidin dioxygenase and UDP glucose: flavonoid 3-O-glucosyl transferase was observed in swollen stolon tips but not in periderm of later tuber development stages. Surprisingly, expression was also observed in cortex tissue, although that tissue remained white throughout tuber growth.

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Mildred N. Makani, Steven A. Sargent, Lincoln Zotarelli, Donald J. Huber, and Charles A. Sims

Potato ( Solanum tuberosum L.) tubers continue active metabolism after harvest and require appropriate storage conditions to minimize losses that can arise from these physiological processes ( Kumar et al., 2004 ). One key factor determining

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David R. Duncan, David Hammond, Jim Zalewski, John Cudnohufsky, Wojciech Kaniewski, Mike Thornton, Jeffrey T. Bookout, Paul Lavrik, Glennon J. Rogan, and Jennifer Feldman-Riebe

After more than 10 years of research, Monsanto scientists have developed improved seed potatoes that are protected from serious pests, including insects and disease. The first commercial products resulting from this effort were NewLeaf ® potatoes derived from `Russet Burbank' and `Atlantic' parents. The NewLeaf® product was commercialized in 1995 and contains a gene from Bacillus thuringiensis (variety tenebrionis) (B.t.t.). for the production of the Cry3A protein. Potatoes expressing this gene are completely protected from the Colorado potato beetle (CPB) and need no additional chemical protection for this insect pest. The U.S. Food and Drug Administration (FDA), U.S. Dept. of Agriculture (USDA), and U.S. Environmental Protection Agency (EPA) have all determined that these potatoes are the same in safety and nutritional composition as any other `Russet Burbank' and `Atlantic' potatoes. These potatoes have also been approved by Health Canada, Agri-Food Canada and Agriculture Canada and by Japan and Mexico for food use. Commercial growers across North America have experienced outstanding performance while growing NewLeaf® potatoes 3 years in a row. This level of performance is the result of stable, nonsignificant differences in expression of the Cry3A gene. The stable performance, also, is a result of an effective insect resistance management program based on maintaining CPB refuges near NewLeaf ® fields, reducing CPB populations, and monitoring for CPB surviving exposure to NewLeaf® potatoes. In 1998 NewLeaf Y®), conferring resistance to both CPB and potato virus Y, and NewLeaf Plus®, conferring resistance to CPB and potato leafroll virus will be commercially released.

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D.S. Douches, T.J. Kisha, J.J. Coombs, W. Li, W.L. Pett, and E.J. Grafius

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most serious insect pest of potatoes throughout the eastern and north central United States. Host plant resistance to the Colorado potato beetle has been identified in wild Solanum species and Bt-transgenic potato lines. Detached-leaf bioassays (72 h) were conducted on insecticide-resistant, first instar Colorado potato beetles to study the effectiveness of individual and combined host plant resistance traits in potato. Potato lines tested include non-transgenic cultivars (`Russet Burbank', `Lemhi Russet', and `Spunta'), a line with glandular trichomes (NYL235-4), a line with high foliar leptines (USDA8380-1), and transgenic lines expressing either codon-modified Bt-cry3A or Bt-cry5 (Bt-cry1Ia1). Bt-cry3A transgenic lines, foliar leptine line, and foliar leptine lines with Bt-cry5 had reduced feeding compared to non-transgenic cultivars. Glandular trichome lines and glandular trichome lines with Bt-cry5 did not reduce feeding in this no-choice feeding study. Some Bt-cry5 transgenic lines, using either the constitutive promoters CaMV35s or (ocs)3mas (Gelvin super promoter), were moderately effective in reducing larval feeding. Feeding on Bt-cry5 transgenic lines with the tuber-specific patatin promoter was not significantly different than or greater than feeding on the susceptible cultivars. Mortality of first instars was highest when fed on the Bt-cry3A lines (68% to 70%) and intermediate (38%) on the Bt-cry5 `Spunta' line SPG3 where the gus reporter gene was not included in the gene construct. Host plant resistance from foliar leptines is a candidate mechanism to pyramid with either Bt-cry3A or Bt-cry5 expression in potato foliage against Colorado potato beetle. Without multiple sources of host plant resistance, long-term sustainability is questionable for a highly adaptable insect like the Colorado potato beetle.

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Xiaohong Wang, Bishun Ye, Xiangpeng Kang, Ting Zhou, and Tongfei Lai

validated by PCR amplification using a pair of PVX sequencing primers and electrophoresis analysis on a 1% agarose gel ( Fig. 1C ). Fig. 1. ( A ) Developmental expression of LeHB-1 in tomato cultivar Ailsa Craig and ( B–D ) construction of potato virus X