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Gene E. Lester, John L. Jifon, and Gordon Rogers

Poster Session 22—Postharvest Quality: Cross-commodity 19 July 2005, 12:00–12:45 p.m. Poster Hall–Ballroom E/F

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Guiseppe Colla, Youssef Roupahel, Mariateresa Cardarelli, and Elvira Rea

A greenhouse experiment was carried out to determine growth, yield, fruit quality, gas exchange and mineral composition of watermelon plants (Citrullus Lanatus L. `Tex'), either ungrafted or grafted onto two commercial rootstocks `Macis' [Lagenaria siceraria (Mol.) Standl.] and `Ercole' (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) and cultured in NFT. Plants were supplied with a nutrient solution having an electrical conductivity (EC) of 2.0 or 5.2 dS·m–1. The saline nutrient solution had the same basic composition, plus an additional of 29 mm of NaCl. Increased salinity in the nutrient solution decreased total yield. The reduction in total yield in saline treatments compared to control was due to a reduction in the fruit mean mass and not to the number of fruit per plant. Total fruit yield was 81% higher in grafted than in ungrafted plants. The lowest marketable yield recorded on ungrafted plants was associated with a reduction in both fruit mean mass and the number of fruits per plant in comparison to grafted plants. Salinity improved fruit quality in all grafting combinations by increasing dry matter (DM), glucose, fructose, sucrose, and total soluble solid (TSS) content. Nutritional qualities of grafted watermelons such as fruit DM, glucose, fructose, sucrose, and TSS content were similar in comparison to those of ungrafted plant. In all grafting combinations, negative correlations were recorded between Na+ and Cl in the leaf tissue and net assimilation of CO2 Grafting reduced concentrations of sodium, but not chloride, in leaves. However, the sensitivity to salinity was similar between grafted and ungrafted plants and the higher total yield from grafting plants was mainly due to grafting per se.

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Jin-Sheng Huang and S.S. Snapp

The appearance of a fruit quality defect, shoulder check in fresh-market tomatoes (Lycopersicon esculentum Mill.), has devastated the Michigan industry, and caused sporadic concern elsewhere. The defect appears as a surface roughness that occurs primarily on the shoulder area of the fruit. The fruit appearance is damaged and storability is severely compromised. Microscopic inspection reveals that the surface roughness consists of many microscopic cracks that occur in parallel lines. Our objectives were to describe this defect and evaluate the role of weather conditions and fruit surface moisture in inducing it. Field experiments were conducted in 2001 and 2002 in Southwest Michigan, using the industry standard cultivar Mountain Spring and recommended practices for irrigated, staked fresh market production. The effects of fruit surface wetness and nutrition on quality were evaluated by comparing responses to a plastic rain shelter; Surround WP kaolin spray (to enhance surface wetness); a foliar spray of calcium (Ca at 2 g·L-1), boron (B at 300 mg·L-1), Ca plus B, water alone; and no treatment. A complementary greenhouse experiment investigated the effects of low and high rates of foliar sprays. A very consistent association was found between defect incidence and precipitation events that followed periods of hot, dry weather during rapid fruit expansion. Fruit quality was highest and incidence of defects least in fruit produced under plastic rain covers, with an average marketable yield of 62,270 vs. 44,340 kg·ha-1 for the control. A 28% reduction in defects was consistently associated with Ca + B sprays across harvests and years. In contrast, 18% more fruit had shoulder check defect with kaolin spray, a consistent increase in defect across years compared to control fruit. Greenhouse and field studies gave markedly similar results, except for a water spray control. Incidence of defect was consistently low with the highest rate of B foliar spray.

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Kent D. Kobayashi

Hawaii and Florida practices, sites of the current and future ASHS conferences. The papers cover rootstock and irrigation effects on ‘Gala’ apple mineral nutrition, growth, fruit quality, and yield in Idaho; use of locally produced inputs to improve crop

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E.A. Baldwin

The promise of biotechnology has been slow to be realized, but some commercialized products are finding their way to supermarket shelves. Nevertheless, the future potential remains in the realm of speculation and may be on the verge of delivering some incredible benefits. Since the world population growth is predicted to double in the next 50 years, primarily in developing nations, food resources will become critical. In view of this prediction, we may need every trick in the book to feed the masses, which means either more land (wetlands, forests, and rain forests) will fall to the plow or there will need to be an increase in yields. Concurrently, a decrease in postharvest losses would also be crucial. Various authorities have estimated that 25% to 80% of harvested fruits and vegetables are lost due to damage and spoilage. Early biotech successes were developing plants with enhanced insect resistance (cotton, corn, and potato) and virus resistance (squash and papaya) and improved herbicide tolerance (cotton, soybean, and corn). The only commercialized transgenic fruit engineered for improved postharvest quality so far is the tomato. Future goals for biotechnology include increasing yield, extending shelf life, improving nutritional and flavor quality, and producing specialty proteins or other compounds. Genetically engineered food, however, has met rancorous resistance in Europe, New Zealand, and elsewhere; although, it is somewhat tolerated in the U.S. The U.S., Canada, and Japan lead the world in biotech acreage, with biotechnology accounting for 40% of cotton, 39% of soybeans, and 20% of corn acreage in the U.S. and 73 million acres worldwide.

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Raul I. Cabrera

99 ORAL SESSION 19 (Abstr. 558–564) Floriculture/Foliage: Nutrition/Media Tuesday, 25 July, 2:00–3:45 p.m

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Angela R. Davis, Charles L. Webber III, Wayne W. Fish, Todd C. Wehner, Stephen King, and Penelope Perkins-Veazie

quercitin, this finding is not unexpected and demonstrates the importance of maintaining the other nutritional compounds in fruits and vegetables. Amino acids have well-established individual roles in disease prevention. Arginine, an essential amino acid

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Fredy R. Romero*, Richard J. Gladon, and Henry G. Taber

Impatiens (Impatiens wallerana Hook. f.) is the most important annual bedding plant in the US, based on wholesale dollar volume. Production of high-quality plants requires optimization of the nutrition regimen during growth, especially the total nitrogen (N) concentration and the ratio of N sources. Our objective was to determine the N concentration and ratio of N sources that optimize bedding-plant impatiens growth and development. We used four N concentrations (3.5, 7, 10.5, and 14 mmol·L-1 of N) in factorial combination with four ratios of nitrate-N (NO3 --N) to ammonium-N (NH4 +-N) (4:0, 3:1, 1:1, and 1:3). Application of treatments began at day 30, and every-other-day applications were conducted until day 60. From day 60 to day 70 only deionized water was applied. N concentration and source displayed interation for most growth parameters. When N was supplied at a concentration ≤7 mmol·L-1, the NO3 --N to NH4 +-N ratio did not affect growth. When N was supplied at a concentration ≥10.5 mmol·L-1, a 1:3 NO3 --N to NH4 +-N ratio yielded the greatest shoot dry weight, shoot fresh weight, plant diameter, and number of flower buds per plant. With a NO3 --N to NH4 +-N ratio of 4:0, these growth parameters decreased. To produce high-quality, bedding-plant impatiens, N should be applied at NO3 --N to NH4 +-N ratios between 1:1 and 1:3 in combination with an N concentration of 10.5 mmol·L<-1 at each fertigation from day 30 to day 60 of the production cycle.

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Carolyn F. Scagel

Using several different ericaceous ornamental species, we compared the growth, mineral nutrition, and composition of plants in response to growing media amended with varying proportions of sphagnum moss peat (peat) or coir dust (coir). Plants were grown for 16 weeks in media consisting of 80% composted Douglas fir bark with 20% peat, 20% coir, or 10% peat and 10% coir. Sixteen weeks after planting, decreases in extractable P were larger in peat-amended medium than the coir-amended medium, while decreases in extractable NH4-N and NO3-N were larger in the coir-amended medium. In general, leaf and stem dry weight, the number of leaves and stems, and total stem length increased with increasing proportion of coir in the medium while root dry weight either increased (Kalmia latifolia), decreased (Rhododendron, Gaultheria), or was not influenced by increasing the proportion of coir in the medium. The composition of the growing medium also influenced aspects of plant marketability and quality including: leaf greenness (SPAD), plant form (e.g., number of leaves per length of stem), and partitioning of biomass (e.g., root to shoot ratio). Nutrient uptake and fertilizer use was significantly different between the media types. Depending on the cultivar, we found that the coir-amended medium resulted in higher uptake or availability of several nutrients than peat-amended medium. Up take or availability of N, P, K, Ca, and S was enhanced for several cultivars, while uptake or availability of Mg, Fe, and B was similar between media types. Most cultivars/species growing in the coir-amended medium had higher production or accumulation of proteins and amino acids in stems than plants growing in peat-amended medium, while the production of proteins and amino acids in roots was lower in plants growing in coir-amended than in peat-amended medium. For the cultivars/species we tested, coir is a suitable media amendment for growing ericaceous plants and may have beneficial effects on plant quality.

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Thomas A. Obreza and Robert E. Rouse

Controlled-release N (CRN) fertilizer is receiving interest as a possible nutrient best management practice (BMP) for Florida citrus production, but grower acceptance will be limited until cost decreases and familiarity with CRN materials increases. The objective of this study was to compare long-term citrus production resulting from N fertilizer programs containing isobutylidene diurea (IBDU) or methylene urea (MU) with a conventional water-soluble N fertilizer program to determine the magnitude of horticultural utility provided by CRN. We applied N to a newly planted `Hamlin' orange (Citrus sinensis L. Osbeck) orchard using three sources (100% ammonium nitrate (AN); a 50/50 mixture of AN/IBDU; a 60/40 mixture of AN/MU) at four rates (0.25, 0.5, 1.0, and 2.0 or 1.5 times the recommended annual rate) in factorial combination, and continued for 7 years. During this period, AN was applied 31 times vs. about 15 times for CRN-containing fertilizers. We measured fruit yield, juice quality, and total soluble solids (TSS) yield in years 4 through 7 and found that they generally were not affected by N source, especially when year-to-year variation was taken into account. In year 7, fruit and TSS yields of well-fertilized trees reached 153 and 9.2 kg/tree, respectively. Maximum 4-year cumulative fruit and TSS yields (486 and 27.6 kg/tree, respectively) occurred at an N rate of 200 kg/ha. Maximum juice quality occurred at 180 kg N/ha. We feel the CRN materials tested could be used successfully in a nutritional BMP program that would maintain high yields while potentially decreasing N loss to the environment.