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  • Author or Editor: Carl E. Motsenbocker x
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Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.

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Cayenne pepper fruit adhere tightly to the calyx/receptacle, increasing the cost of hand harvest and restricting mechanical harvest. Eight (8) cayenne pepper genotypes were selected from field observations to characterize fruit detachment forces(FDFs) and examine potential relationships between FDF and other fruit parameters. A preliminary greenhouse experiment revealed two genotypes with consistently lower FDFs and two with consistently higher FDFs over several progressive harvest. A field experiment confirmed these characteristics. No correlation between any fruit parameter and FDF was found to be consistent over the genotypes studied.

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Two genotypes of cayenne pepper, Capsicum annuun, have been previously identified which differ significantly in ease of fruit detachment force. Both greenhouse- and field-grown plants of these genotypes, Cajun1-9027 and Cap-9004, were investigated for differences in cell type or organization where the fruit and receptacle join. Scanning electron microscopy revealed that mature fruit of genotype Cajun1-9027, which does not separate, exhibits a distinct region of sclerified cells that extend from the periphery of the fruit into the receptacle for at least 15 cell layers. In contrast, mature fruit of the more readily detachable genotype, Cap-9004, had fewer sclerified cells at the point of detachment. Neither genotype exhibits a well-defined abscission zone prior to, or at, maturity. Interpretation of histochemical staining of fruit-receptacle sections following ethylene treatment at different fruit developmental stages will be discussed.

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Field experiments were conducted to assess how sweetpotato [Ipomoea batatas (L.) Lam.] clones interfere with weeds and how clones tolerate weed interference. Eleven clones with architecturally different canopies were evaluated for yield, canopy surface area and dry mass, weed dry mass, and light interception at ground level. A 2-fold difference in ground area covered by canopy surface area was observed among the eleven clones 42 days after planting, and a 3-fold difference in canopy dry mass at harvest. Yields were reduced from 14% to 68% by weed interference. The yields of high-yielding clones, `Beauregard', `Excel', L87-125, `Regal', `Centennial', and W-274, were reduced to a significantly greater extent by weeds than were yields of the other five clones. No differences were observed between clones for weed suppression as measured by weed dry mass at harvest and ground light interception. Short-internode and long-internode clones had similar competitive abilities. Yield of high-yielding clones was impacted more by weed interference than was that of low-yielding clones.

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This is a horticulture case study of the export market for melons (Cucumis melo) from Central America to the United States. Melons have provided growers an excellent production and marketing opportunity since the early 1980s. “Off-season” shipments have changed from a consumer novelty to a commodity. The case documents how this producer entered the industry and became a dominant firm using a cost leadership strategy that included adopting advanced production technology and generating large sales volume to take advantage of its opportunity. As the product moved through the cycle from new product to mature market, there were changes in behavior by competing firms, a slowdown in growth of the markets, and reduced profits. Other management practices such as creating profit centers, using employee incentives at all levels, and outsourcing transportation and brokerage services were used to supplement the cost leader strategy. The development of the market and of the firm is documented, providing the basis for discussion of management and marketing issues in courses at the university level in horticulture and agribusiness.

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Of eight genotypes of cayenne pepper (Capsicum annuum L.) examined, two were identified that differ significantly in ease of fruit detachment force. Greenhouse and field-grown plants of these genotypes, Cajun 1-9027 and Cap-9004, were investigated for differences in cell type and organization at the fruit and receptacle junction. Scanning electron microscopy revealed that mature Cajun 1-9027 fruit that did not separate exhibited a distinct region of sclerified cells that extended from the periphery of the fruit into the receptacle for 25 to 30 cell layers. In contrast, mature fruit of the more readily detachable Cap-9004 had 10 to 15 layers of sclerified cells at the region of detachment. Histochemical and stereological techniques indicated that Cajun 1-9027 had a greater volume of sclereids than Cap-9004. Cajun 1-9027 exhibited smaller cortical cells in the detachment region than Cap-9004. Neither genotype exhibited a well-defined abscission zone at maturity in the detachment region. The presence of more sclerified cells and increased lignification in Cajun 1-9027 compared to Cap-9004 probably contributed to the differences in ease of detachment between the two genotypes.

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Field studies were conducted in 1991 with `Jalapeno-M' and `TAM' Jalapeno pepper. Plants were established by direct seeding at 10, 20, 30, and 40 cm in-row plant spacing. Lodged plants, fruit quality and yield were monitored. A commercial snap-bean harvester was evaluated for harvest. Closer plant spacings resulted in greater yields and reduced plant lodging. No interaction of variety with plant spacing was observed. There were, however, differences in several yield parameters due to variety. Fruit quality characteristics of mechanically and hand harvested pepper stored at 6 C were similar. The use of the mechanical snap-bean harvester appears to be a feasible technique to harvest Jalapeno pepper.

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Field studies were conducted in 1991 and 1992 to evaluate the effect of in-row spacing on machine-harvested jalapeno pepper (Capsicum annuum L.) yield and plant characteristics. In 1991, `TAM Mild Jalapeno-1' (TAMJ1) and `Jalapeno-M' (JM) were planted at 4-, 8-, 12-, and 16-inch (10-, 20-, 30-, 40-cm) in-row spacings and, in 1992, TAMJ1 was planted at 3-, 6-, 9-, and 12-inch (7.5-, 15-, 22.5-, 30-cm) spacings. Total marketable yield increased linearly for JM (in 1991), while the yield response was quadratic for TAMJ1 in 1992 with narrower in-row spacing. Total marketable yield for JM (1991) and TAMJ1 (1992) was highest for the narrowest spacing, 4 and 3 inches, respectively. Red fruit yield of both cultivars in 1991 increased linearly with narrower spacing. In 1992 there were no differences in red fruit yield among in-row spacings. Plants lodged more at wider spacings. In-row spacings as narrow as 4 inches may increase marketable yield of machine-harvested jalapeno pepper.

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Forty-five cultivars of lettuce (Lactuca sativa) were field-grown using best management practices at the Louisiana State University Agricultural Center (LSU AgCenter) Botanic Gardens in Baton Rouge during the Fall 2011 and Fall 2012 seasons. Recommended cultivars were selected for commercial production in Louisiana based on fresh weight and lettuce size (width and height). Nitrate (NO3 ) concentration was analyzed for each cultivar, as lettuces are known to accumulate and concentrate NO3 , and were then compared with the U.S. Environmental Protection Agency’s (EPA) oral reference dose (RfD—the EPA’s maximum acceptable oral dose of a toxic substance) of 1.6 mg NO3-nitrogen (N) per kilogram body weight per day. Recommended butterhead cultivars were Caliente and Harmony (21.6 and 13.9 ppm NO3 , respectively); recommended green-leaf cultivars were Salad Bowl and Tango (10.6 and 4.6 ppm NO3 , respectively); recommended red-leaf cultivars were Red Salad Bowl, Red Sails, and New Red Fire (15.2, 15.4, and 24.0 ppm NO3 , respectively). The only recommended romaine cultivar was Green Towers (11.2 ppm NO3 ), and recommended crisphead cultivars included Raider and Ithaca (17.6 and 14.9 ppm NO3 , respectively). Of the highest yielding cultivars, New Red Fire accumulated the greatest NO3 concentration: 24.0 ppm in both years 1 and 2. The NO3 concentration is less than the levels of concern for both men and women 20 to 74 years old, 3.9% of the RfD for men and 4.59% of the RfD for women.

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