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Luz Marina Reyes and Wanda W. Collins

Genetic control of seven enzymes in Ipomoea trifida (H.B.K.) G. Don. (diploid, tetraploid, and hexaploid populations) and I. batatas (L.) Lam. was studied by starch gel electrophoresis. Inter- and intraspecific polymorphisms were detected for all enzymes in the populations analyzed, except catalase (CAT, EC 1.11.1.6). Phosphoglucomutase (PGM; EC 2.7.5.1), phosphoglucose isomerase (PGI; EC 5.3.1.9), glutamate oxaloacetate transaminase (GOT; EC 2.6.1.1), menadione reductase (MNR; EC 1.6.99.2), shikimate dehydrogenase (SAD; EC 1.1.1.25), and malate dehydrogenase (MDH; EC 1.1.1.37) collectively were encoded by a minimum of 13 genetic loci resulting in 24 allozymes. Results from the diploid I. trifida were used to infer the genetic basis of these enzymes in the polyploid species. All polyploid populations shared almost the same number of allozymes with diploid I. trifida. PGM and PGI showed evidence of duplicated genes in the polyploid series. A unique allele for MNR was detected only in polyploid series.

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Douglas C. Sanders and Luz M. Reyes

Two formulations of a new methylene urea product on tomato were evaluated. Applications of 150, 200, 250 lb/acre of N in eastern North Carolina and 175 and 250 lb/acre of N in western North Carolina of both liquid and dry formulation of the material were made. The liquid was applied the first 6 weeks of growth and the dry applied at planting. These treatments were compared with 200 lb/acre of N (standard) and 300 lb/acre of N, which were fertigated throughout the season. In eastern North Carolina, all rates of the liquid and high rate of dry formulations produced more yield of larger fruit than the standard. In western North Carolina, all methylene urea sources out-performed the standard. Soil and foliar nitrate was somewhat greater than the standard throughout the season, but, at end of season in the west, only the 250 dry material had more N in the soil. Methylene urea treatments took up more N than the control. All methylene urea except 200 dry produced more dollars per acre than the standard.

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Luz M. Reyes, Orlando Martinez, and Nubia Martinez

Variability of `chococito' maize cultivars (Zea mays L.), have been decreased in the Anchicaya river area, because new crops were established there. Process of recuperation, promotion, and conservation under in situ and ex situ conditions were proposed to the community of the area. Using participatory research methodologies, memory and uses were recuperated for four varieties through the Exchange Seed Interchange Fund (ESIF), established just for maize. The study was carried out in two components: social and agronomic. The social component was development in three phases: i) diagnosis; ii) establishment of the ESIF, and iii) socialization. The agronomic characterization was performed with members of the community through the development of the crop. Twenty-six variables, both quantitative and qualitative, were registered. The cultivars were appropriated for extreme conditions of the Anchicaya river area, high temperatures (30 °C) and high level of precipitation (6000 mm/year). During the process of cropping, it was found that the “to cut and to decay” system is the most common used in this region. Using multivariate analyses of quantitative and qualitative variables, the relationships between materials of `Chococito” race were found. The dendograms for these cultivars had shown differences among them. As a complement of the in situ conservation done by compromise of the Anchicaya's community, a duplicate under ex situ conditions was established at the Genetic Resources Laboratory, belonged to the Agronomy Dept. of National Univ. of Colombia.

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Luz Marina Reyes, Orlando Martinez, and Margarita Beltran

Fifteen clones of banana and plantain of different ploidies, belonging to the Colombian Collection of Musaceas (CCM), maintained at in vitro conditions were characterized. Twenty-three isozyme systems were analyzed using young leaves of micropropagated clones. Eleven systems presented electrophoretic activity: diaphorase (DIA), esterase (EST), glutamate dehydrogenase (GDH), malate dehydrogenase (MDH), malic enzyme (ME), peroxidase (PRX), phosphoglucoisomerase (PGI), phosphogluconate dehydrogenase (PGDH), phosphoglucomutase (PGM), ribulose biphosphate carboxilase (RUB), and shikimate dehydrogenase (SKDH). DIA and RUB isozymes are reported the first time for the genus Musa, and ME, GDH, PGDH, and PGI are not reported previously in acrilamide support. A total of 24 loci were identified that encoded at least 50 alleles. The enzymes with greater genetic variability were EST and DIA, with 14 and 10 alleles, respectively—these represent 48% of the polymorphism detected in this study. The systems PGM, SKDH, PGDH, and ME allowed to differentiate clones of M. acuminata (bananas AA and AAA) from hybrid clones derived of M. acuminata × M. balbisiana (plantains AAB and ABB). Otherwise, it was found that materials maintained under in vitro conditions for more than 10 subcultures presented evidence of variation at the protein level. The isozymes that allowed us to observe these changes were: DIA, EST, ME, PGDH, PGM, and SKDH.

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Luz M. Reyes, Douglas C. Sanders, and Wayne G. Buhler

This study was conducted to compare different formulations of a slow-release fertilizer with a conventional fertilizer program to determine their impact on yield and growth of bell pepper (Capsicum annuum). Two formulations of a methylene-urea slow-release fertilizer (Nitamin®) were evaluated on drip-fertigated and plastic-mulched bell peppers during 2006 in the eastern coastal plain and western Appalachian mountains of North Carolina. Liquid slow-release formulations were applied the first 6 or 9 weeks of the growing season and a dry formulation was banded at planting. Treatments were compared with the extension-recommended rate of 200 lb/acre nitrogen (N) (NC-200) and a high-input fertilizer rate of 300 lb/acre N (HI-300) from calcium nitrate injected in 12 weekly applications of drip irrigation. Irrigation was applied twice per week. The slow-release granular formulation at 200 lb/acre N produced the highest marketable yield and better canopy quality in eastern soil. Early marketable yield for this treatment accounted for 46% of the total yield. All slow-release treatments had higher N use efficiency (NUE) values than NC-200 and HI-300 in the eastern study. In loam soil (western study), pepper yield was statistically similar among treatments. Lower rates (150 lb/acre N) of slow-release fertilizer performed as well as NC-200 and HI-300 for marketable yield. Low rates (150 lb/acre N) of one of the liquid formulations performed better in total and marketable NUE than NC-200 and HI-300 in Fletcher, North Carolina. Liquid and dry formulations of slow-release fertilizer showed a potential to be used on bell pepper production across the state at reduced N rates, with greater impact on yield in coarse-textured soils found predominantly in the eastern coastal plain region.

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Douglas C. Sanders, Dennis J. Osborne, and Luz Reyes

Land-grant institutions throughout the US face declining resources in general. Particularly reduced is institutional ability to offer core graduate and upper level undergraduate courses in production agriculture and agricultural science. For example, while North Carolina (NC) State University is still able to offer a wide range of upper-division production courses in Horticulture, many sister institutions are facing restrictions on offerings in Fruit and Vegetable Production and Floriculture courses. New areas such as Sustainable Agriculture and Organic Farming also justify course offerings but few resources exist to create and teach such courses. At NC State, distance education (DE) is able to begin overcoming these problems in several ways. First, high demand, low-seat-available classes such as Postharvest Physiology can offer additional enrollment for credit if open to DE students. Second, courses offered asynchronously or with alternative delivery strategies (such as the videotapes distributed in this course) students having course/time conflicts in a semester can enroll simultaneously in two campus time-conflicted courses, completing both successfully. The framework for the Postharvest course now being taught via DE and how it came to gain institutional support will be discussed in this paper.

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Marjorie Reyes-Diaz, Miren Alberdi, and Maria de la Luz Mora

Aluminum (Al) toxicity is a major agronomic problem in acid soils. Most studies regarding Al stress focus on phenomena occurring in the roots; however, less is known about the effects of Al stress on photosynthetic apparatus functionality. Our aim was to rank three highbush blueberry (Vaccinium corymbosum) cultivars according to their tolerance to acid and Al stresses. Additionally, the levels of Al toxicity for highbush blueberry were established. ‘Brigitta’, ‘Legacy’, and ‘Bluegold’ were grown in a greenhouse in hydroponic solutions containing different Al concentrations (0, 25, 50, 75, and 100 μm) for 0 to 48 h and were allowed to recover (without Al) over 24 h. In all Al-treated cultivars, root growth inhibition was found at the highest Al treatment. However, ‘Brigitta’ also showed root growth up to 75 μm Al. Photochemical parameters decreased substantially due to Al treatments in ‘Bluegold’ (up to 98% inhibition) and ‘Legacy’ (up to 80% inhibition) without total recovery. In contrast, ‘Brigitta’ showed a better photosystem II performance and root growth than the other cultivars. These results suggest that ‘Brigitta’ is the best cultivar for use in acid soils with Al toxicity, followed by ‘Legacy’. ‘Bluegold’ was highly sensitive to Al stress. In addition, Al toxicity levels for blueberries depend on the genotype studied.

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Luz M. Reyes, Dennis Osborne, Donn R. Ward, and Douglas C. Sanders*

One key to protecting the nation's food supply is training packinghouse and field workers in food safety principles. Southern producer/packers are typically grower/packers. Such producers usually are seasonal, have their own packinghouse operation and are small scale. They use migrant and seasonal labor. Also worker training, sanitary practice and facilities are either somewhat limited or completely lacking in such operations. Further, the use of seasonal and migrant labor dictates the use of Spanish language interpreters for training. These trainers are in marked shortage. To help meet this need for trainers and training materials we developed a bi-lingual (Spanish/English) “flip chart” GAPs training aid. It contains 48 charts explaining food safety principles to be considered in the field and in the packing operation. These educational materials can be used by small farmers, growers and packers for training sessions. Such material is particularly useful in preparing for third-party audits.

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Doug Sanders, Luz M. Reyes, David Monks, Frank Louws, and James Driver

We evaluated the influence of three compost sources and compost amended with T382 with fumigant Telone C-35 and various combinations of compost and Telone C-35 on the yield and pest management of cucumber, pepper, tomato, collard, southern pea, and summer squash in a multicrop rotational system. In the first year, there were few differences between the compost treatments and Telone C-35, but all treatments resulted in more yield than the control. In the second year, all compost treatments and/or Telone C-35 improved total and marketable yield of cucumber, pepper, tomato, southern pea, and summer squash. Furthermore, in the second year, Telone C-35 treat-ments produced more yield than some of the compost treatments in tomatoes. Combining Telone C-35 with compost did not differ from either treatment alone. Nematode and disease assessments were not consistent and will be discussed in further detail.

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Luz Reyes*, Sylvia M. Blankenship*, Jonathan R. Schultheis*, and Michael D. Boyette

Sweetpotato roots, especially the cultivar Beauregard, tend to experience epidermal loss during harvest and postharvest handling which results in a less attractive product in the market. A survey study was conducted among North Carolina (N.C.) sweetpotato growers in Fall 2001 and 2002. The purpose of the survey was to gather information and try to correlate cultural practices, growing conditions and site characteristics with the occurrence of attractive roots and to define new scientific approaches to reducing epidermal loss. Samples were obtained from 42 N.C. farms. Survey field information and laboratory results were correlated to identify possible factors affecting the appearance of the roots. 1300 roots were used to measure skin adhesion, peeling susceptibility, skin moisture, skin anthocyanin and lignin content. From survey questions, 50 characteristics were defined for each sample, according to field characteristics, cultivar information, cultural practices and harvest and postharvest practices. Statistical analyses were performed to determine the relationship between the skin characteristics analyzed at the laboratory, and the survey descriptors information. Analysis of variance was used for laboratory data analysis. Person correlations were made between survey variables and laboratory characteristics. Several possible relationships between root appearance and other characteristics/practices were identified. Root skin adhesion may improve in later generations from elite propagation material. Early application of phosphate and potash fertilizers were correlated to improved root skin adhesion. There appeared to be a relationship between soil moisture at harvest time, increased lignin content in the skin and peeling susceptibility. Future areas of study were identified.