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R. Gil Ortega, M. Gutierrez and J. Cavero

Pimiento pepper (Capsicum annuum var. annuum L. `Piquillo') was directly seeded on raised beds in double rows 0.35 cm apart. Plants were thinned within the row to establish densities ranging from 13,333 to 186,667 plants/ha. Marketable yield of pepper increased as plant density increased to 100,000 plants/ha. However, with plant densities >100,000 plants/ha, marketable yield did not increase (2001) or slightly decreased (2000). Plant density affected pepper yield only in the first harvest date. Fruit number and fruit weight per plant decreased with increasing plant populations. Weight per fruit decreased slightly at densities >100,000 plants/ha. The increase in yield per hectare as plant density increased was mainly a result of increased number of fruit per hectare. The intercepted PAR by the pepper canopy increased with increases in plant density to about 100,000 plants/ha and this increased interception of PAR resulted in an increase in yield. Plant densities in the range of 100,000 to 120,000 plants/ha were optimal in terms of marketable yield.

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J. Cavero, R. Gil Ortega and M. Gutierrez

Paprika pepper (Capsicum annuum var. annuum L., `Agridulce SIA') was direct-seeded on raised beds in double rows 0.35 cm apart. Plants were thinned within the row to establish densities ranging from 13,333 to >500,000 plants/ha. Yield of paprika pepper increased as plant density increased, but plant densities >200,000 plants/ha resulted in only small increases in yield. Fruit number and dry fruit weight/plant decreased with increasing plant populations, and weight/fruit decreased slightly. The increase in yield/ha as plant density increased was a result of increased numbers of fruits/ha. Pigment content (ASTA units) declined linearly as plant density increased, whereas moisture content of red fruits at harvest remained unaffected. Plant densities in the range of 150,000 to 200,000 plants/ha were optimal in terms of fruit yield and pigment content.

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L. Pascual, F. Perfectti, M. Gutierrez and A.M. Vargas

Isozymes have been used as genetic markers to characterize seven Spanish cherimoya (Annona cherimola Mill.) cultivars. Fifteen enzyme systems were analyzed. Ten varied [aconitase (ACO, EC 4.2.1.3), alcohol dehydrogenase (ADH, EC 1.1.1.1), glutamate oxalacetate transaminase (GOT, EC 2.6.1.1), isocitrate dehydrogenase (IDH, EC 1.1.1.42), leucine aminopeptidase (LAP, EC 3.4.11.1), malate dehydrogenase (MDH, EC 1.1.1.37), phosphoglucose isomerase (PGI, EC 5.3.1.9), phosphoghtcomutase (PGM, EC 2.7.5.1), shikimate dehydrogenase (SKDH, EC 1.1.1.25), and triose phosphate isomerase (TPI, EC 5.3.1.1)] and five did not [acid phosphatase (ACPH, EC 3.1.3.2), diaphorase (DIA, EC 1.6.4.3), malic enzyme (ME, EC 1.1.1.40), 6-phosphogluconic dehydrogenase (6PGDH, EC 1.1.1.44), and superoxide dismutase (SOD, EC 1.15.1.1)]. Two cultivars, Campa and Campa Mejorada, had identical banding patterns for all enzymes tested. All others were identified as distinct cultivars because of isozyme differences. The identical isozyme profiles of `Campa' and `Campa Mejorada' probably indicate that they are the same cultivar. A cluster analysis of isozyme profiles showed that Spanish cultivars were clearly different from Californian cultivars.

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Marìa Andrade-Rodrìguez, Angel Villegas-Monter and M. Alejandra Gutièrrez-Espinosa

Polyembryony is an important characteristic for citrus that allows them to be propagated clonally through seed. Even when it is genetically controlled by a quantitative trait, the environment in which the seed is developed can affect it. The aims of this investigation were to evaluate polyembriony in two citric rootstocks in two harvest cycles and embryo germination of polyembrionic seeds. Embryos of 300 seeds of Citrus volkameriana and C. amblycarpa were counted and measured in Summer-Fall and Winter 1998 and 1999, respectively; embryo of 50 seeds of both rootstocks were germinated in vitro. The number of embryos per seed was 1.9 and 1.6 in C. volkameriana and 4.7 and 5.7 in C. amblycarpa. In C. volkameriana, we observed 42% of monoembryonic seeds during summer-fall and 67% in winter, whereas in C. amblycarpa 5.0 and 4.1% were detected, respectively. Only embryos that were larger than 1 mm long germinated. Even when germination takes similar time (5 to 6 days), further growth is faster in larger embryos (5 to 10 mm) than smaller ones. Therefore, size of embryos would need to be considered for propagation purposes.

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J.J. Mangas, E. Dapena, M.S. Rodriguez, J. Moreno, M.D. Gutiérrez and D. Blanco

Water-soluble pectin (WSP), chelator-soluble pectin (CSP), and hydrochloric acid-soluble pectin (HASP) were monitored in five Asturian apples (Malus domestics Borkh.) throughout ripening. The alcohol-insoluble solid content was found to decrease during ripening, while those of the WSP and CSP fractions increased in the final stages of ripening. This increase was probably at the expense of the HASP content, which had decreased by the end of the ripening period.

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R. Lezama-Gutierrez, J. Molina-Ochoa, O. Rebolledo-Dominguez, M. Gonzalez Ramirez and M. Lopez-Edwards

Virulence of several isolates of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metsch.) Sor. and Paecilomyces fumosoroseus (Wize) Brown & Smith were evaluated on adult weevils of Anthonomus fulvipes Boheman at dose of 108 spores/mL under laboratory conditions. The study was complemented by testing one isolate each of M. anisopliae and P. fumosoroseus against adult weevils on organically grown Barbados cherry trees at dose of 2 × 1015 spores/ha. All fungi species showed high virulence against A. fulvipes adults, with mortality ranging from 92% to 100%. LT50 values varied 2.7 to 4.8 d. The M. anisopliae isolate 10, and the P. fumosoroseus isolate 1 were selected for field evaluation because laboratory insect cadavers presented the best sporulation. After applying the fungi to the trees, total weevil captures were 38, 56, and 100 for the P. fumosoroseus, M. anisopliae, and the check (untreated) plots, respectively. Statistical differences in fruit damage were detected among treatments: M. anisopliae and P. fumosoroseus treatments showed an average of 50% of undamaged fruits, whereas in the control plots presented 36% of undamaged fruits. Laboratory and field experiments suggest that entomopathogenic fungi have a potential as microbial control agents against the weevil A. fulvipes in organically grown Barbados cherry trees.

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Martha Elena Pedraza-Santos, David Jaen-Contreras, M. Alejandra Gutièrrez-Espinosa, Teresa Colinas-Leon and Cristina Lopez-Peralta

Effects of inoculation with arbuscular endomycorrhizal fungi (Acaulospora scrobiculata and Glomus mosseae) on acclimatization and growth of chrysanthemum (Dendrathema glandiflora Tzevelev) plants, propagated in vitro, under different conditions of fertilization (0, 20, and 40 mg·L-1 of NPK) were studied. Mycorrhizal colonization did not influence surviving percentage of chrysanthemum plantlets during the acclimatization stage; however, we could colonize the developing roots and reduce the amount of inoculum needed and beneficial effects on plant growth were obtained during early stages of colonizing. Plant growth in greenhouse was regulated by synergism between the effect of endomycorrhizal fungus type and soil fertilization with N, P, and K. Effects of A. scrobiculata were observed as an increasein number of leaves, leaf area, stem diameter, root volume and fresh and dry weight of leaves, stem and root. The G. mosseae fungus improved N, P, Mg, and Zn content in leaves; P, K, Ca, Mg, and Zinc in stem and Ca content in root. On the other hand, A. scrobiculata only increased N content in leaves, stem and roots; P content in leaves and roots, and Ca content in stem. Percentage of mycorrhizal colonization on roots was affected by adding N, P, and K to soil. The highest values were obtained with fertilization doses of 20 mg·L-1. The number of spores of mycorrhizal fungi was increased by adding fertilizer to soil (40 mg·L-1 of NPK).

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Roberto Lezama-Gutierrez, Jaime Molina-Ochoa, Oscar L. Contreras-Ochoa, Martin Gonzalez-Ramirez, Oscar Rebolledo-Dominguez and M. Lopez-Edwards

The susceptibility of third-instar larvae of Anastrepha ludens (Loew) to the entomopathogenic nematodes Steinernema carpocapsae (Weiser) (All and Tecomán strains), S. feltiae (Filiipjev), S. glaseri (Steiner) (NC strain), S. riobrave (Cabanillas, Poinar & Raulston), and Heterorhabditis bacteriophora Poinar (NC, Patronato, and Tecomán strains), was evaluated under laboratory conditions. Sterile distilled water (1.0 mL) with 4000 infective juvenile nematodes were applied on 300 g of moistened sterile soil into 1000-mL pots, and 20 third-instar larvae were placed on the soil surface, 1 mL of distilled water without nematodes was applied as control. Each nematode treatment was replicated four times. After nematode application, pots were incubated at 25 °C. Mortality of larvae and pupae was evaluated 6 and 12 d after inoculation. Cadavers of larvae and pupae were dissected and examined for the presence of nematodes. Our results showed that Mexican fruit larvae were susceptible to entomopathogenic nematodes. S. riobrave and S. carpocapsae All strain caused 90% of larval and pupae cumulative mortality, H. bactetiophora NC strain and S. feltiae killed more than 80%, whereas H. bacteriophora Tecomán and S. glaseri caused a 52.5% mortality. These results suggest that the nematodes S. riobrave and S. carpocapsae All strain have a potential as biological control agents against A. ludens.

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Edward J. Boza, Juan Carlos Motamayor, Freddy M. Amores, Sergio Cedeño-Amador, Cecile L. Tondo, Donald S. Livingstone III, Raymond J. Schnell and Osman A. Gutiérrez

Cacao (Theobroma cacao L.) is an important cash crop in tropical growing regions of the world and particularly for small cacao farmers. Over the past two decades, ‘CCN 51’ has become one of the most planted cultivars in Ecuador, mainly as a result of its high productivity and disease resistance. Intermixing of Nacional fine flavor Ecuadorian beans with beans of ‘CCN 51’ has become common practice, reducing overall bean quality and decreasing value. The primary goals of this study were to determine the genetic identity, structure, and allelic richness of ‘CCN 51’, its maternal origin and to compare ‘CCN 51’s’ agronomic characteristics against a composite group of Nacional cultivars. To investigate the complex genetic background of this cultivar, 70 simple sequence repeat loci were used. The high heterozygosity observed (56 of 70 loci) for ‘CCN 51’ is not characteristic of traditional Nacional cultivars. Comparison of agronomic characteristics between ‘CCN 51’ and several Nacional cultivars indicates significant differences in cacao dry bean weight, yield potential, production efficiency, percent healthy pods, and witches' broom [Moniliophthora perniciosa (Stahel) Aime & Phillips-Mora] disease incidence. Additionally, physical, chemical, and organoleptic characteristics suggest that ‘CCN 51’ is different from those of Nacional lineage. Based on population structure analysis, the predominant ancestries for ‘CCN 51’ are Iquitos (45.4%), Criollo (22.2%), and Amelonado (21.5%) genetic groups. A lesser proportion of its genome was accounted for by genetic groups Contamana (3.9%), Purús (2.5%), Marañon (2.1%), and Nacional (1.1%) admixtures. Results of phylogenetic analyses using the unweighted pair group method with arithmetic mean yielding high bootstrap values strongly support the relatedness of ‘CCN 51’ with Iquitos, Criollo, and Amelonado genetic groups. Moreover, seven mitochondrial simple sequence repeat loci revealed that ‘CCN 51’ maternally inherited the ‘IMC 67’ cytotype. ‘CCN 51’ constitutes a valuable cacao genetic resource that is currently used not only in its country of origin, but also in many other national breeding and selection programs worldwide.

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Elvia C. Palacios-Torres, M. Alejandra Gutièrrez-Espinosa, Gloria A. Moore, Gustavo Mora-Aguilera, Daniel L. Ochoa-Martínez and Angel Villegas-Monter

Citrus Tristeza Closterovirus (CTV) induces mild and/or severe symptoms on Citrus species. It may cause death of trees if the rootstock-scion combination is susceptible. It has been found in other plant/virus combinations that transformation with partial or complete viral genes (e.g., coat protein genes) can confer resistance to the resulting transgenic plants. We previously reported A. tumefaciens mediated transformation and production of two sour orange (C. aurantium L.) plants expressing the coat protein gene of CTV, which was the first report of production of transgenic Citrus using a viral gene. However, in order to properly evaluate resistance, it is necessary to obtain as many transgenic Citrus plants from single transformation events as possible. Therefore, we are currently transforming grapefruit (Citrus paradisi) `Marsh' and `Star Ruby' and sweet orange (C. sinensis) `Valencia' with CTV coat protein genes. These species are susceptible to CTV and more amenable to transformation than sour orange. Epicotyl segments of etiolated seedlings were inoculated with A. tumefaciens strain EHA101 harboring binary plasmid pGA482GG containing the coat protein gene of mild Florida CTV strain T30 (CP-T30) or severe Florida strain T36 (CP-T36). Putatively transformed shoots were regenerated on selection medium containing kanamycin. Regenerated shoots were evaluated with GUS assays; those shoots positively identified by GUS were then evaluated with PCR. We have currently identified 17 `Marsh' grapefruit, 20 `Star Ruby' grapefruit, and seven sweet orange putatively transformed plants.