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Francisco Doñas-Uclés, Diego Pérez-Madrid, Celia Amate-Llobregat, Enrique M. Rodríguez-García and Francisco Camacho-Ferre

In the southeast of Spain, specifically in the province of Almería, pepper production represents 1.70% of the total pepper (Capsicum annuum L.) production in the world, which in turn represents 31.8% of the European production. In the last 10 years, production has remained stable between 7,240 and 10,997 ha. Due to the economic importance of this crop in the region, more improvements of the production techniques have been adopted. The reduced number of commercial rootstocks of peppers, which really improve yield in this crop, causes a continuous search for new genotypes. In this experiment, five pepper rootstocks were evaluated in an experimental design of randomized blocks with six treatments and three repetitions. The rootstocks used were: ‘Serrano de Morelos 2’ (SCM-334), ‘Jalapeño’, ‘Oscos’, ‘AR 9604040’, and ‘Tresor’. The cultivar grafted onto them was ‘Palermo’ also used as a control test. SCM-334 cultivar used as rootstock has a similar behavior in the production parameters measured as the commercial pepper rootstocks which were used. ‘Jalapeño’ and ‘SCM-334’ demonstrated different behavior in plant vigour compared with the others treatments. There is no interrelationship between production and plant vigour provided by the rootstock.

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Marcelino Bazán-Tene, Jaime Molina-Ochoa and Enrique Alejandro Bracamontes-Ursúa

Hot pepper (HP), Capsicum annuum (L.), is a solanum plant domesticated in Mesoamerica. It is currently widespread worldwide, and its uses are varied, such as an excellent flavoring, pigment base, and as a food resource with source of vitamins. The seven top world producers of HP are China, Mexico, Turkey, Spain, United States, Nigeria, and Indonesia. Mexico is producing about 623,238 t/year of fresh fruits in 136,398 ha; Colima produced 17,181 t in 676 ha, with a mean of 27 t·ha-1. The culture of HP in Colima is facing certain limitations in showing its productive potential, such as maintaining fertile and well-drained soils, and constant soil moisture; being weed-free during the first weeks after transplanting; and sustaining plant uniformity into transplantation. Transplantation is made in seed beds, but there is a lack of scientific evidence on shade requirements in the seed nursery to accelerate and improve plant quality for transplanting, and to impact on fruit yield. The aim was to evaluate the effect of levels of shading on the germination and vegetative development of `Serrano' HP under greenhouse conditions. Four levels of shading were evaluated using mesh fabrics to produce 90%, 75%, and 50% shade, and a control without shading on the seed beds. A completely randomized design with four treatments and four replications was used. The shading treatments reduced the germination period in about 1 day, increased the percentage of germination with a range between 1.75% and 3.25%; increased the plant height 0.83, 2.85, and 4.38 cm at 3, 6, and 10 days post-emergence; increased the root biomass about 0.01 g/plant, and 0.24 g of fresh foliage with the 90% shade compared with the control. Overall, a better agronomic performance of `Serrano' HP was obtained with 90% shading.

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Chunxian Chen, Jude W. Grosser, Milica Ćalović, Patricia Serrano, Gemma Pasquali, Julie Gmitter and Fred G. Gmitter Jr

tetraploid rootstock breeding program. Literature Cited Ananthakrishnan, G. Calovic, M. Serrano, P. Grosser, J.W. 2006 Production of additional allotetraploid somatic hybrids combining mandarins and

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M. López-Serrano and A. Ros Barceló

Levels and histochemical localization of peroxidase and polyphenol oxidase, and levels of anthocyanins and (+)-catechin, were studied in fruit of two strawberry (Fragaria ×ananassa Duch.) cultivars (`Oso Grande' and `Chandler'), which show different degrees of susceptibility to enzymatic browning after processing. Although the levels of anthocyanins at the processing-ripe stage may be important in determining pigment stability, and therefore market suitability, the color stability of `Chandler' is apparently determined by the lower endogenous levels of peroxidase and polyphenol oxidase in the processing-ripe stage, which are also accompanied by a lower (+)-catechin content. Polyphenol oxidase was localized almost exclusively in the cortex and to a lesser extent in the pith, showing a complementary pattern to that shown by peroxidase, which was localized in the vascular bundles. Since peroxidase and polyphenol oxidase showed a complementary localization pattern in the fruit, these results strongly suggest a synergic role for these two oxidative enzymes in pigment decay and the associated browning reaction, which occurs in processed strawberry fruit and their derived foods.

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Brent Rowell, R. Terry Jones, William Nesmith, April Satanek and John C. Snyder

Bacterial spot epidemics, caused by Xanthomonas campestris pv. vesicatoria (Xcv), are still considered serious risks for commercial pepper (Capsicum annuum) growers in a number of eastern, southern and midwestern states. Newly released bell pepper cultivars with the Bs2 gene for resistance to Xcv races 1, 2, and 3 were compared in 2000 under bacterial spot-free and severe (natural) bacterial spot epidemic conditions in central and eastern Kentucky where similar trials had been conducted from 1995 to 1997. In addition to the replicated bell pepper trials, 49 hot and specialty pepper cultivars were grown for observation in single plots at the same two locations. As in previous trials, there were economically important differences in resistance and marketable yields among bell pepper cultivars having the Bs2 gene; some resistant cultivars were as susceptible as susceptible checks. Others were highly resistant in spite of the presence of Xcv races 3 and 6 in the eastern Kentucky trial. Only a few were highly resistant with excellent fruit quality. With a few notable exceptions, most of the hot and specialty cultivars were very susceptible to bacterial spot. Two of the three new jalapeño cultivars carrying Bs2 were highly resistant to bacterial spot and high yielding under severe epidemic conditions.

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Jude W. Grosser, Victor Medina-Urrutia, Govindarajulu Ananthakrishnan and Patricia Serrano

Sour orange has been a premier citrus rootstock worldwide due to its ability to perform on challenging soils and to produce and hold high-quality fruit. However, increasingly widespread quick-decline isolates of citrus tristeza virus (CTV) have destroyed entire industries on sour orange in some countries, and are in the process of destroying millions of trees on sour orange in Florida. CTV also threatens other citrus locations planted heavy to sour orange, including Texas and Mexico. An acceptable alternative rootstock to replace sour orange is in high demand but has yet to be developed. Molecular analyses have recently determined that sour orange is probably a hybrid of pummelo and mandarin. We report the production of 12 new mandarin + pummelo somatic hybrids produced by protoplast fusion from selected superior mandarin and pummelo parents, in efforts to develop a suitable replacement sour-orange-like rootstock that is resistant to CTV-induced quick decline. Somatic hybrids from all 12 parental combinations were confirmed by a combination of leaf morphology, flow cytometry, and RAPD analyses (for nuclear hybridity). These new mandarin + pummelo somatic hybrids are being propagated by rooted cuttings as necessary to conduct quick-decline resistance assays and to assess horticultural performance in replicated field trials.

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G. Martínez, M.T. Pretel, M. Serrano and F. Riquelme

Resistance (R) to preloaded gas diffusion was used to follow the evolution of R during cherimoya fruit maturation and senescence. Cherimoya ethane diffusion was linear and gave an R value of 2048 ± 167 s·cm-1 for preclimacteric fruit. R increased linearly during maturation, and significant differences were noted between fruit in which diffusion through the stem scar was or was not blocked with petroleum ielly.

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M. Serrano, F. Romojaro, J.L. Casas and M. Acosta

We have compared the ethylene and polyamine metabolism of senescing flowers from two cultivars of carnation (Dianthus caryophyllus L.), one showing climacteric (`Arthur') and the other non climacteric behavior (`Killer'). `Arthur' carnations showed the first symptoms of senescence at day 7, coinciding with maximum ethylene and CO2 production, a peak in the ethylene-forming enzyme (EFE) activity, and a 7-fold increase in free ACC content in respect to the initial value. In `Killer' carnations, however, onset of senescence was 15 days after harvest, and no ethylene or CO2 peak was detected. The lack of ethylene production was due to a constantly low level of free ACC and a low EFE activity. Free polyamine distribution was similar in the two cultivars at the preclimacteric stage, with the spermidine content being about three times that of putrescine. But as senescence progressed, this situation was reversed in `Arthur' carnation, with a predominance of putrescine during the senescence, while it was maintained in `Killer', with no significant changes during senescence. No free spermine was found at any stage of senescence in either cultivar. Thus, a correlation exists between ACC level, distribution of polyamides, and longevity of cut carnation flowers. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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Robert Savé, Josep Peñuelas, Oriol Marfà and Lydia Serrano

Field-grown strawberry (Fragaria × annanasa Duch. cv. Chandler) plants were subjected to two irrigation regimes from Nov. 1989 to July 1990 to evaluate the physiological and morphological effects of mild water stress. Irrigation was applied when soil matric potential reached -10 and-70 kPa for the wet and dry treatments, respectively. During the spring, these regimes did not promote significant changes in plant water relations, transpiration rates, plant morphology, or canopy architecture. However, during the summer, after several stress cycles, significant differences between treatments were observed. Pressure-volume curves of dry-treatment plants indicated that leaf osmotic potentials, measured at full and zero turgor, decreased 0.2 to 0.4 MPa. This decrease in osmotic potential also was accompanied by a 50% increase in the modulus of elasticity for these water-stressed plants compared to well-watered plants. Dry-treatment plants also showed stress avoidance mechanisms in changes of whole-plant morphology and canopy architecture, from monolayer to polylayer leaf distribution and leaf orientation from south to north. Despite what would appear to be useful drought-resistance strategies, there was significantly lower fruit production by plants grown under the dry treatment.

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María Serrano, Ma Concepción Martínez-Madrid and Félix Romojaro

Treatment of cut `Master' carnations (Dianthus caryophyllus L.) with 50 mm aminotriazole (ATA) in distilled water for 5 days retarded senescence, increased flower longevity by 4 days compared to the control carnations kept in distilled water and inhibited the climacteric peak of ethylene production normally produced during the senescence of these flowers. The treatment had no effect, however, on the levels of the polyamines putrescine and spermidine. Thus, the biosynthetic routes of ethylene and polyamines may not compete for the common precursor S-adenosylmethionine (SAM). Also, in the petals of the control carnations, increased ethylene production was correlated with increased ion leakage and abscisic acid (ABA) levels. In the ATA treated petals, ion leakage and ABA levels increased later and reached values less than 50% compared to the control carnations. Chemical names used: abscisic acid (ABA), 3-1H-amino-1,2,4-triazole-1-yl (aminotriazole), 1-aminocyclopropane-1-carboxylic acid (ACC), S-adenosyl methionine (SAM).