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Jose Lopez-Medina, B.J. Murphy, and J.N. Moore

Isozyme staining and SDS-PAGE of soluble proteins were performed using leaf homogenates from 6- to 8-month-old field-grown seedlings resulting from the cross of either `Heritage' or `Nova' raspberry with ARK-577 diploid blackberry, the latter used as the pollen-donor parent. Four enzyme systems were tested: ADH, PGM, MDH, and PGI. Of these, ADH and PGM did not show any activity; MDH was monomorphic in both raspberry and blackberry parents, with activity at the same migration distance. PGI was polymorphic in the two raspberry cultivars, showing three dimeric bands, but monomorphic in blackberry; the allele for PGI in blackberry being common to that allele coding for the most cathodal band in raspberry. This phenomenon, in addition to poor resolution of bands (due, perhaps to low enzyme activity) and evidence of accidental self-pollination in our populations, prevented us from positively identifying the hybrid offspring using isozymes. By SDS-PAGE of soluble proteins, two bands were detected that seemed to be unique to ARK-577 blackberry and were also expressed in some of the offspring, suggesting a hybrid origin of these seedlings. Morphological comparisons indicated that those seedlings possessing the two unique bands highly resemble the blackberry male parent, greatly supporting their hybrid origin. Unless additional analysis shows otherwise, SDS-PAGE can be used to identify Raspberry–Blackberry hybrids during their vegetative stage of development, and might prove applicable to other interspecific hybrids of Rubus.

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B. de los Santos, C. Barrau, C. Blanco, F. Arroyo, M. Porras, J.J. Medina, and F. Romero

Several preplant soil fumigation treatments were repeated over a period of three years on strawberry (Fragaria ×ananassa Duchesne) crops, at two different places in the province of Huelva (southwestern Spain). The influence of these treatments on Trichoderma soil populations and on populations of soilborne pathogens was examined every year by isolating soil onto selective media. No strawberry pathogens were detected but Trichoderma soil populations increased each year after the treatment. Significant differences were noted between the treatments and also compared to the control. The largest populations were observed after treatments with methyl bromide and chloropicrin, and so resulting in a higher production. Chemical name used: trichloronitromethane (chloropicrin).

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Neusa M.C. Stenzel, Carmen S.V.J. Neves, José C. Gomes, and Cristiane C. Medina

This study reports the performance (yield, tree size, and fruit quality) of 'Ponkan' mandarin (Citrus reticulata Blanco) on seven rootstocks, evaluated for 11 years under Southern Brazil conditions. Trees on C13 citrange had higher cumulative yield for seven harvests than those on trifoliate orange. Cleopatra mandarin, rough lemon, Rangpur lime, Sunki mandarin, and Volkamer lemon rootstocks maintained their values at an intermediate position and did not present any significant difference regarding C13 citrange, and trifoliate orange. Trees on C13 citrange and on trifoliate orange exhibited the lowest alternate bearing index. Cleopatra mandarin induced the greatest canopy volume, but it was not significantly different from Sunki mandarin and rough lemon. The smallest trees were those on Volkamer lemon and trifoliate orange. The highest yield efficiency came from trees on C13 citrange and the smallest on Cleopatra mandarin. Rootstocks did not significantly affect fruit weight.

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Bielinski M. Santos, José Manuel López-Aranda, James P. Gilreath, Luis Miranda, Carmen Soria, and Juan J. Medina

Tunnel and open field trials were conducted in two locations in Huelva, Spain, and one in Florida to determine the effect of selected methyl bromide (MBr) alternatives on strawberry yield. In Spain, the tunnel treatments were: a) nontreated control, b) MBr + chloropicrin (Pic) 50:50 at a rate of 400 kg·ha–1; c) dazomet at 400 kg·ha–1, d) 1,3-dichloropropene (1,3-D) + Pic 65:35 at 300 kg·ha–1; e) Pic at 300 kg/ha; f) dimethyl disulfide (DMDS) + Pic 50:50 at 250 + 250 kg·ha–1; and f) propylene oxide at 550 kg·ha–1. All treatments were covered with virtually impermeable film (VIF), except the nontreated control, which was covered with low-density polyethylene (LDPE) mulch. Dazomet was rototilled 10 cm deep, whereas the other fumigants were injected with four chisels per bed. In Florida, the open-field treatments were a) nontreated control, b) MBr + Pic 67:33 at a rate of 400 kg/ha with LDPE; c) MBr + Pic 67:33 at 310 kg·ha–1 with VIF; d) 1,3-D + Pic 65:35 at 300 kg·ha–1 with VIF; e) methyl iodide (MI) + Pic 50:50 at 230 kg·ha–1 with VIF; f) Pic at 300 kg·ha–1 with VIF; g) DMDS + Pic 50:50 at 250 + 250 kg·ha–1 with VIF; and g) propylene oxide at 500 kg·ha–1 with VIF. The fumigants were applied with three chisels per bed. In Spain, the results showed that 1,3-D + Pic, DMDS + Pic, and Pic consistently had similar marketable yields as MBr + Pic. Similar results were found in Florida, with the exception of propylene oxide, which also had equal marketable fruit weight as MBr + Pic.

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Pedro Domínguez, María T. Ariza, Juan J. Medina, Berta de los Santos, Manuel Chamorro, José M. López-Aranda, and Carmen Soria

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Eva García-Méndez, David García-Sinovas, Maximo Becerril, Antońeta De Cal, Paloma Melgarejo, Anselmo Martínez-Treceño, Steven A. Fennimore, Carmen Soria, Juan J. Medina, and Jóse M. López-Aranda

The phase out of methyl bromide (MB) requires effective alternatives for soil disinfestation, particularly in high-elevation strawberry (Fragaria × ananassa Duch.) nurseries. Methyl bromide alternative fumigants were evaluated over a 3-year period for weed control and runner plant yields at strawberry nurseries in Spain. Two types of field trials were carried out: replicated experiments and commercial-scale field demonstrations. In the replicated experiments, eight fumigant treatments were evaluated each year, including the nonfumigated control and commercial standard methyl bromide plus chloropicrin mixture (MB : Pic) (50 : 50 w/w). Among the treatments evaluated were dazomet, chloropicrin (Pic) alone, metam sodium plus chloropicrin (MS + Pic), 1,3-dichloropropene:chloropicrin (1,3-D : Pic) (61 : 35 w/w), DMDS plus chloropicrin (DMDS + Pic), and propylene oxide. The best alternative fumigant treatments from the replicated experiments were carried forward to the demonstration phase of the project. Treatments such as 1,3-D : Pic (300 kg·ha−1), the combination of metam sodium plus chloropicrin (Pic) (400 to 500 + 150 to 250 kg·ha−1), Pic alone (300 kg·ha−1) as well as dazomet (400 kg·ha−1) controlled weeds at the level of MB : Pic (400 kg·ha−1). Runner plant yields, in soils previously fumigated with alternative fumigants varied, among years, locations, and trial scale, i.e., commercial scale, or small plot. By comparison, runner plant yields in MB : Pic-fumigated soils were consistently high among years, location, and trial scale. Chemical names used are: 1,3-D, 1,3-dichloropropene; MB, methyl bromide; Pic, trichloronitromethane; MS, sodium N-methyldithiocarbamate; DMDS, dimethyl disulphide; dazomet, tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione; PO, propylene oxide

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Carmen Soria, Juan J. Medina, Pedro Domínguez, María T. Ariza, Luis Miranda, Rosalía Villalba, Josefa Gálvez, José F. Sánchez-Sevilla, Iraida Amaya, Rafael Sesmero, and José M. López-Aranda

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Pedro Domínguez, Juan J. Medina, José M. López-Aranda, María T. Ariza, Luis Miranda, Iraida Amaya, José F. Sánchez-Sevilla, Rosalía Villalba, and Carmen Soria

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José M. López-Aranda, Carmen Soria, José F. Sanchez-Sevilla, Josefa Gálvez, Juan J. Medina, Antonio Arjona, José I. Marsal, and Rafael Bartual

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José M. López-Aranda, Carmen Soria, José F. Sánchez-Sevilla, Josefa Gálvez, Juan J. Medina, Antonio Arjona, José I. Marsal, and Rafael Bartual

Public and private institutions in Spain are increasing strawberry (Fragaria ×ananassa Duch.) breeding efforts to obtain new strawberry cultivars well-adapted to growing conditions in Huelva and other Spanish areas, such as Valencia on the eastern Spanish coast. The new `Medina' is a short-day cultivar that is remarkable for its high production of first quality fruits, and large fruits. `Medina' has also an appropriate harvest calendar for the economic interest of the Huelva area.