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  • Author or Editor: José Manuel López-Aranda x
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Unlike other important crops analyzed so far for genetic diversity and population structure, the brief history and particularities of the genetics of the cultivated strawberry (Fragaria ×ananassa Duchesne) have limited its genetic characterization. The genomic composition and the pattern of inheritance have not been fully elucidated, although a number of studies have suggested a highly diploidized genome. In this study, the similarity relationships and structure of 92 selected strawberry cultivars with widely diverse origins have been established using simple sequence repeat (SSR) markers derived from expressed sequence tags (EST-SSR markers). Genetic analysis performed by the unweighted pair group method with arithmetic mean clustering revealed a distribution according to both date of cultivar release and breeding for a specific climatic adaptation. Additionally, a model-based clustering approach identified three populations among the strawberry cultivars with an overall FST value of 0.15 to 0.16. Both analyses support a limited differentiation of modern cultivars, most probably as a consequence of the methodology of strawberry breeding. Interestingly, the collection of strawberry cultivars here analyzed showed comparable genetic differentiation to that observed in natural populations of Fragaria chiloensis (L.) Mill., one of its wild ancestors. Our results suggest that breeding has produced a small but significant reduction on the genetic diversity of F. ×ananassa. The panel of 10 EST-SSRs described in this work provided an extremely low probability of confusion (less than 10−11), offering an efficient and accurate method for cultivar identification.

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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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