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  • Author or Editor: Maria I. Alvarez x
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Flower thinning of pears has advantages over fruit thinning in that the earlier it is performed the greater the potential effect on fruit size. At the Comahue National Univ. in Argentina (lat. 38°56' 67°59'W), lime sulphur was evaluated as flower thinner on 10-year-old `AbbAbbé Fetel' (Pyrus communis L.) pear trees trained to palmette leader. Cultural practices were similar to those of commercial orchards in the High Valley. Treatments were 1) control, and 2) 7% lime sulphur, applied on 16 Sept. 2002 (30% bloom) using an orchard sprayer. Fruit diameter (FD) was recorded two weekly (n = 20 per date and treatment). At 144 days after full bloom (DAFB), or initial commercial harvest, crop load, fruit weight and the maturity indices were determined. Fruits were then graded into size categories. Growth equations were developed with SYSTAT procedure and mean separations were computed with Student's t-test. Mean FD was significantly increased by the lime sulphur sprays, starting from 115 DAFB. Logistic models best fitted the fruit growth vs. time curves. The equation was: FD = 77.87/1+e2.26-0.03DAFB (R 2 = 0.97), for the non-thinned trees. Treatment 2 increased the percentage of fruits ≥70mm by 42.16%. At 144 DAFB, thinned trees showed firmer fruits than the controls (64.4 vs. 61.7 N) and there were no statistical differences among treatments in soluble solids concentration and starch index; the values were 11.5 °Brix and 3.55, respectively, for the control fruits. Consequently, our data indicate that lime sulphur applied at 30% bloom was an effective practice to thin `Abbé Fetel' pears and to enhance fruit quality at ripening.

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Fluorescent proteins (FT) have become essential, biological research tools. Many novel genes have been cloned from a variety of species and modified for effective, stable, and strong expression in transgenic organisms. Although there are many applications, FT expression has been employed most commonly at the cellular level in plants. To investigate FT expression at the whole-plant level, particularly in flowers, petunia ‘Mitchell Diploid’ [MD (Petunia ×hybrida)] was genetically transformed with seven genes encoding FTs: DsRed2, E2Crimson, TurboRFP, ZsGreen1, ZsYellow1, rpulFKz1, or aeCP597. Each gene was cloned into a pHK-DEST-OE vector harboring constitutive figwort mosaic virus 35S promoter and NOS-terminator. These plasmids were individually introduced into the genome of MD by Agrobacterium tumefaciens–mediated transformation. Shoot regeneration efficiency from the cocultured explants ranged from 8.3% to 20.3%. Various intensities of red, green, and yellow fluorescence were detected from TurboRFP, ZsGreen1, and ZsYellow1-transgenic flowers, respectively, under ultraviolet light for specific excitation and emission filters. More than 70% of plants established from the regenerated shoots were confirmed as transgenic plants. Transgenic ZsGreen1 petunia generated strong, green fluorescence in all flower organs of T0 plants including petals, stigmas, styles, anthers, and filaments. Most of the chromophores were localized to the cytoplasm but also went into the nuclei of petal cells. There was a positive linear relationship (R 2 = 0.88) between the transgene expression levels and the relative fluorescent intensities of the ZsGreen1-transgenic flowers. No fluorescence was detected from the flowers of DsRed2-, E2Crimson-, rpulFKz1-, or aeCP597-transgenic petunias even though their gene transcripts were confirmed through semiquantitative reverse transcriptase-polymerase chain reaction. T1 generation ZsGreen1 plants showed green fluorescence emission from the cotyledons, hypocotyls, and radicles, which indicated stable FT expression was heritable. Four homozygous T2 inbred lines were finally selected. Throughout this study, we demonstrated that ZsGreen1 was most suitable for generating visible fluorescence in MD flowers among the seven genes tested. Thus, ZsGreen1 may have excellent potential for better utility as a sensitive selectable marker.

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