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  • Author or Editor: M. Sakin x
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Auxin induction of ethylene, and fruit growth rates were investigated as early indicators of NAA thinning response for Golden Delicious, Red Delicious, McIntosh, Empire, and Tydeman's Red over a four period. Abscission at the end of the drop period was correlated with ethylene evolution from leaves 24-48 hours after NAA application and with changes in fruit growth at 2-3 day intervals through 10-14 days after application. Variation in ethylene evolution and fruit growth were also associated with environmental conditions prior to and at the time of NAA application to determine which factors have the greatest influence on response. Ethylene was a better predictor of final fruit drop than changes in fruit size for all varieties tested. However both performed very well. The ethylene bioassay requires more equipment, but the response is more-immediate. Bourse, and spur leaves as well as fruit were capable of producing ethylene in response to NAA application. Thinning response was greatest when all leaves and fruit were treated with NAA, followed by the bourse and spur leaves. Little or no response was produced when the fruit alone were treated. Concentration experiments and radioisotope data indicate that ethylene response is directly related to the amount of NAA absorbed. Regression analysis indicates that approximately 60% of the variation in response can be predicted by ethylene evolution

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The genes that determine cyclic flowering in all commercially grown cultivars of strawberry (Fragaria ×ananassa Duch.) were derived from a single source of F. virginiana ssp. glauca from the Wasatch Mountains in Utah. To broaden the germplasm base of cyclic flowering cultivars, we evaluated the reproductive characteristics of 5 to 10 colonies of F. virginiana ssp. glauca from each of 32 Rocky Mountain sites ranging in elevation from 700 to 2900 m. Populations at high and low elevations had high percentages of putative day neutrals with cyclic flowering (43% to 100%) and hermaphrodites (20% to 80%), although most hermaphrodites were only partially fertile. There was also little association between elevation and crown numbers or flower number per cycle, but the total number of flowers per plant was negatively correlated with elevation. Fruit size was not significantly correlated with fruit number. When the data were subjected to a principal component analysis, two distinct groups were identified: one from the Black Hills of South Dakota and the other from low-elevation sites in Idaho and northwestern Montana. These patterns mirrored previously described patterns based on leaf traits.

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Twenty-one western and 13 eastern strawberry [Fragaria × ananassa (Duch.)] cultivars were grown in a polyethylene-covered greenhouse (polyhouse) in deep beds at either 10 × 10 or 25 × 25 cm spacing. Runners were removed weekly from the closest-spaced plants (hills), and the more open-spaced plants were allowed to set four runners on each side of the mother plant before the runners were removed (matted rows). Temperatures were allowed to fluctuate normally in the polyhouse, except that winter temperatures were maintained above 0C. The average yield of eastern and western cultivars did not differ significantly in most comparisons, but the average fruit weight of the Californian cultivars was significantly higher than the eastern ones, and Californian cultivars allocated a higher proportion of their biomass to reproduction. Nonbearing plants of eastern and western cultivars produced similar numbers of runners per plant and daughters per runner. There was no significant relationship between CO2 assimilation rate and yield. Interbreeding eastern cultivars with the most productive western genotypes might result in increased yields, but only if the higher reproductive efforts of the western types can be captured and transferred.

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