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Ryan N. Contreras, Ron Determann, and Mara Friddle

green. Our hypothesis was that a difference in ploidy level among cultivars is related to the variation in winter color and that cultivars that remain greener during winter were tetraploids. The current study was conducted to determine the ploidy level

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Adolfo Rosati, Andrea Paoletti, Raeed Al Hariri, Alessio Morelli, and Franco Famiani

The higher productivity of modern fruit tree cultivars, compared with wild trees, is mostly related to their higher partitioning of dry matter into fruit [i.e., higher harvest index (HI)] ( Patrick, 1988 ), rather than to differences in

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Ralph Scorzal, Lisa G. May, Beverly Purnell, and Bruce Upchurch

The growth in diameter of large-(`Loring' and `Suncrest') and small-fruited (`Bailey' and `Boone County') peaches [Prunus persica (L.) Batsch] was recorded at weekly intervals from 175 days prebloom to ripening. Samples collected at three dates prebloom, full bloom (FB), and four dates postbloom, including ripe fruit, were sectioned and stained. Total cell count and mean cell size were determined for prebloom ovaries and postbloom mesocarp tissue. Large-fruited cultivars had significantly more cells (up to 3.7 times) than small-fruited cultivars at all sampling dates. Cell sizes increased dramatically with fruit development, but were similar for all cultivars within each sampling date. These results suggest that mesocarp cell count is the major difference between small- and large-fruited peach cultivars and that this difference is determined early in the growth of the ovary.

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J. Cuevas, L. Rallo, and H.F. Rapoport

We have compared reproductive processes and fruit set in Manzanillo and Frantoio olive cultivars which are reported in the literature respectively as incompatible and partially compatible. The same incompatibility reaction was observed in both cultivars. Pollen tube growth was almost completely inhibited beyond the stigma, but some degree of self-fertilization was accomplished. However, in both cultivars cross-pollination provided a earlier and higher level of fertilization. Differences in self-incompatibility behavior seemed related to the level and the amount of delay in self-fertilization. In the compatible variety, Frantoio, self-pollen tube growth was accomplished more rapidly and showed a higher level of self-fertilization than in the incompatible Manzanillo cultivar. Fruit set matched reproductive behavior.

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Fruit growth in saskatoons (Amelanchier alnifolia Nutt.), an emerging horticultural crop across the Canadian prairies, results from development of the mesocarp and the endocarp-locular-ovular structure which includes the developing seeds. Contribution of these tissues to fruit size was assessed using transverse sections of ovaries sampled at six developmental stages among large- and small-fruited cultivars. Mesocarp development was similar among the larger-fruited cultivars (Thiessen, Northline, and Smoky); the number of cells increased rapidly through Stage I [162 to 293 growing degree days (GDDs)] of fruit growth, and cell number increase was minimal during Stages II (293 to 577 GDDs) and III (577 to 747 GDDs). In `Regent' fruit (a small-fruited cultivar), the maximal rate of cell division was delayed until Stage II and the mesocarp contained fewer cells than the larger-fruited cultivars at harvest maturity. Mesocarp cell enlargement was similar among all of the cultivars studied where cell expansion was maximal during Stage I and continued at a slower rate during Stages II and III. The area of the endocarp-locular-ovular structure was greatest for `Thiessen' and `Northline', midrange for `Smoky', and smallest for `Regent'. Data suggest that a minimum number of mesocarp cells early in fruit development is required to attain maximal mesocarp size, and that differences in cultivar fruit size are a function of both the mesocarp and the endocarp-locular-ovular structure.

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A.D. Turner and H.C. Wien

Cultivars of bell pepper differ in susceptibility to bud/flower abscission. Reduction in the level of assimilate, and alterations in assimilate partitioning may be involved in the processes leading to bud/flower abscission. Four growth analysis experiments were conducted to determine whether two pepper cultivars differing in susceptibility to stress-induced abscission showed corresponding differences in growth and rates and dry matter partitioning when subjected to shade stress. The reduction in RGR and NAR with shading was significantly greater for the abscission-susceptible `Shamrock' than the more tolerant `Ace'. Partitioning of dry matter to reproductive structures was reduced by shading. There were no cultivar differences in the proportion of dry matter partitioned to young developing leaves. Fully expanded leaves comprised a larger proportion of total dry matter in `Shamrock'. The lower NAR of `Shamrock' under stress may have led to greater bud/flower abscission than `Ace' under shade stress. If preferential partitioning of dry matter to competing structures (developing leaves) is also involved, it was not detected using this technique.

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Howard F. Harrison Jr. and Mark W. Farnham

, Legacy, and Patron) and four hybrid cabbage cultivars (Bravo, SC 100, Stonehead, and Vantage Point) were chosen for this study based on differences in tolerance observed in a preliminary screening experiment or previously reported research ( Hopen et al

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Shao-Ling Zhang and Shin Hiratsuka

Cultivars of the Japanese pear [Pyrus pyrifolia (Burm.) Nakai] have variable degrees of self-incompatibility (SI) and can be classified into at least three groups: strong, intermediate, or weak SI; as shown by the extent of self-pollen tube growth in the style, and the percentage of fruit set following self-pollination. Following self-pollination, the elongation of pollen tubes in the detached styles of `Kosui' and `Kikusui' became increasingly suppressed from 4 days before anthesis (–4 DAA) to 2 days after anthesis (2 DAA). Tube growth of `Kosui' was more suppressed than that of `Kikusui' during this period. In `Osa-Nijisseiki', however, the rate of tube growth did not vary with stage of stylar development, from –8 to 2 DAA. Pollen tubes elongated much better after cross-pollination than after self-pollination at all stages tested, and the extent of the elongation increased as the styles matured. The concentration of total S-protein (sum of two S-proteins per buffer-soluble protein) increased with stylar development, but the rate of increase varied with the cultivar. The rate was significantly greater in the strongly self-incompatible `Kosui' than in the moderately self-incompatible `Kikusui', and was slowest in the weakly self-incompatible `Osa-Nijisseiki' at all developmental stages. During stylar maturation, the concentration of S4-protein, which is common in all cultivars, was highest in `Kosui', followed by `Kikusui' and `Osa-Nijisseiki'. Thus, the cultivar differences in SI expression in the Japanese pear are determined about –4 DAA and appear to be regulated, in part, by the concentration of S-proteins produced in the style.

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Qi Zhang, Liqi Yang, and Kevin Rue

led to the differences in evapotranspiration (ET) rates and rooting depths in 10 creeping bentgrass cultivars. Of the 10 cultivars, Penncross showed the highest potential for drought tolerance because of its deep rooting habit and the highest ability

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Maren E. Veatch-Blohm, Dorothy Chen, and Matthew Hassett

abbreviations are as follows: ‘Ice Follies’ (IF), ‘Actaea’ (AC), ‘Dutch Master’ (DM), and ‘Tete-a-Tete’ (TT). Cultivars with the same capital letter are not significantly different according to Tukey’s honestly significant difference ( hsd ) ( P < 0.05) and