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H.M. Wallace, B.J. King and L.S. Lee

Pollen source is known to affect the fruit size and quality of 'Imperial' mandarin, but no study has determined the appropriate orchard design to maximize the beneficial effects of pollen source. We determined the parentage of seeds of 'Imperial' mandarin using the isozyme shikimate dehydrogenase to characterize pollen flow and the effect on fruit size in an orchard setting. Two blocks were examined: 1) a block near an 'Ellendale' pollinizer block; and 2) an isolated pure block planting. Fruit size and seed number were maximum at one and three rows from the pollinizer (P ≤ 0.05). Isozyme results were consistent with all seeds being the result of fertilization by the 'Ellendale' pollinizer. In the pure block planting, fruits in rows 5-11 inside the block were very small with no seeds. This indicates poor pollen flow resulting in a reduction in fruit quality for the pure block. These results emphasize the importance of pollinizers in orchard design, and bees in orchard management. They suggest that each row should be planted no more than three rows from the pollinizer to maximize the benefits of the pollen parent in self-incompatible cultivars such as 'Imperial'.

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Chih-Cheng T. Chao, Jinggui Fang and Pachanoor S. Devanand

Production of seedless mandarins such as `Nules' clementine mandarin (Citrus clementina Hort. Ex Tan.) and `Afourer' mandarin [C. sinensis (L.) Osbeck × C. reticulata Blanco] is increasing in California as consumers' interest in seedless, easy peeling, and good tasting mandarins increases. The fruit would produce seeds if cross-pollination with compatible pollen source occurred. It is almost impossible to prevent cross-pollination between compatible mandarin cultivars by honeybees (Apis mellifera L.) within the multi-faceted agricultural environment in California. To produce seedless mandarin, growers either plant a single cultivar in a large solid block or try to use pollen-sterile navel oranges (C. sinensis) or satsuma mandarins (C. unshiu Marco.) as buffers to prevent cross-pollination. The question of how many rows of buffer trees or spacing can effectively prevent cross-pollination by honeybees between compatible mandarins is unclear. We initiated a study using fluorescent-labeled AFLP markers to determine the pollen parentages of `Nules' clementine seedlings and `Afourer' mandarin seedlings from two orchards in California. The longest distance of pollen flow at an orchard near Madera was 521 m. The pollen of `Minneola' tangelo (C. reticulata × C. paradisi Macf.) was able to disperse across a minimum of 92 rows of `Lane Late' navel oranges plus two rows of `Afourer' mandarins to pollinate `Afourer' mandarins. We also found that all the seedlings of `Nules' clementine mandarin at an orchard near Bakersfield had been pollinated by `Afourer' mandarin pollen. The pollen of `Afourer' mandarin was able to disperse up to distances between 837 and 960 m to pollinate `Nules' clementine. The pollen dispersal distance found in this study was at least 16 times longer than previously reported in a citrus orchard. Growers need to consider a much larger space or buffer rows to prevent cross-pollination and produce seedless mandarins in California.

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S. Alan Walters and Jonathan R. Schultheis

several studies have focused on pollen movement of cucurbits, little has been done to place this in the context of pollinator flight patterns and none have determined pollen flow of watermelon. Therefore, a morphologically marked watermelon genotype was

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Kristen R. Hladun and Lynn S. Adler

, 1987 ; Fronk and Slater, 1956 ; McGrath, 2002 ). Pollen flow between blue hubbard and butternut squash could interfere with pollination. Blue hubbard can cross with butternut squash, but the resulting fruits contain a high proportion of nonviable

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Joshua H. Freeman, G.A. Miller, S.M. Olson and W.M. Stall

Blackville, SC, and Citra, FL, was low overall and this may be why there was no effect by the pollenizers. The experimental design was successful in reducing pollen flow out of experimental plots as indicated by minimal fruit set in control plots. Lack of

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Virginia Pinillos and Julián Cuevas

in open- versus cross-pollination in either year, with the only exception being the trees directly receiving the cross-pollen flow from the duster (Row 1) in Sorbas, in which a slight but significant increase in fruit set was noticed ( Fig. 1 ). Cross

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Daiichiro Miyajima

The causes of low production of seeds capable of producing double-flowered plants and of high production of seeds capable of producing single-flowered plants were investigated in zinnias (Zinnia violaceu Cav.). Poor pollination was a major cause of the low seed set. A tubular floret produced abundant pollen; however, the pollen flow to ray stigmas was limited due to the infrequent visitation by pollinators. Moreover, in the double-flowered capitula, newly opened ray petals overlapped on the pistils that unfolded the previous day. These phenomena were considered to cause low seed set in double-flowered plants. Actually, capitula with more tubular florets produced more seeds than those with fewer tubular florets. Pollen germination and plants near zinnias had additional possible influences on seed production of double-flowered zinnias.

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Fabio Orlandi, Carlo Sgromo, Tommaso Bonofiglio, Luigia Ruga, Bruno Romano and Marco Fornaciari

highlight in particular the influence of temperature requirements and consequent reproductive structures maturation/pollen emission phases ( Alcalá and Barranco, 1992 ; Fornaciari et al., 2005 ; Orlandi et al., 2005a ). The study of pollen flows through

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Julie Graham, Mary Woodhead, Kay Smith, Joanne Russell, Bruce Marshall, Gavin Ramsay and Geoff Squire

were identified in wild populations and 17 alleles in commercial cultivars that had the potential to enter population 12 through pollen flow detected in the progeny or by seedling recruitment from another population. Additional new alleles may also be

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Trenton Hamada, Irene Terry, Robert Roemer and Thomas E. Marler

horizontal distance of pollen flow in each habitat. We then compared results for C. miconesica ’s pollen to those of entomophilous cycads and several native zoophilous angiosperms to ascertain whether there are any correlations between the potential mobility