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nulliplex. Indeed, plants that are heterozygous for the AST locus will express the astringency trait in fruit flesh (non-PCNA type; Ikeda et al., 1985 ; Yamada and Sato, 2002 ). Cultivated persimmon is hexaploid (2 n = 6 x = 90) ( Namikawa and Higashi

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breeding lines of L. camara , triploids were found to be the most male sterile of the ploidy levels, followed by hexaploids, pentaploids, tetraploids, and diploids ( Czarnecki et al., 2014 ). In addition, elite cultivars were found to vary widely in male

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The purpose of this study was to compare the relative fecundity of tetraploid × hexaploid and hexaploid × tetraploid crosses in blueberry. Four types of crosses were made using cultivars and advanced breeding lines consisting largely of V. ashei Reade (6×) and V. corymbosum L. (4×). Fruit set, number of developed seeds per ripe berry, and number of seedlings per pollinated flower were determined. Tetraploid × hexaploid crosses averaged as high in percent fruit set as tetraploid × tetraploid crosses, but seed number per ripe fruit was only 29% as high and seedling number per pollinated flower only 35% as high. Hexaploid × tetraploid crosses, by contrast, set only 48% as much fruit as hexaploid × hexaploid crosses. Despite reduced fruit set, hexaploid × tetraploid crosses averaged almost as high in number of seedlings produced per pollinated flower as the reciprocal cross. In both types of cross, the success rate strongly depended on the particular genotypes used in crossing. The overall success rate from crosses between tetraploid and hexaploid clones was 2.32 seedlings per pollinated flower, which is high enough to allow production of large pentaploid populations for use in breeding.

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Five nutrient solutions were evaluated in the greenhouse to determine which solutions would allow detached culms of Pennisetum to produce seed. The genotypes tested originated from the hybridization of Pennisetum glaucum L. (Pearl millet) × P. pennisetum Schum. (elephantgrass). The solutions were water, Hoagland's, sucrose, sucrose + hydroxyquinoline sulfate (HQ), and Hoagland's + sucrose + HQ. Neither the water nor the Hoagland's solution supported high seed set. Although the sucrose solution enhanced seed production, the seeds were low in weight and did not germinate well. The best nutrient solutions were 2% sucrose + 0.02% HQ or Hoagland's + 2% sucrose + 0.02% HQ. The four genotypes used differed substantially in seed production, but all produced seed, with germination >25%. This result indicates that the cut-culm technique is a possible way of getting recurrent restricted phenotypic selection seed in Pennisetum hexaploid hybrids.

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Vaccinium ashei (6x) /V. corymbosum (4x) pentaploid hybrids backcrossed to V. ashei yield aneuploid progeny ranging in chromosome number from 5x to 6x levels. Six backcross aneuploids having chromosome numbers of 2n = 61, 62, 64, 66, 68, and 70 were selected from this backcross and crossed in a complete diallel mating design and backcrossed (as female parents) to two V. ashei cultivars and an interspecific hexaploid hybrid. Fertility variables measured were percent fruit set, total seed per berry, developed seed per berry, percent developed seed per berry, percent seed germination, developed seed per pollination, and seedlings per pollination. A significant linear and positive relationship was found between chromosome number and all seven fertility variables. However, regression accounted for 30% or less of the variation among crosses. Diallel analysis revealed that general combining ability was the major contributing effect for all seven variables, followed by reciprocal effects. Specific combining ability was not significant. The second backcross to the hexaploid level suggested significant effects due to both the BC1 aneuploid and hexaploid genotypes and to a significant genotype × genotype interaction for three of the variables. All six aneuploids were either fully or partially self-sterile. The findings of this study substantiate earlier suggestions that pentaploids in blueberry can be used to facilitate bilateral transfer of characteristics between the tetraploid and hexaploid levels in blueberry.

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‘Nocturne’ is a dark-fruited, hexaploid blueberry selection with significant (50%) rabbiteye ( Vaccinium ashei Reade, syn. Vaccinium virgatum Aiton) ancestry for use as a specialty market plant for homeowner, landscape, and ornamental use

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Seed development of blueberry (Vaccinivm spp.) from pollination to fruit maturity was investigated for Florida selections ‘4-15’ and ‘4-71’ (2n=4x=48); and Bluegem’ (2n=6x=72). Embryo abortion was observed in each immediately following fertilization, at the end of stage I of fruit development, and during early stage II of fruit development.

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The efficacy of ploidy breeding using unreduced pollen in japanese persimmon (Diospyros kaki Thunb.) is not high because of the low frequency of unreduced pollen in most cultivars. This study was conducted in 2002 and 2003 to determine if the exposure to a low temperature before flowering could enhance the unreduced pollen formation in five cultivars of japanese persimmon including two cultivars that barely produce unreduced pollen under the field condition. The results showed that low-temperature treatment (4 °C for 48 hours) increased the occurrence of unreduced pollen at 15 to 17 and 17 to 18 days after the end of the low-temperature treatment in 2002 and 2003, respectively, in all five cultivars tested. Naturally occurring temperatures below 5 °C in the field also appeared to enhance the unreduced pollen formation in the cultivars that naturally produce unreduced pollen in the field.

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The change from asexual to sexual propagation for annual and perennial bedding plants has been successfully accomplished for floral crops, e.g., Pelargonium. Seed-propagated cultivars do not necessarily possess the clonal uniformity of vegetatively propagated cultivars. In the development of F1 hybrid garden chrysanthemums, this lack of uniformity was assessed with the use of consumer sensory evaluations. Seedlings (n = 10–20 plants/cross) were transplanted for field trials in St. Paul and five Minnesota branch stations each year during 1988–94 to test for G × E. Early flowering F1 hybrids, developed from inbred parents with general combining ability, were evaluated for flowering earliness, plant uniformity, and a general rating. Consumer rankings of top performers were not significantly different (5% level) from mum breeders. The top performers for all three ratings were selected each year for repeat evaluation the next year. The two highest performing F1 hybrids were submitted for All American Selection Trials in 1995.

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Interspecific crosses with Fragaria moschata (6x) have been hampered by ploidy level differences, poor seed set, and extremely poor seed germination. Modification of pollination practices, embryo rescue, and use of several genotypes has allowed over 80 synthetic tetraploids to be created from 14 cross combinations. Germplasm for the experiment consisted of eight selections of F. moschata (6x), two of F. nubicola (2x), and two of F. viridis (2x). Both 2x × 6x and 6x × 2x crosses were performed. Initially, negligible seed set occurred on F. nubicola and F. viridis when multiple flowers per truss were pollinated. When only one cross was performed per truss, with other flowers removed, seed set was greatly enhanced. F. moschata was much more tolerant of multiple crosses per truss. The crossing combination of F. moschata × F. nubicola gave the worst seed production. Other species combinations were capable of producing good seed set with noticeable differences between individual selections. When achenes were halved, only 1% appeared normal, 2% were underdeveloped or shrunken, the remainder were empty. Many of the malformed and most of the normal embryos germinated using the cut achene method. Achenes were surface-sterilized, cut in half, and placed on MS media with activated charcoal (3g·L–1), sucrose (30g·L–1), and no hormones. Germination occurred only from achenes from fully ripened fruit. Viable hybrids were obtained from 2x × 6x as well as 6x × 2x crosses. Fragaria viridis–F. moschata hybrids closely resembled F. moschata while F. nubicola–F. moschata hybrids were more intermediate in leaf morphology.

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