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Hamidou F. Sakhanokho, Kanniah Rajasekaran, Rowena Y. Kelley and Nurul Islam-Faridi

exist both at interspecific and intraspecific levels ( Eksomtramage et al., 2002 ; Mukherjee, 1970 ; Raghavan and Venkatasubban, 1943 ; Sharma and Bhattacharyya, 1958 ). Induced polyploidy is a valuable tool that offers some benefits for horticultural

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Kelly M. Oates, Thomas G. Ranney and Darren H. Touchell

morphological responses vary ( Horn, 2002 ). Furthermore, autotetraploids may also have a slower growth rate compared with their diploid cytotypes ( Chahal and Gosal, 2002 ). A greater understanding of the influence of induced polyploidy on fertility and

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Yinping Shi, Qiangsheng Wang, Jianming Yang, Congyi Sui and Qingrong Sun

To perform apple polyploid breeding the ways of inducing polyploidy pollen with temperature and chemicals were studied. Materials include 13 diploid cultivars: Red Chief, Dai Hong, Rose Red, Golden Delicious, Mollie's Delicious, Gala, Bella, Jonathan, Fuji, Qiu Kou Hong, and Yan Qing, OBIR-2T-47. Chemicals: Chloroform, N-nitroso-ethylurea. At the beginning of PMC meiosis, fruiting branching groups were covered with plastic bags to raise temperature or were treated with chemical. After covering, temperature during the day increased 2 °C, generally not lower than 0 °C. Whether branches received high temperature or chemicals treatment, polyploidy pollen was induced to produce. The pollen grain of CK is tricolporat, its polar view is triangular, and its diameter almost 40 μm, showing no difference in size. Rate of empty pollen grain is low. Pollen grains that were treated were different in size, and rate of empty pollen is high, part of pollen grains germinating colporat change into tetracolporat with a few polycolporat, its polar view is square, round, and oval. The diameter of large pollen grains was 45-48 μm, increased by 11-12%. Giant pollen grain are 50-68 μm, increased by 25%-70%. Rate of induction is different in different cultivars. For most cultivars, giant pollen grain is 0.3%-0.5%. Gala and OBIR-2T-47 were higher, reaching 2.5%-7%. Chemicals caused damage on cultivars. Delicious strains were easily damaged.

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Jessica Gaus, Dennis Werner and Shyamalrau Tallury

Segregation analysis of two different F2 families of stokes aster created by hybridizing two blue-flowered cultivars [`Peaches Pick' (PE) and `Omega Skyrocket' (OSR)] with the yellow-flowered cultivar `Mary Gregory' (MG) gave disparate results. The F2 progeny of PE × MG segregated in the expected 3:1 (blue:yellow) ratio. In contrast, all 782 progeny from the MG × OSR F2 family were blue-flowered. Flow cytometric analysis of the parents and F1 hybrids was conducted to determine if ploidy differences existed among the parents, as such differences could account for aberrant segregation behavior in the MG × OSR F2 family. Peak ratios suggested that MG and PE were diploid, OSR was tetraploid, and F1 hybrids of MG × OSR were triploid. Chromosome counts from root tip squashes confirmed that MG and PE were diploid (2n= 2x= 14), OSR was tetraploid (2n= 4x= 28), and F1 hybrid progeny of MG × OSR were triploid (2n= 3x= 21). Karyotype analysis also confirmed these results. We propose that the lack of recovery of yellow-flowered progeny in the MG × OSR F2 family is due to differences in parental chromosome number. These results document the first report of polyploidy in stokes aster, and suggest the absence of a triploid block in this species.

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Gyeong Ran Do, Ju Hee Rhee, Wan Soon Kim, Yun Im Kang, In Myung Choi, Jeom Hwa Han, Hyun Hee Han, Su Hyun Ryu and Han Chan Lee

cosmopolitan plant genus, Lilium lancifolium (syn. L. tigrinum ) is the only polyploidy-complex species in which diploid (2 n = 2 x = 24) and triploid (2 n = 3 x = 36) plants coexist naturally in the wild ( Hwang et al., 2011 ; Kim et al., 2005 ; Noda

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Ryan N. Contreras, John M. Ruter and Wayne W. Hanna

developing more compact forms. Induced polyploidy often results in the gigas effect of individual organs; particularly those with determinate growth such as sepals, petals, fruits, and seeds ( Stebbins, 1950 ). However, in the case of induced autopolyploids

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Renate Karle, Constance A. Parks, Maureen C. O'Leary and Thomas H. Boyle

Spontaneous chromosome doubling occurred in shoot apices of two diploid (2n = 22) Hatiora ×graeseri Barthlott ex D. Hunt (Easter cactus) clones and yielded stable periclinal cytochimeras with a diploid epidermis and tetraploid subepidermis. The cytochimeras produced disomic gametes (n = 22) and displayed tetrasomic inheritance at polymorphic isozyme loci. Diploid clones were highly self-incompatible (SI) but both cytochimeras were self-compatible (SC). Analysis of pollen tube growth in selfed or outcrossed styles revealed that polyploidy altered the incompatibility phenotype of pollen without affecting the incompatibility phenotype of the pistil. Morphological data (guard cell length, stomatal density, and pollen diameter), segregation ratios at isozyme loci, and fruit/seed yields indicate that S1 progeny are SC, nonchimeral, and tetraploid. Breakdown of the SI system in the cytochimeras was attributed to formation of compatible heteroallelic pollen. These results provide a rational explanation for the correlation between ploidy level and breeding behavior in cacti. Production of SC autotetraploid clones from SI diploids by chromosome doubling may be useful in development of cacti as fruit crops.

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Glendon D. Ascough, Johannes van Staden and John E. Erwin

during gamete formation, spontaneous somatic polyploidization, and wide hybridization cause plants to accumulate additional sets of chromosomes from closely or distantly related species. Polyploidy has been an important factor in plant evolution and is

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Cary J. Hebert, Darren H. Touchell, Thomas G. Ranney and Anthony V. LeBude

, high concentration oryzalin treatments on survival and polyploidy induction in callus cultures of Rhododendron ‘Fragrantissimum Improved’. In a second experiment, the influence of lower concentrations of oryzalin combined with longer treatment

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Kelly J. Vining, Ryan N. Contreras, Martin Ranik and Steven H. Strauss

for Sterility Breeding Induced polyploidy. Induced polyploidy is a widely used technique in plant breeding. Typically, meristems are treated with antimitotic agents such as colchicine or dinitroaniline herbicides such as oryzalin or trifluralin