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Yayan Feng, Leifeng Xu, Panpan Yang, Hua Xu, Yuwei Cao, Yuchao Tang, Suxia Yuan and Jun Ming

, and its low fertility has limited its application for breeding. Chromosome doubling could improve the genetic adaptability, fertility, and nutritive value of this species ( Chen and Kirkbride Jr., 2000 ; Dhooghe et al., 2011 ; Gomes et al., 2014

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Justin A. Schulze and Ryan N. Contreras

polyploidy, or chromosome doubling, can be accomplished in several ways. Commonly, seedlings or shoots tips are treated with colchicine (in vitro or in vivo). Colchicine, a mitotic spindle inhibitor affecting chromosome separation during mitosis, has been

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Ryan N. Contreras and Luigi Meneghelli

combination(s) that resulted in the greatest percentage of chromosome doubling. Fig. 1. Prunus laurocerasus ‘Otto Luyken’ explant during treatment in culture tubes (25 × 150 mm) filled with 10 mL of solidified MS medium into which the base of the explant was

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Marijana Jakše, Pablo Hirschegger, Borut Bohanec and Michael J. Havey

breeding programs, several obstacles still restrict its efficiency. Critical parameters include the role of genotype, the heritability of high gynogenic responsiveness, the chromosome doubling efficiency, and the male fertility of doubled haploid lines

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Bruce L. Dunn and Jon T. Lindstrom

these chemicals for chromosome doubling varies depending on the plant species, concentration levels, and treatment duration. Restored fertility, increased flower and leaf sizes, and shortened internodes often accompany ploidy manipulation ( Pryor and

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Ryan N. Contreras

gametes or spontaneous chromosome doubling in embryonal initials ( Khoshoo, 1959 ). Only diploids and tetraploids were recovered in the current study. In contrast, Contreras et al. (2010) observed 9.3% mixoploids after 30 d treatment of japanese

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Guo-Gui Ning, Xue-Ping Shi, Hui-Rong Hu, Yan Yan and Man-Zhu Bao

Jacobsen, 2003 ; Thao et al., 2003 ). Since the discovery by Blakeslee and Avery (1937) of the effectiveness of colchicine for the achievement of chromosome doubling in plants, colchicine has been successfully used to obtain polyploid plants of many

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Mohammad Majdi, Ghasem Karimzadeh, Mohammad A. Malboobi, Reza Omidbaigi and Ghader Mirzaghaderi

( Colchicum autumnale ), for chromosome doubling has opened a large reservoir of possibilities in polyploidization ( Hassawi and Liang, 1991 ). Although increasing the levels of secondary metabolites as a result of polyploidy induction has been reported for

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Ping Song, Wanhee Kang and Ellen B. Peffley

Regenerating calli of Allium fistulosum × A. cepa interspecific F1 hybrids were treated in vitro with colchicine. A factorial experiment (colchicine concentration × time) was used to recover tetraploids from calli treated with colchicine in vitro. Shoot production of regenerating calli following in vitro colchicine treatment decreased with increasing colchicine concentration and treatment time. Cytological analyses of root tip cells from regenerated plantlets showed that chromosomes of control plantlets (not treated with colchicine) were not doubled. Chromosomes of some plantlets regenerated from in vitro colchicine treated calli were doubled, resulting in tetraploids. Calli treated with 0.1 or 0.2% colchicine in BDS (Dunstan & Short, 1977) liquid medium for 48 or 72 hours yielded the highest number of tetraploid plantlets. These results demonstrate that in vitro colchicine treatment of regenerating calli of interspecific F1 hybrids is effective in recovering tetraploids.

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Grace M. Pietsch and Neil O. Anderson

Gaura lindheimeri is a diploid herbaceous perennial species native to Texas and Louisiana and winter hardy only to USDA hardiness zone 5. A potential source of winter hardiness is G. coccinea Pursh., a polyploid widely distributed in North America; of particular interest are autotetraploid populations of G. coccinea from Minnesota. To facilitate interspecific hybridization, a tetraploid G. lindheimeri would be advantageous. Two G. lindheimeri genotypes, MN selections 443-1 and 01G-02, were treated with two different antimitotic agents at two concentrations, trifluralin—15 and 30 μm and colchicine—0.25 and 1.25 mm, along with appropriate controls, to determine the frequency of chromosome doubling. Two-node stem sections were treated for 12, 24, or 48 h and then rooted and grown to flowering. Pollen diameter was measured as an indicator of chromosome doubling in cell layer LII, and morphologic characteristics (days to flower, flower size, plant height, inflorescence height, and plant width) were recorded for all plants. Chromosome doubling was not observed in any plant treated with trifluralin. Based on pollen diameter, genotype 443–1 only had chromosome doubling in the colchicine 1.25 mm concentration when treated for 12 h. All durations of colchicine at 1.25 mm were successful for genotype 01G-02 as well as a small percent treated with colchicine at 0.25 mm treated for 48 h. Autotetraploid plants (2n = 4x = 28) had larger flowers in both genotypes, and autotetraploid derivatives of genotype 01G-02 flowered earlier and were taller than diploid plants. Conformation changes from three-lobed to four-lobed pollen grains were observed when pollen diameter approached that expected of 2n pollen. Visual screening of pollen for conformation changes can quickly determine if chromosome doubling in cell layer LII has occurred. With the autotetraploid G. lindheimeri derived from colchicine application, crosses can be performed with autotetraploid G. coccinea to introgress cold tolerance. Additional breeding can also be done at the tetraploid level to develop new autotetraploid cultivars of G. lindheimeri.