-generation hybrids ( Kamemoto et al., 1999 ). Differences in ploidy are a challenge to the development of new hybrids, and differences in chromosome number may prevent zygote development after pollination ( Singh and Hymowitz, 1987 ). Chromosome doubling is often
‘Woodbridge’. Although colchicine has proven effective, no study exists demonstrating the effectiveness of oryzalin in chromosome doubling of H. syriacus . Ploidy levels and chromosome numbers in Hibiscus have been confirmed in previous studies using
var. sativus [C (primary gene pool)] and C. hystrix [H (2n = 2x = 24, secondary gene pool) ( Chen et al., 1997 ). Because the F 1 progeny (2n = 2x = 19) derived from this mating were both male and female sterile, chromosome doubling was performed
, and will therefore have to undergo chromosome doubling to be useful in further breeding. Overcoming crossing barriers using chromosome doubling ( Contreras and Ranney, 2007 ) or embryo rescue ( Liu et al., 2007 ) may also lead to novel species
three kinds of intergeneric hybrids examined in the present study may be valuable as materials for further breeding of colchicaceous ornamentals. Although all of them showed low or no pollen fertility, artificial chromosome doubling might allow these
antimitotic agents colchicine and oryzalin on in vitro regeneration and chromosome doubling of diploid bananas ( Musa spp.) J. Hort. Sci. Biotechnol. 77 572 575 Geraci, G. 1978 Percentage of triploid offspring of cross-pollinated diploid polyembryonic citrus
in other applications such as identifying polyploid plants created through chromosome doubling of a cultivar of known ploidy level. Table 2. Stomatal guard cell length in diploid and triploid cultivars of Hydrangea macrophylla ssp
, and fertility in Hydrangea macrophylla HortScience 42 483 488 Kehr, A.E. 1985 Inducing polyploidy in magnolias J. Amer. Magnolia Soc. 20 6 9 Kermani, M.J. Sarasan, V. Roberts, A.V. Yokoya, K. Wentworth, J. Sieber, V.K. 2003 Oryzalin-induced chromosome
hybrids Euphytica 112 239 244 10.1023/A:1003994800440 van Tuyl, J.M. Meijer, B. van Dien, M.P. 1990 The use of oryzalin as an alternative for colchicine in in-vitro chromosome doubling of Lilium Lily Yrbk. North Amer. Lily Soc. 43 19 22 Vilà, M. Espinar
these protocols to diverse Magnolia taxa. These protocols also provide a platform for future experiments focused on the development of allopolyploids to restore fertility by chromosome doubling. Literature Cited Amoo, S.O. Finnie, J.F. Van Staden, J