The remote hybridization and polyploid breeding in genus Rhododendron, so called azaleas and rhododendrons

杜鹃花属由五个亚属组成。四个亚属之间进行了不同的亚属间杂交；杜鹃花亚属杜鹃花组的膜花属、杜鹃花属、五花属和鹤尾属，以及种间或品种间的远缘杂交。在这些杂交组合中，成功地进行了各种杂交，获得了许多蒴果，即Hymenanthes Rhododendron（或反向）、Hymenanthes Pentanthera、Tsutsutsi Pentanthera和Rhododendron Pentanthera。然而，覆膜杜鹃和五色杜鹃的种子都无法发芽和杂交，五色杜鹃、五色杜鹃和鹤冢杜鹃甚至都无法形成蒴果。结果表明，属杜鹃花的种与种之间的杂交比属与亚属之间的杂交更成功，但成功程度不如属与亚属之间的杂交。由于杜鹃花在进化过程中产生了遗传分化，属与属之间的杂交更为特异。从膜ananthes Rhododendron和Hymenanthes Pentanthera获得的后代有望产生优秀的黄色品种，而几乎所有来自Tsutsutsi Pentanthera的后代都不能形成叶绿素，因此需要进行更广泛的杂交。从杜鹃花内杂交获得的后代也有望产生具有优秀黄色或蓝色花朵的形式。在后一种情况下，引入粉红色形式的细胞质显示出更旺盛的生长。曾尝试用普通秋水仙碱处理产生多倍体，但由于鹿儿岛夏季太热，处理过的植株无法存活，因此未能成功。因此，研究了组织培养诱导多芽再生的方法。在培养基中加入细胞分裂素后，多重产烟是可行的。在初步试验中，经0.05%秋碱处理3 ~ 5d，获得多倍体植株。少

Genus Rhododendron consists of five subgenera. Various intersubgeneric hybridizations were conducted among four subgenera ; Hymenanthes, Rhododendron, Pentanthera and Tsutsutsi along with interspecific or remote hybridizations between species and/or cultivars belonging to section Rhododendron of subgenus Rhododendron.Of these various hybridizations following cross combinations were succeeded and many capsules were obtained, that is, Hymenanthes Rhododendron(or reverse), Hymenanthes Pentanthera, Tsutsutsi Pentanthera and Rhododendron Pentanthera. However, seeds of Rhododendron Hymenanthes and those of Rhododendron Pentanthera failed to germinate and cross combinations, Pentanthera Hymenanthes, Pentanthera Rhododendron and Tsutsutsi Rhododendron even failed to produce capsules. As being expected, hybridizations between species and/or cultivars belonging to Rhododendron were more successful than those between subgenera, although the degree of success was inferior as compared with interspe … More cific hybridizations within Hymenanthes, Pentanthera or Tsutsutsi because of genetic divergence attained in the process of evolution in Rhododendron. The offsprings obtained from Hymenanthes Rhododendron or Hymenanthes Pentanthera were expected to produce excellent yellow cultivars, whereas almost all of those from Tsutsutsi Pentanthera failed to form chlorophyll and thus more extensive hybridizations would be needed. The offsprings obtained from crosses within Rhododendron were also expected to produce forms with excellent yellow or blue flowers. In the latter case introduction of cytoplasm of pink forms was revealed to afford more vigorous growth.An attempt to produce polyploid was done using ordinary colchicine treatment, but it failed because summer of Kagoshima was too hot for survival of treated plants. Therefore, tissue culture was examined in which multiple shoot regeneration could induce. With the addition of cytokinins into media multiple soot production was revealed to be feasible. In the preliminary experiment, plantlets which seemed to be polyploid were obtained through 0.05% colcemid treatment for 3 to 5days. Less