Fundamental studies for cross breeding in taro

本研究的目的是获得芋杂交育种的基本发现。得到的主要发现如下。孟加拉野生二倍体芋头花粉母细胞减数分裂相对正常，花粉育性高。这些野生芋头开花结果很好。人工杂交获得的种子容易发芽。这些结果表明，这些野生芋头具有较高的种子繁殖能力。在这些实验中，获得了大量的自交和杂交苗。自交和杂交苗除含有二倍体外，还含有低频率的三倍体。这证明了三倍体芋头起源于自交和二倍体之间的杂交。通过对三倍体杂交种的同工酶分析，表明形成三倍体芋头有两种途径。这两种方式分别是：1)未还原的雌配子与还原的雄配子合子；2)还原的雌配子与未还原的雄配子合子。对日本和国外芋头品种/材料进行同工酶分析，为阐明日本侧块茎品种（三倍体品种）的起源提供了一些线索。茎尖培养有利于芋头离体植株的长期保存。建议采用简单冷冻法对芋头进行低温保存。

The purpose of the present study was to obtain the fundamental findings for cross breeding in taro. The main findings obtained are shown as follows.Meiosis of pollen mother cells was relatively normal and pollen fertility was high in wild diploid taros from Bangladesh investigated. These wild taros flowered and fruited well. The seeds obtained by artificial crossings germinated easily. These results indicated that these wild taros have high ability to perform seed propagation. In these experiments, a large amount of selfed and crossed seedlings were obtained. Both the selfed and crossed seedlings contained triploid ones with low frequency in addition to diploid ones. This proved that triploid taros originated in selfing and crossing between diploid ones. Through isozyme analysis of the triploid hybrids, it was indicated that there are two ways of forming triploid taros. These two ways are 1)zygosis between unreduced female gamate and reduced male gamate and 2)zygosis between reduced female gamate and unreduced male gamate.The data obtained by isozyme analysis using Japanese and foreign varieties/accessions of taro gave some clues to clarify the origin of the Japanese lateral tuber varieties(triploid varieties).Shoot apex culture was revealed to be useful for long term preservation of taro plants in vitro. The simple freezing method was suggested to be suitable for cryopreservation of taro.