| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Aneuploids have been useful for studying the genetics of many plant species and have possibility to be used for plant breeding. Firstly, in order to investigate the genic balance influenced by addition of an extra chromosome to diploid and haploid complements, an experiment was carried out on the production of trisomic (2n+1) and disomic haploid (n+1)plants in Nicotiana sylvestris (n=x=12). F_1 plants between triploid and diploid were backcrossed with the diploid plants. Sixty one trisomic plants were selected from the B_1 progenies. These trisomic plants were grouped into 12 types by the leaf shape and flower morphology. The anther culture was performed using the 12 types of trisomics. Among the obtained disomic haploids 5 types of plants developed frower organ. The flower of disomic haploid derived from B220 trisomic plant was conspicuously small and malformed, while the corresponding trisomic plant produced normal and remarkably larger flowers and leaves than the normal diploid. Thu
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s , trisomic line B220 will be very useful as a cultivar. However, in seed-propagated species, the low transimission of the extra chromosome has prevented such plants from becoming agriculturally useful cultivars. In line B220, the transfer of the extra chromosome in 2n x 2n+1 crosses was very low. This was due to the delayed development of n+1 pollen grains, which are not full maturity at the time of anthesis. The transfer of the extra chromosome in 2n x 2n+1 crosses was increased by a 1 day delay in pollination and also by pollination of small pollen grains selected through nylon meshes. Especially, pollen selected by using 30 and 25 m nylon meshes induced an extremely high transfer of the extra chromosome, namely 51.9% and 70.4%, respectively. Secondly, pollen grains in the anthers of disomic haploids of B220 treated before culture with physical mutagen such as X-rays, may be a useful method to induce the duplication of a chromosome segment which induces large leaf and flower. Doubling of genome may result in homozygous plantlets in the portion of duplicated chromosome segment. We realized many chromosome aberrations in plantlets induced by the anther treated by X-rays. No single plant with a useful duplication of the chromosome segment for agronomic character, however, has been achieved until now. It seems that in order to attempt to produce a specific duplication which is useful agriculturally, a huge number of translocations will be required. Less
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