Coix属の改良に関する育種学的研究-13-タイ国産Coixと本邦産CoixのF1雑種の形態ならびに細胞遺伝学的研究

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  • Coix 属の改良に関する育種学的研究 XIII : タイ国産 Coix と本邦産 Coix の F_1 雑種の形態ならびに細胞遺伝学的研究(農学部門)
  • Coixゾク ノ カイリョウ ニ カンスル イクシュガクテキ ケンキュウ 13 タイ コクサン Coix ト ホンポウサン Coix ノ F1 ザッシュ ノ ケイタイ ナラビニ サイボウ イデンガクテキ ケンキュウ
  • Studies on the improvements by means of breeding of the genus Coix XIII : Morphological and cytogenetical studies of F_1 hybrids between Thailand and Japanese Coix varieties (Agriculture)

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Abstract

The present paper deals with the investigation on the morphological characters and cytogenetical observation of F_1 hybrid between Thailand and Japanese Coix varieties. Sixteen varieties of genus Coix introduced from Thailand belong to Coix Lacryma-Jobi L. with twenty somatic chromosome number. According to the specific classification of genus Coix based on the shape of seed, these varieties are classified into four varieties, that is var. major, var. monilifer, var. typica and var. stenocarpa. Thailand varieties except two varieties were not recognized heading. The crossing was attempted between eight varietes of Thailand Coix recognized heading after short day treatment and Hatomugi (Coix Ma-yuen Roman.), Juzudama (C. Lacryma-Jobi L.) and its F_6 strain showed vigorous type in some morphological characters. F_1 hybrids in these crossing were obtained in nine among eleven cross combinations. In the early stage of development, the plant height of F_1 hybrid shows a tendency to vigorous like Thailand Coix varieties and F_7 strains, but F_1 hybrid showed heterosis in plant height in date of maturity. Heading of F_1 hybrid was recognized in seven cross combinations and setting seed was obtained in three combinations among them. This suggests that the gene for early maturity of Japanese Coix varieties was introduced to Thailand Coix varieties. In some F_1 hybrids, number of tillers and number of leaves were vigorous as compared with both parent plants. Generally the coefficient of variation of plant height of Thailand Coix varieties were larger than Japanese Coix varieties, and that of F_1 hybrid was distributed between them. From this result, it can readily be imagined that the Thailand Coix varieties were heterogenious condition for genes which determine the plant height. With a view to investigate of affinity between Thailand and Japanese Coix varieties, the authors have observed chromosome configurations and their frequencies in meiosis of PMC's of F_1 hybrid. The chromosome association in meiosis of Hatomugi and Juzudama was shown 10II in all divided cells, and their forms were closed bivalent, but in the F_7 strains and a few Thailand varieties 9II+2I was observed in about 10% cells. The chromosome configurations in the F_1 hybrids were observed five types with 0,2,4,6 and 8 univalent, but the most frequency of appearance was 10II among them. The frequency of univalent in divided cells are variable due to difference of cross combination. As to this phenomena, it would be recognized that there are difference of homology of chromosomes and variation of karyotypes between Coix varieties used in this experimant. From these morphological and cytogenetical investigation mentioned above, it will be concluded that the Thailand Coix varieties are very available as breeding materials for improvement of genus Coix.

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