Studies on the breeding of genus Coix X : Selection effect on tall culm strains of F_4 and F_5 generations between Hatomugi (Coix Ma-yuen ROMAN.) and Juzudama (Coix Lacryma-Jobi L.)(Agriculture)

1.ハトムギとジュズダマの雑種F_3系統群中より, 高稈で草丈の系統内変異の小さい系統を選抜してF_4系統を, さらにF_4世代より高稈系統を選抜してF_5系統をそれぞれ培養し, 草丈に関する選抜効果について検討を行なった。(i) F_4世代の草丈の系統内変異は概して小さく, 草丈が著しく分離する系統はF_3に比べて少ない。また, 高稈系統ほど草丈の変動係数は小さい。F_5世代においては, さらに分離系統は少なく, 草丈の変動係数も減少し, ほとんどすべての系統はハトムギおよびジュズダマの系統内変異よりも小さい。また, F_5世代の系統間分散はF_4世代に比べて減少し, 全系統平均値の両親植物に対する増加割合はF_4世代よりも大きい。(ii) F_4世代における草丈と主要形質間の相関では, とくに出穂期との間に正の有意相関が認められ, 遺伝相関も表現型相関とほぼひとしい。また, F_3世代までに認められた草丈と分けつ数との間の負の有意相関は認められない。草丈と花粉稔性および種子稔性との間にはそれぞれ正の相関が存在する。F_5世代においても, 草丈と出穂期との間には高い有意相関が認められ, 両形質の遺伝的関連性は強いが, 他の形質との間には有意相関は存在しない。(iii) F_4世代の親子相関および回帰による諸形質の遺伝力は, いずれも有意の値を示し, とくに出穂期は相関および回帰ともきわめて高い。この傾向は, F_4の系統にもまた系統群についてもほぼ同様であり, F_3の高稈選抜によっても諸形質の遺伝力はかなり高いと考えられる。F_5世代の諸形質の遺伝力は, 出穂期にのみ有意性が認められ, 本世代においても出穂期の遺伝力は大きい。他の形質にはいずれも有意性はなく, とくに草丈の遺伝力はかなり低い。すなわち, F_5世代における高稈性の選抜効果はF_2∿F_4世代ほど大きくなく, 草丈の固定度はかなり進んでいると考えられる。(iv)以上の結果, F_5系統中に230cm以上の高稈性で系統内分散が小さく, 栄養生長期間の長い晩生系統で, ハトムギ程度の分けつ数を有し, かつ, 90%以上の高稔性を有する系統を多数獲得することができたが, これらの育成系統は飼料作物としての利用はもちろん, 今後の研究素材としてもかなりすぐれたものと思考される。2.育成系統の種子発芽力はきわめて高く, 発芽率は雑種世代の進むにつれて向上し, F_6種子においては, 90%以上の発芽率を示す系統数は, 全系統の84%をしめている。この結果より, 育成系統の種子繁殖はきわめて容易であると考えられる。
From the results of statistic analysis of some morphological characters in F_3 generation between Hatomugi (Coix Ma-yuen Roman.) and Juzudama (Coix Lacrma-Jobi L.) (Murakami et al., 1964), it can be expected that we can breed up a tall, lately maturing strain of high yielding ability as fodder crops. The present paper deals with the selection effect on tall culm strains of F_4 and F_5 generations. 51 strains of F_4 were bred out of selection of tall F_3 strain and tall individual, and selection effect on characters was examined mainly with regard to plant height. Generally speaking plant height variance in F_4 strain was less than in F_3 and emergence of strain with tendency to plant height segregation was also few. Phenotypic and genetic correlation between plant height and heading date was high and significant. Significantly negative correlation between plant height and number of tillers recognized in former generation was not recognized in F_4. Heritability was estimated by means of correlation and regression between F_3 and F_4,and significantly positive correlation was recognized in many characters, especially in heading date. In F_3 family selected according to tallness, relationship between tallness and lateness of maturity was remarkable and heritability was estimated to be high. Among F_4 strains appeared many useful strains tall and of less segregation of plant height. Out of F_4 strain F_5 was bred up by means of more rigorous selection as to the tallness of plant. Though it depended on natural pollination within F_4 strain, there was scarcely influence of heterozygosis and the variance of plant heigh in the strain was little. When we compared the increase in mean plant height of whole strains of F_4 and F_5,taking parent plant of each as basis of comparision, it was greater in F_5 than in F_4. In this generation too, high correlation of 0.67 was still recognized between plant height and heading date but among other characters no correlation was recognized. Heritability of heading date was significant but it was not so in other characters. Germinating ability of seed became higher with the advance of generation up to more than 80%. And it was proved that the strain with tall height and high yielding ability is available by means of seed propagation.