本文を読む／探す
抄録
栽培イネにおける草型の改良は重要な育種目標のひとつであるにもかかわらず,一般には雑種後代で連続的かつ複雑な変異を示すため,その遺伝学的な知見は少ない。本研究では草型の構成要因のひとつである株の開張性(spreading stub)について遺伝子分析を試みた。日本型品種日本晴とインド型品種Kasalathの交雑F_1個体に日本晴を反復親として育成した戻し交雑後代個体BC_3F_1-11の自殖集団(BC_3F_2-11,n=50)は遺伝的背景が日本晴型に近づいたため株の開張性に関して単因子様の分離が認められた。BC_2F_3後代検定を実施したところ,この形質の遺伝子型評価が可能になり,その系統数の内訳は直立型:分離型:開張型=9:29:12(1:2:1,χ^2=1.64)であった。また分離系統内では開張個体と直立個体がほぼ3:1の割合で観察された。これらの結果から,この集団における株の開張性はKasalathが有する優性の1遺伝子によって支配されることが明らかとなった。またRFLPマーカーを用いた連鎖分析によってこの遺伝子座(Spk(t)と仮称)は第9染色体に座乗することが判明した。
Improving plant type is one of the principal objectives of rice breeding programs. However, Iittle information about the genetic basis of plant type is available. For progenies derived from indica/japonica crosses, the variation of plant type is continuous and complex, so genetic analysis of such traits is often difficult. This study was undertaken to clarify the genetic basis of spreading stub, an inferior plant type character for recent Japanese elite rice varieties. Two different plant types, spreading stub and erect, were observed in one population (BC_3F_2) derived from a selected backcrossed plant, in which a japonica variety, Nippon-bare, was the recurrent parent and an indica variety, Kasalath, was the donor parent. BC_3F_3 Iines derived from each BC_3F_2 individual were also classified into 3 distinct types, erect (9 Iines), spreading (12 Iines) and segregating into both types (29 Iines). Spreading type was observed about 3 times more frequently than erect type in each segregated line. These results suggest that spreading stub was controlled by a single dominant gene. Moreover the tentatively designated locus, Spk(t), was mapped, with RFLP markers, on chromosome 9.
