ユキヤナギとシモツケの種間雑種における花器および開花特性(育種・遺伝資源)  [in Japanese] Floral Characteristics of Interspecific Hybrids between Spiraea thunbergii Sieb. ex Blume. and S. japonica L. fil.(Breeding & Germplasm Resources)  [in Japanese]

ユキヤナギSpiraea thunbergii Sieb. ex BlumeとシモツケS. japonica L. fil.との種間雑種を育成し,雑種個体の花芽の発育特性,花器の形態的特性,花色の特性を両親と比較した.1)雑種の腋芽の花芽分化は12月中旬から始まり,1月中旬に完了し,2月から花房分化が始まり,4月中旬に開花した.雑種の開花時期は両親の中間で,ユキヤナギよりも遅かったのは花芽形成時期が遅かったことと関係していた.2)雑種における雄ずい数,開花時期,1花序あたりの花数,花色,雄ずい長および花柱長は両親の中間的特性を示した.一方,花弁の形,花弁の長さ,花径はユキヤナギに類似し,花の着生状況や花序はシモツケに類似していた.3)雑種の全アントシアニン含量はシモツケに比べて少なく,花色は桃色を呈していた.雑種にはシモツケの6つの構成色素(Unknown, Cy3Ga, Cy3G, Cy3Ara, Pg3G, Mv3G)のうち4つのシアニジン系色素(Unknown, Cy3Ga, Cy3G, Cy3Ara)の色素が導入され, Cy3GaとUnknownが主要色素であった.花弁の色相の変化にはPg3GとMv3Gの量が関係していると考えられた.さらに,雑種の花弁は老化すると花色が退化するが,これは主要色素であるCy3Gaの減少が関与していた.よって,Cy3Gaは雑種の主要色素であり,色の濃淡に大きく影響していることが明らかになった.

We investigated the flower characteristics of interspecific hybrids between Spiraea thunbergii Sieb. ex Blume. and S. japonica L. fil. via ovule culture. The flower bud differentiation of hybrid plants started in December and the flower cluster formation started in February, then flowered in the middle of April. The flowering period of hybrid plants was 2 months from April to May, which was the intermediate between S. thunbergii and S. japonica. In hybrid plants and S. japonica, the flower setting was observed in the terminal of a current shoot elongated in the present year. Although the inflorescence of S. thunbergii was the unbel type, that of hybrid plants and S. japonica showed the corymb type. In the hybrid plants, the size of style, the number of stamen and the number of flowers per one inflorescence showed intermediate values between S. thunbergii and S. japonica. The color of petals in S. japonica was deep pink or red, while the hybrid plants had pink petals. Total anthocyanin concentration in petals of the hybrid plant was lower than that of S. japonica. Six types of anthocyanin (Cy3Ga, Cy3G, Cy3Ara, Pg3G, Mv3G, unknown) were detected in the petals of S. japonica, and the hybrid plant had four cyanidin pigments (Cy3Ga, Cy3G, Cy3Ara, Unknown) among six anthocyanins contained in S. japonica petals. The amounts of Pg3G and Mv3G seem to cause changes in the petal hue of S. japonica and hybrid plants. Furthermore, the fading of petals in the hybrid plant through flower senescence was caused by the marked decrease of Cy3Ga, which was one of main anthocyanin in hybrid plant.