大岩桐之花粉發芽、花型分類與遺傳

Pollen Germination, Classification and Inheritance of Flower Form in Gloxinia

大岩桐［Sinningia speciosa（Lodd.）Hiern, gloxinia］為重要的觀賞盆花，具多種花型，本研究利用現今商業流行之大岩桐品種，進行花粉發芽之研究，觀察花器進行花型分類及探討花型之遺傳。大岩桐依花瓣層數可分成單瓣（一輪花瓣）、半重瓣（兩輪花瓣）與重瓣（三輪花瓣）。半重瓣可分成類型1與類型2，其中類型1可依雄蕊的瓣化程度再分成三類：完全瓣化雄蕊（類型1-A）、花絲瓣化雄蕊合生（類型1-B）與未合生的退化雄蕊（類型1-C）。半重瓣類型2則有器官重複，亦即具兩輪花瓣與一輪雄蕊。重瓣（類型3）依雄蕊的瓣化程度可分成兩類：三層花冠筒且無雄蕊（類型3-A）與兩輪花冠筒與一輪未合生的退化雄蕊（類型3-B）。經解剖觀察可知，大部分類型的半重瓣與重瓣花是由雄蕊瓣化而來。取大岩桐絲織品－紅（Brocade Red）與大岩桐歡樂鈴－藍（Multi Bells Blue）之花粉於去離子水培養，其發芽率甚低，在BK培養基中參試品種花粉發芽之適合蔗糖濃度為10％－15％。分別取半重瓣‘Brocade Purple/White Bicolour’之正常雄蕊、花絲瓣化雄蕊與退化雄蕊三種類型之花粉，以內含10％蔗糖之BK培養基、於25℃黑暗下培養2小時。結果顯示正常花藥與花絲瓣化雄蕊之花粉外觀飽滿，皆可正常發芽；而退化雄蕊之花粉外觀乾癟，無法發芽。藉後裔檢定探討單、重瓣花型之遺傳控制模式。取單瓣親本自交或雜交，其後代皆為單瓣。以單瓣與半重瓣親本雜交，後代半重瓣與單瓣分離比為1：1。以半重瓣親本自交或雜交，其後代重瓣、半重瓣與單瓣分離比為1：2：1。推測大岩桐花型受D基因座所控制，當基因型為顯性同質結合DD時為重瓣花，異質結合Dd時為半重瓣花，而隱性同質結合dd時為單瓣花。

Gloxinia [Sinningia speciosa (Lodd.) Hiern] is a popular flowering potted plant grown for its large colorful flowers with various forms. This study aimed to observe floral organs, determine pollen germination and inheritance of flower form of gloxinia cultivars and their progeny. Gloxinia flowers could be categorized as single-flower (one corolla whorl, Type 0), semi-doubled flower (two corolla whorls, Type 1 and 2), and double-flower (three corolla whorls, Type 3). Type 1 was further classified as 1-A, 1-B, and 1-C with completely petaloid filament stamen and staminode, respectively. Type 3 can be divided into 3-A and 3-B, with corolla and staminode in the inner whorl. Most double- and semi-double flowers had inner petal whorls originated from stamens. Few pollens of ‘Brocade Red’ and ‘MultiBells Blue’ germinated in deionized water, while pollen cultured in BK media with 10%-15% sucrose germinated well. Pollen from normal stamen, stamen with petaloid filament and staminode of ‘Brocade Purple/White Bicolour’ were cultured in BK media with 10% sucrose for 2 h in dark. Results showed that pollen in anthers from normal and stamen with petaloid filament germinated, but not for those from staminode. Crossing or selfing single-flowered gloxinia species/cultivars resulted in all single- flowered progeny. Crossing semi-doubled flower and single-flowered parents showed semi-double flower and single flower segregation in a ratio of 1: 1. Crossing or selfing semi-doubled flower parents showed double flower, semi-double flower and single flower segregation in a ratio of 1 : 2 : 1. Flower form was proposed as controlled by a single allele (D, d). Genotype DD, Dd, and dd resulted in double, semi-double, and single flower, respectively.